Service TrainingSelf-study Programme 528The Natural Gas Drive in the Golf/Golf Estate TGI BlueMotion Design and Functiones, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ngAG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o eo th u ra a c s sility ab y li an pt cerrectness of i t to the co nf o r m spec atio h re n in witthi sd o cu m enht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig ht . C op yiFor the first time a Golf engine will combine natural gas drive and direct petrol injection. It is equipped with a EA211 1.4 l, 81 kW TGI* engine. Apart from the adaptations to the natural gas drive, it is identical to the 1.4 l, 90 kW TSI engine. The new EA211 engine family combined with BlueMotion means that the Golf TGI requires only 3.4 kg/100 km of natural gas with the 7-speed dual clutch gearbox and 3.5 kg/100 km of natural gas with the 6-speed manual gearbox. This equates to CO2 emissions of just 92 g/km and 94 g/km respectively.* The designation “TGI” is protected by trademark law by Volkswagen and denotes engines with natural gas drive.Properties of natural gas compared with other types of fueles, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ng Basis of comparison Pollutant emissions Premium-grade petrolPollutant emissions Fuel value Petrol-operated - Natural-gas-operated Fuels - comparison k s l w o a V g . e G n A A G do agen es n ksw ot g Vol y ua b d ran e s i tee r o h or ut ac a ssNatural gasPremium-grade petrol 12.00 kWh/kgCarbon monoxide (CO)Carbon dioxide (CO2)Natural gas 13.00 kWh/kgNitrogen oxides (NOx)Autogas 12.80 kWh/kgDiesel 11.80 kWh/kgility ab y li an pt ceAutogasrrectness of i t to the co nf o r m spec atio h re n in witPremium-grade petrolHydrocarbons (HC)Diesels528_002On the following pages, we will introduce you to the design and function of the natural gas drive in the Golf/Golf Estate TGI BlueMotion. You will find further information on the topic of natural gas in Self-study Programme no. 262 “Natural gas – an alternative fuel for motor vehicles”; no. 373 “EcoFuel Natural Gas Drive in Touran and Caddy” and no. 425 “EcoFuel Natural Gas Drive with 1.4 l 110 kW TSI Engine”.agen lksw Vo byAG.Prote cted bythi sd o cu m enThe self-study programme shows the design and function of new developments. The contents will not be updated.For current testing, adjustment and repair instructions, refer to the relevant service literature.2ht rig py Co t.c o p yri gh t. C op yiImportant NoteContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 The Golf/Golf Estate TGI BlueMotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4AG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o e Engine mechanics . . . . . . .ut.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . o.r . . . . . . . a a s s The 1.4 l 81 kW TGI engine (natural gas) . . . . . . . . . . . . . . . . . . . . . .c . . . . . . .ility ab y li an pt cees, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ng6 6 Adaptations to the engine mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7rrectness of i t to the co nf o r m spec atio h re n in witNatural gas drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 The natural gas drive in the Golf/Golf Estate TGI BlueMotion . . . . . . . . . . . . 8Engine management system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Engine control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Dash panel insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26thi sd o cu m enService . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 The special features of natural gas vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Special tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29AG.Test your knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30ht rig py Co t.agen lksw Vo byProte cted by c o py rig ht . C op yi3IntroductionThe Golf/Golf Estate TGI BlueMotionIt has a dual fuel vehicle drive system. This means it can be driven in both natural gas mode and petrol mode. If all conditions are met, the engine will always start and run in the more economical and environmentally friendlier natural gas mode. General vehicle data – natural gas • The fuel capacity of the natural gas tank is approx. 15 kg of natural gas at a maximum of 200 bar and an ambient temperature of 15°C In natural gas operation, fuel consumption is 3.4 kg of natural gas H* every 100 km and the range is approx. 440 km when combined with the 7-speed dual clutch gearbox DQ200 General vehicle data – petrol • • Capacity of petrol tank is 50 l petrol In petrol operation, fuel consumption is 5.0 l petrol every 100 km and the range is approx. 1000 km when combined with the 7-speed dual clutch gearbox DQ200•* Natural gas H (high) has a higher methane content than natural gas L (low). The higher the methane content, the better the natural gas quality and the greater the range.es, in part or in w l purpos hole ercia , is n m ot compe rm itte dun leAG. Volkswagen AG d agen oes ksw not l o V gu y b ara d nte ise r o eo h t u ra a c s sility ab y li an pt cerrectness of i t to the co nform spec a t i h re o n in wit thi sGas filler neck with non-return valveNatural gas fuel tanks 1 and 2 with fuel tank shut-off valves 1 and 2 N361 - N362r te o iva r rp fo g ndo c um en4ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t. C op yiPetrol – Fuel tanksDash panel insert with natural gas gauge G411, fuel gauge G1, natural gas mode warning lamp K192 and reserve fuel warning lamp K105Relay for gas shut-off valves J908es, in part or in w l purpos hole ercia , is n m ot compe rm itte dun leAG. Volkswagen AG d agen oes ksw not l o gu Gas distributor rail with gas yV b ara d e nte injection valves 1 4 N366 N369 is r o eo h ut and gas rail temperature and ra a c s spressure sensor GX21ility ab y li an pt cerrectness of i t to the co nform spec a t i h re o n in wit thi sr te o iva r rp fo g ndo c um ens528_004Electronic gas pressure regulator with high-pressure valve for gas mode N372 and tank pressure sensor G400 Exhaust system, finishes beside the petrol tank Catalytic converter coating, adapted to natural gas operationht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig h t . Co py i5Engine mechanicsThe 1.4 l 81 kW TGI engine (natural gas)This engine with engine code CPWA will be used in the Golf and Golf Estate starting from model year 2014. The only difference from the 1.4 l 90 kW TSI engine is the modified components for the natural gas drive.es, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nAG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o eo th u ra a c s sility ab y li an pt cerrectness of i t to the co nform spec at i h re o n wit in t hisTechnical features• •• • •You can find further information about this engine in Self-study Programme no. 511, “The New EA211 Petrol Engine Family”.Technical dataEngine code Design Displacement Bore Stroke Valves per cylinder Compression ratio Max. output Max. torque Engine management system Fuel CPWA 4-cylinder in-line engine 1395 cm3 74.5 mm 80 mm 4 Torque (Nm) 10.5:1 81 kW at 4800 - 6000 rpm 200 Nm at 1500 - 3500 rpm Bosch Motronic MED 17.5.21 Natural gas H Natural gas L with reduced range Super unleaded with RON 95 Three-way catalytic converter, one upstream broadband Lambda probe and one steptype Lambda probe downstream of the catalytic converter EU 6Torque and power diagram240 220 200 180 160 140 120 100 80 0 1000 3000 5000 7000 100 90 80 70 Power (kW) 60 50 40 30 20Exhaust gas aftertreatmentSpeed (rpm) s528_037Emissions standard6ht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig ht . C op yione engine control unit for natural gas and petrol operation electronic gas pressure regulator with a mechanical and an electronic pressure reduction stage gas distributor rail with temperature and pressure sensors optimised gas injection valve, which allows a start from -10 °C in natural gas operation adjusted quantity and composition of catalytic coating, in order to convert even very temperature-resistant methanedo c um ens528_006Adaptations to the engine mechanicsIn addition to cleaner fuel combustion, natural gas also has a higher anti-knock index compared with petrol. The octane number for natural gas H can be up to 130 RON. This allows an earlier ignition time without combustion knock. The efficiency increases and the combustion pressure and combustion temperature in the combustion chamber also increase. However, natural gas is very dry and does not have lubricating properties like petrol. All these factors place additional strains on the engine and require modifications to the engine mechanics.AG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o eo h ut ra a c s sility ab y li an pt ceThe die-cast aluminium piston is hard anodised in the first ring groove and the uppermost piston ring has a special coating. Both measures give increased wear resistance.es, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nPistons / piston ringsrrectness of i t to the co nform spec at i h re o n wit in t hisValve timings of the camshaftThe closing segment of the inlet and exhaust cams are not as steep. As a result, the valves are closed slightly more slowly and the mechanical load is reduced.Valves, valve guides, valve stem oil seals and valve seat insertsht rig py Co t.do c um enThe inlet and exhaust valves are nitrated, plated and have hardened shafts to make them more wearresistant. The material used for the inlet valve guides and all of the valve seat inserts has been adapted. The valve stem oil seals on the exhaust valves have two sealing lips with a reduced radial force. This increases oil flow and improves the lubrication between the valve shafts and the valve guides. The second additional sealing lip keeps the oil between the valve shafts and the valve guides when the valves are closing.agen lksw Vo byAG.Prote cted by c o py rig h t . Co py iHigh-pressure injectors 1-4 N30-N33 In petrol mode the high-pressure injectors are cooled by the flowing fuel (petrol). There is no cooling in natural gas mode. Since these valves protrude directly into the combustion chamber, impermissibly high temperatures would result. For this reason a graphitic Teflon ring with a high thermal conductivity is used.Exhaust gas turbocharger The high efficiency of the natural gas operation further reduces the energy content in the exhaust gas. Nevertheless, a smaller compressor wheel is used in order to achieve quick response characteristics from the turbocharger.7Natural gas driveThe natural gas drive in the Golf/Golf Estate TGI BlueMotionThe natural gas drive is the primary drive. If all conditions for natural gas operation are met, the engine will always start and run in natural gas mode. The driver does not have the option of switching back and forth between natural gas and petrol.Gas filler neck with filter and non-return valveNatural gas fuel tanks 1, 2 with tank shut-off valves N361, N362urposes, in part or in wh ole, cial p is n mer m ot p o c erm or e t a itte v i r d pun lewag olks yV b ed Support for natural ris gas ho t fuel tank au ssElectronic gas pressure regulator with tank pressure sensor G400 and highpressure valve for gas mode N372 k s l w o a V g . en AG en AGgu arrail Gas distributor an with gas rail tee temperature and pressure sensor or ac valves GX21 and gas injection N366-N369ility ab y li an pt cedoes notCoolant circuit connectionsrrectne s s o f i t to the co n form spec atio h re n wit i n thi sd o c um enUndercoatingConnecting piecer fo ngHigh-pressure natural gas line Low-pressure natural gas line to the gas distributor rail on engineagen lksw Vo byAG.ht rig py Co t.s528_007Petrol tankGas filler neckThe gas filler neck is located on the right-hand side of the vehicle under the tank flap beside the petrol filler neck. The high-pressure natural gas line is no longer screwed onto the gas filler neck, but welded, thus doing away with the leak testing position, which was hard to access. In addition, a non-return valve and a metal filter are located in the gas filler neck.8Prote cted by c o py rig ht . C op yiGas filler neck with filter and non-return valvePetrol filler neckMetal filters528_008 Non-return valveNatural gas fuel tankThe Golf TGI uses two identically sized natural gas fuel tanks made of steel. Each has a capacity of approx. 7.5 kg at a pressure of 200 bar and an ambient temperature of 15°C. The dead weight is approx. 44 kg per fuel tank. Three coats of paint are applied to the fuel tanks. This makes the fuel tanks more scratch-proof and resistant to corrosion in comparison with fuel tanks which only have two coats of paint.Metal support for fuel tankss528_009agen ksw Vol y b ed ris o th auNatural gas fuel tank 1 wage olks nA AG. Vurposes, in part or in wh ole, cial p is n mer m ot p o c erm or e t a itte v i r d pAttachmentun lessG do es n ot g ua 2 Natural gas fuel tank ran tee or acility ab y li an pt ceMetal bracketThe fuel tanks are attached to a metal support with the aid of two or three securing straps. This in turn is bolted to the body. To protect the paintwork against damage from the securing straps, a pad is inserted between the fuel tank and the securing strap. The disc springs provide permanent and appropriate pretension for the securing straps. They are divided into three packets of the same size. To ensure the correct alignment prior to attaching, the spring assembly is pretensioned to a certain limit.PadSecuring strap Disc springht rig py Co t.rrectne s s o f i t to the co n form spec atio h re n wit i n thi sd o c um enAG.Mark the installation position of the pads on the natural gas fuel tank and measure the position of the securing straps prior to removing the fuel tank. The securing straps must remain under tension. Make sure not to scratch the natural gas fuel tanks whilst unfastening them.agen lksw Vo byProte cted by c o py rig h t . Co py ir fo ngScrews528_0349Natural gas driveNatural gas linesAll natural gas lines on the high pressure side are made of steel and have an external diameter of 6 mm. The highlkswagen A G. Vo A G do agen es n ksw l ot g piece. The natural gas flows from the gas filler neck to the o pressure lines are all interconnected via a connecting yV ua db ran e s i connectingorpiece. From there it reaches the natural gas tfuel ee tank and the electronic gas pressure regulator via the h or ut ac a fuel tank shut-off valve. ss A flexible woven tube, which acts as a low-pressure gas pipe, and a stainless steel gas distributor rail are used on the low-pressure side.ility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nrrectness of i t to the co nform spec at i h re o n wit in t hisHigh-pressure sideLow-pressure sideGas filler neck with filter and non-return valveElectronic gas pressure regulatordo c um enGas distributor railFuel tank shut-off valvesHigh-pressure natural gas lines High-pressure natural gas line Connecting piece with non-return valve Flexible low-pressure natural gas lineThe high-pressure natural gas line from the distributor to the electronic gas pressure regulator consists of one line. There are no coupling points as with the eco up!10ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t. C op yis528_033Connecting piece with non-return valveThe various components of the natural gas system are interconnected via the connecting piece. Two high-pressure natural gas lines lead from here to the natural gas fuel tanks, another leads to the electronic gas pressure regulator and a fourth to the natural gas filler neck. A non-return valve is fitted in the connection for the natural gas line from the gas filler neck. Two valves close the natural gas system externally in tandem with the non-return valve after each refuelling.Prote cted by c o py rig h t . Co py ies, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nAG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o eo h ut ra a c s sTo natural gas fuel tank 2ht rig py Co t.ility ab y li an pt cerrectness of i t to the co nform spec at i h re o n wit in t hisTo natural gas fuel tank 1To the electronic gas pressure regulatordo c um enAttaching the natural gas linesA double clamping ring connection is used to attach the high-pressure natural gas lines to the components. When tightening the union nuts, the rear clamping rings are squeezed over the front ones and also tighten the lines to the thread. The nuts should be tightened to a specific torque. A supporting chock on the screw serves as a stop. The supporting chock simultaneously protects the connection against heaving soiling.Loose double clamping ring connection Front clamping ring Union nut Rear clamping ringThe supporting chock must line up precisely with the union nut.s528_044 Union nutagen lksw Vo byAG.Non-return valve s528_057 from the natural gas filler necks528_043 Stop on the screw Tightly screwed double clamping ring connection Screw Stop on the screw11Engine management systemSystem overviewIn the system overview you can see the sensors and actuators which have been added to the engine management system for the natural gas drive.SensorsActuatorsHigh-pressure valve for gas mode N372 Tank pressure sensor G400 Engine control unit J623 Relay for gas shut-off valves J908 Tank shut-off valves 1 and 2 N361–N362Gas rail temperature and pressure sensor GX21Gas injection valves 1 to 4 N366-N369n AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed s i tee r o h t or Electronic power control u ac a ss fault lamp K132Powertrain CAN data busility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nConvenience CAN data busExhaust emissions warning lamp K83rrectness of i t to the co nform spec at i h re o n wit in t hisDiagnosis connectionControl unit in dash panel insert J285Data bus diagnostic interface J533Natural gas gauge G411 Natural gas mode warning lamp K192 Fuel gauge G1 Reserve fuel warning lamp K105s528_015do c um en12ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t . C op yiThe engine control unit is built into the engine compartment between the vehicle battery and fuse holder B on the left-hand side of the vehicle. It manages all functions of petrol and natural gas operation. In addition, the on-board diagnostic system can also perform natural gas drive checks for all exhaust-relevant components of the natural gas operation.es, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ngEngine control unit J623n AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed s i tee r o h t or u ac a ssility ab y li an pt cerrectness of i t to the co nf o r m spec atio h re n in witThe on-board diagnostic system enables you to switch manually between natural gas and petrol operations. This can be helpful when searching for faults.ht rig py Co t.s528_016thi sd o cu m enIf the vehicle is started with a coolant temperature below -10 °C, a cold start function for the gas injection valves is activated in petrol mode. This involves adding natural gas – measured at 12% of the total quantity of fuel required – to the petrol whilst the high-pressure valve for gas mode is closed, until the natural gas from the gas distributor rail is combusted. At this point the gas injection valves will be continuously energised for 45 to 90 seconds subject to the ambient temperature. As a result, the temperature in the valves increases by approx. 35 °C and prevents the gas injection valves from getting jammed. Next the high-pressure valve for gas mode is activated, pressure starts building up again in the gas distributor rail and it switches over to natural gas operation as quickly as possible.Emergency start strategyIf it is not possible to start the engine in one operating mode within a certain period of time, it will be started in the other operating mode. This means that if there is a problem in the petrol system following natural gas refuelling, the vehicle will not start in petrol operation, but in natural gas operation. As soon as the Lambda regulator is active, it will attempt to switch to petrol operation.Actuating fuel system pressurisation pump G6 and fuel pressure regulating valve N276The electrical fuel system pressurisation pump is also permanently actuated during natural gas drive. The accumulated primary pressure prevents vapour lock in the mechanical high-pressure fuel pump and ensures adequate lubrication. The fuel pressure regulating valve should be actuated so that pressure on the high-pressure side stays at 100 bar. This ensures that the high-pressure injectors remain securely shut even if there is high pressure in the combustion chamber.AG.Cold start functionagen lksw Vo byProte cted byc o p yri gh t . C op yi13Engine management systemStarting strategy 1.4 l 81 kW TGI engineEngine start Coolant temperature less than -10 °C Starts in petrol mode Activating cold start function without previous natural gas fuelling Coolant temperature greater than or equal to -10 °C Starts in natural gas mode Starts in petrol mode Cold start function was not completed and will now be concludedSwitches over to natural gas mode Cold start function completed Starts in petrol mode Activating cold start functionSwitches over to natural gas mode Cold start function completed Starts in petrol mode Cold start function was not completed during the last engine operation, it will now be concludedwith previous natural gas refuelling or yet to be completed natural gas quality adaptionSwitches over to natural gas mode Cold start function completed and Lambda regulator active or minimum 648 sec. engine operation and min. 140 ml petrol flow rate*Switches over to natural gas modees, in part or in w l purpos hole ercia , is n m ot compe rm itte d* The high-pressure fuel pump and the high-pressure injectors are flushed with the petrol and are protected against soilingun leris tho u a ssCold start function was not completed Cold start function completed and Lambda regulator active or minimum 540 sec. engine operation k s l w o a V g . en AG AG does agen and ksw not l o V gu by ara ml petrol flow rate* min. 140 ednte eo ra cility ab y li an pt ceCold start function was completed Lambda regulator active and min. 140 ml petrol flow rate*rrectness of i t to the co nform spec a t i h re o n in wit thi sNatural gas refuellingNatural gas engines have very good lean-running capabilities, but relatively poor rich-running capabilities. For this reason, the air injection time is adjusted to the quality of the natural gas, H (rich) or L (lean), after each refuelling. If tank pressure sensor G400 detects that the tank pressure has risen by approx. 20% since the last engine operation, then it will assume the natural gas tanks have been refuelled and the petrol operation will start. It will switch over to natural gas operation after active Lambda regulation and 140 ml of petrol has been consumed. The natural gas quality adaption begins in the medium engine load and speed range. The opening times of the gas injection valves are hereby adjusted via Lambda regulation. The adaption takes 45 - 90 sec. when driving at a constant speed. When it has been completed, the engine usually starts in natural gas operation. Coolant temperaturer te o iva r rp fo g ndo c um enWhen regulating the natural gas pressure, the coolant prevents the gas pressure regulator from icing below -10 °C. Furthermore, the elastomer seals on the valve seats may stick together and no longer open below -10 °C.agen lksw Vo byAG.14ht rig py Co t.Prote cted by c o py rig ht . C op yiSensorsTank pressure sensor G400The fuel tank pressure sensor is screwed into the electronic gas pressure regulator. This sensor is connected to the high-pressure side via a transverse passage and measures the natural gas high pressure. Signal use This signal allows the engine control unit to recognise • the filling level of the natural gas fuel tanks • whether natural gas has been refuelled Implications of signal failure If the signal fails, then the natural gas operation will carry on. If the natural gas fuel tanks are almost full with natural gas when the failure occurs, then the vehicle will also start in the natural gas operation upon subsequent starts. If the failure occurs when the natural gas fuel tanks are not so full, then the vehicle will start in the petrol operation and conduct a natural gas quality adaption.s528_017 Tank pressure sensor G400Gas rail temperature and pressure sensor GX21The gas rail temperature and pressure sensor is screwed onto the gas distributor rail on the right-hand side of the car. It measures the pressure and temperature of the natural gas on the low-pressure side. Signal usees, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nAG. Volkswagen AG d agen oes ksw not l o V gu y b ara d nte ise r o eo h t u ra a c s sility ab y li an pt ceht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t. C op yiThe engine control unit requires the signal ... … from the pressure sensor • in order to decide whether the natural gas pressure is sufficient for natural gas operation • to regulate the natural gas pressure in the gas distributor rail at 5-9 bar … from the temperature sensor • for a precise calculation of the opening times for the gas injection valve, in order to inject the necessary quantity of natural gas as accurately as possible and • to initiate compensation measures, if the natural gas temperature in the low-pressure side falls below -40 °CGas rail temperature and pressure sensor GX21s528_018rrectness of i t to the co nform spec at i h re o n wit in t hisImplications of signal failureIf the pressure sensor signal fails, then the system immediately switches over to petrol operation. If the temperature sensor signal fails, then the natural gas temperature is measured by the engine control unit.do c um en15Engine management systemActuatorses, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nAG. Volkswagen AG d agen oes ksw not l o V gu y b ara d nte ise r o eo h t u ra a c s sility ab y li an pt ceTank shut-off valves 1 and 2 N361, N362Each natural gas fuel tank has a tank shut-off valve. It is screwed directly onto the fuel tank. Purposerrectness of i t to the co nform spec at i h re o n wit in t hiss528_010The valves are closed when there is no flow. For safety reasons, natural gas is prevented from flowing out of the fuel tanks whilst the engine is turned off. The other features of the fuel tank shut-off valves are: • • • manual tank shut-off a thermal valve for high temperatures restriction of the flow rateAG.Prote cted bydo c um enNatural gas fuel tank 1Implications of malfunctionIf one of the valves fails, the vehicle continues to drive in natural gas mode while there is sufficient natural gas.Design of the fuel tank shut-off valveFlow restrictorMechanical shut-off valveThermal valve Natural gas line connection16ht rig py Co t.agen lksw Vo byc o p yri gh t. C op yiTank shut-off valve 2 N362 Natural gas fuel tank 2Fuel tank shut-off valve 1 N361Ensure that the residual pressure in the natural gas fuel tank is less than 1 bar prior to disassembling the fuel tank shutoff valve. Observe the instructions in the service literature.Electromagnetic tank shut-off valves528_042Electromagnetic tank shut-offHow it works:es, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nAG. Volkswagen AG d agen oes ksw not l o V gu y b ara d nte ise r eo valve utho ra a c s sValve springility ab y li an pt ceValve disc Valve seatThe electromagnetic fuel tank shut-off valve has three switching states: Terminal 15 “OFF”rrectness of i t to the co nform spec at i h re o n wit in t hisThe valve spring closes the valve by pressing the valve disc against the valve seat when it is not energised. The flow of gas from the natural gas fuel tank is interrupted.From the natural gas fuel tankdo c um enElectromagnetic tank shut-off valveagen lksw Vo byAG.Terminal 15 “ON” and engine start in natural gas operation With Terminal 15 “on” the electromagnetic valves are jointly energised by the relay for gas shut-off valves J908. Due to the resulting magnetic field, the valve disc opposes the force of the valve spring to lift off the valve seat and opens the duct to the electronic gas pressure regulator. The fuel tanks are open and natural gas operation is possible.Electromagnetic valve From the natural gas fuel tankTo the electronic gas pressure regulator s528_061 Valve disc open Magnetic fieldNatural gas refuelling Whilst refuelling, the inflowing natural gas pushes the valve disc against the valve spring and off the valve seat with a pressure of up to approx. 260 bar dependant of the ambient temperature. The natural gas flows into the fuel tanks. If the pressure on both sides of the valve is equal, then the flow of natural gas will stop. The valve spring now pushes the valve back onto the valve seat and seals the fuel tanks.to the natural gas fuel tankfrom the gas filler neck s528_062ht rig py Co t.Prote cted byc o p yri gh t. C op yis528_06017Engine management systemn AG. Volkswagen AG do es n wage s k l ot g o yV ua b Flow restrictor ran ed s i tee r o h t or u ac a s s The flow restrictor is a safety valve and is located inility ab y li an pt cees, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ngthe connecting flange for each natural gas fuel tank. Purpose It prevents sudden, unregulated flows of gas from the natural gas tanks following damage to the natural gas line or because of a faulty gas pressure regulator.rrectness of i t to the co nf o r m spec atio h re n in witthi sd o cu m ens528_068Flow restrictor Connecting flange for the natural gas fuel tankHow it works:c o p yri gh t . C op yiLine system OKValve springValveUnder normal operating conditions, roughly the same natural gas pressure can be found either side of the flow restrictor. The valve spring holds the valve open.AG.Prote cted byA damaged natural gas line If a sudden drop in pressure occurs, for example, due to a ruptured natural gas line and the gas pressure is approx. 6.5 bar greater forward of the flow restrictor than it is behind it, then the valve will close due to the pressure differential. Due to a mandatory leakage function on the flow restrictor, the natural gas may only leak from the fuel tank at a heavily reduced rate of pressure. After ignition “off” or closure of the mechanical shut-off valve, pressure compensation will take place either side of the flow restrictor. Consequently, the flow restrictor will open again automatically.Valve seal seat Valve cone18ht rig py Co t.agen lksw Vo bys528_063s528_064 Natural gas pressure low Leakage bore Natural gas pressure highNatural gas is odourless. An odourant is added to the natural gas to be able to detect small leakages in natural gas systems.Mechanical shut-off valveThe mechanical shut-off valve allows you to close the natural gas fuel tank manually using a special hand wheel to make it gas-tight. For safety reasons, this is required during any work to the natural gas system.Mechanical shut-off valveFlow restrictorFor safety reasons, the channel to the thermal valve remains open even when the shut-off valve is closed.un leAG. Volkswagen AG d agen oes ksw not l o V s528_065 gu y b ara d nte ise r o Thermal valve Connecting eo h t u ra a piece bore c s sility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot comThermal valvepe rm itte drrectness of i t to the co nform spec a t i h re o n in wit thi sThe thermal valve is another component of the fuel tank shut-off valve. It prevents the natural gas fuel tanks from rupturing due to an excessive increase in pressure when the temperature is too high. How it works:External air ventNatural gasThe fusible plug closes the external air vent at normal ambient temperature.r te o iva r rp fo g ndo c um enIf the thermal valve is heated to a temperature above 110°C for a certain period of time, then the fusible plug will melt and the vent is opened. Now the natural gas from the natural gas fuel tank will leak at a controlled rate into the atmosphere.s528_067 Melted fusible plug Natural gas escaping into the ambient airAG.Prote cted byFusible plugNatural gasht rig py Co t.s528_066agen lksw Vo byc o p yri gh t. C op yi19Engine management systemElectronic gas pressure regulatorCoolant connections Low-pressure natural gasTank pressure sensor G400es, in part or in w l purpos hole ercia , is n m ot compe rm itte dun len AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed s i tee r o h t or u ac a ssility ab y li an pt cerrectness of i t to the co nform spec a t i h re o n in wit thi s2nd Reduction stage high-pressure valve for gas mode N372 High-pressure natural gass528_0361st Reduction stageMechanical excess pressure valveThe electronic gas pressure regulator comprises the following components:r te o iva r rp fo g nTank pressure sensor G400 This sensor is connected to the high-pressure side via a transverse passage and measures the high pressure natural gas.do c um enFirst and second reduction stages The first reduction stage reduces the natural gas pressure to 20 bar and the second stage reduces it to 5–9 bar. Mechanical excess pressure valve This valve is screwed into the low-pressure side of the gas pressure regulator and opens at approx. 16 bar. This prevents natural gas flowing into the low-pressure side at a high pressure and causing damage. Coolant connections Reducing the natural gas pressure cools down the natural gas on the low-pressure side. This in turn brings about low ambient and component temperatures, which can lead to icing up. To prevent this from happening, the gas pressure regulator is incorporated into the coolant system and is heated by the coolant.agen lksw Vo byAG.Prote cted by20ht rig py Co t.c o p yri gh t . C op yiRegulation of natural gas pressureRegulation of the natural gas pressure at 5–9 bar (absolute) has the following advantages compared with a fixed pressure of 7 bar (absolute) in the case of the first Touran/Caddy EcoFuel models with mechanical gas pressure regulator: Injection into the medium load/speed range occurs at a pressure of up to 5 bar. The low pressure allows the vehicle to be driven for longer in natural gas mode. This increases the range by up to 25 km. In the top load/speed range injection occurs at a pressure of up to 9 bar. This allows more gas to be AG. Volkswagen AG d agencycle with the maximum oes injected per working ksw not opening l o V gu y b gas injection valves. Only then is power ara of d time of the nte ise r o eo h t 81 kW and a torque of 200 Nm possible. u ra aun lesscility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot compe rm itte drrectness of i t to the co nform spec a t i h re o n in wit thi sSystem pressure (bar)Electronic gas pressure regulator, max. gas flow at full load 28 kg/hMechanical gas pressure regulator, max. gas flow at full load approx. 27 kg/hr te o iva r rp fo g ndo c um enGas mass flow (kg/h)s528_024agen lksw Vo byProte cted bySwitch-overs between operating modesThe selected operating mode is largely dependent on the natural gas pressure in the gas distributor rail. The engine will run in natural gas operation so long as the set pressure is achieved, otherwise it will switch over to petrol operation. Switch-over to petrol operation can occur with a fuel tank pressure showing 15-17 bar in the case of very dynamic driving styles and the high pressure associated with it. With sedate driving styles, the switch-over only occurs with a fuel tank pressure of 6-8 bar. In order to maximise driving range during natural gas operation, the engine will switch from petrol operation back to natural gas operation when the fuel tank pressure is above 8.5 bar. This means that if, for example, acceleration took place sharply with a fuel tank pressure of 15 bar and the engine switched over to petrol operation, then a delayed switch-over back to natural gas operation would take place with a more sedate driving style. The number of possible return switch-overs depends on the fuel tank pressure.ht rig py Co t.AG.c o p yri gh t. C op yi21Engine management systemReducing the natural gas pressure from high-pressure to low-pressureFirst reduction stage At the first reduction stage pressure is mechanically reduced from up to 200 bar to approx. 20 bar.s528_038 1st reduction stage High-pressure connection with filter elementThe natural gas pressure behind the hollow-bored piston is less than 20 bargen fuel tank The natural gas flows from the natural gas wa olks V by through the high-pressure connection and into the ed ris o h t first reduction stage. There it flows through the au ss the piston crown side. The hollow-bored piston on increasing pressure on the piston crown causes the piston to move against the spring force to the right.Piston crownPiston springHigh-pressure connectionAG. Volkswagen AG d oes not gu ara nte eo ra cility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot compe rm itte dun lerrectness of i t to the co nform spec a t i h re o n in wit thi ss528_025Hollow pistonIn-flow of natural gasThe natural gas pressure behind the hollow-bored piston is 20 bar When the pressure on the piston crown reaches approx. 20 bar, the hollow-bored piston lies against the seal. No more natural gas flows in and the pressure is reduced in the first reduction stage to approx. 20 bar. However, because natural gas is constantly being consumed during natural gas operation, the pressure on the piston crown drops back to under 20 bar straight away. The piston spring opens the hollowbored piston and the natural gas flows back in. The piston is invariably open when the pressure in the highpressure side drops below 20 bar.r te o iva r rp fo g nHigh-pressure connectiondo c um enNatural gas pressure 20 bar22ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t . C op yis528_026 SealSecond reduction stage In the second reduction stage the high-pressure valve for gas mode reduces the natural gas pressure from approx. 20 bar to 5-9 bar electronically. The pressure and temperature in the natural gas low-pressure side are measured by the gas rail temperature and pressure sensor GX21.s528_039AG. Volkswagen AG stage does agen 2nd reduction ksw not l o V gu y b ara Solenoid d e nte is r o eo th u ra a c s ses, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nThe natural gas pressure is approx. 20 bar in front of the high-pressure valve for gas mode. The first and second reduction stages are connected to each other via a duct. This now means that a pressure of approx. 20 bar is also applied to the closed high-pressure valve for gas mode.Duct from the 1st reduction stages528_028 Valve needle Ball valve Valve ball seatility ab y li an pt cerrectness of i t to the co nform spec at i h re o n wit in t hisRegulation of natural gas pressure at 5–9 barValve needleBall valveIn-flow of natural gasht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig ht . C op yiTo regulate the natural gas pressure to 5–9 bar, the high-pressure valve for natural gas operation is actuated by a pulse-width modulated signal (PWM signal) from the engine control unit. The valve needle is activated by the solenoid and the valve ball is lifted from its seat. The gas now flows until the necessary pressure is reached in the low-pressure natural gas system.Low-pressure side of the engines528_030do c um en23Engine management systempe rm itte des, in part or in w l purpos hole ercia , is n m ot comHigh-pressure valve for gas mode N372The high-pressure valve for gas mode is fitted directly onto the gas pressure regulator and performs the function of an electromagnetic shut-off valve. This is the second reduction stage and it controls the flow of natural gas to the engine. Purposeun len AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed s i tee r o h t or u ac a ssility ab y li an pt cerrectness of i t to the co nform spec a t i h re o n in wit thi sIf one of the high-pressure valves for gas mode fails, then the system switches over to petrol mode.24AG.Implications of malfunctionHigh-pressure valve for gas mode N372Electronic gas pressure regulatorht rig py Co t.During natural gas operation, the high-pressure valve for gas mode is actuated by a PWM signal from the engine control unit. The natural gas pressure can be reduced from 20 bar to 5–9 bar as necessary. The high-pressure valve for gas mode remains closed when not actuated by the engine control unit J263.r te o iva r rp fo g ndo c um enagen lksw Vo byProte cted byc o p yri gh t . C op yis528_023Gas injection valves 1 to 4 N366-N369The gas injection valves are inserted into the intake manifold ducts. They are activated by the engine control unit in natural gas mode. Purpose They have the task of injecting natural gas into the intake manifold. The opening times of the gas injection valves depend on: • • • • engine speed the engine load the natural gas quality and the pressure and temperature of the natural gas in the gas distributor rail.Gas distributor rail with gas injection valves N366–N369Implications of malfunction If one of the gas injection valves fails, the system switches over to petrol mode.es, in part or in w l purpos hole ercia , is n m ot compe rm itte dun leAG. Volkswagen AG d agen oes ksw not l Gas injection o gu yV b ara valve d e nte ris eo tho u ra a c s ss528_021ility ab y li an pt cerrectness of i t to the co nform spec a t i h re o n in wit thi sr te o iva r rp fo g ndo c um enht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig ht . C op yi25Engine management systemDash panel insertn AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed s i tee r o h t or u ac a ssility ab y li an pt ceThe following instruments and warning lamps are provided for natural gas mode and petrol mode in the dash panel insert. The natural gas gauge has replaced the coolant temperature gauge.rrectness of i t to the co nform spec at i h re o n wit in t hises, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g nMultifunction display (MFD)Total rangedo c um enNatural gas mode warning lamp K192Natural gas gauge G411Reserve fuel warning lamp K105Multifunction display (MFD)The multifunction indicator displays filling levels, range and consumption. Displays appear as messages and text. The driver can call up the following information or it will be displayed automatically: current consumption, average consumption, total range, individual range and natural gas quality. Further information appears when switching between operating modes, when an error is detected in the operating modes or when natural gas or petrol refuelling is necessary.Natural gas quality indicator Natural gas quality is displayed in 10% increments between 70 and 100%. After each refuelling, a natural gas quality adaption takes place, which uses the Lambda regulator to ascertain the methane content and thereby the natural gas quality. An instrument display of 100% indicates a methane content above 90%, an instrument display of 90% indicates a methane content over 80%. Because the methane content is not recorded, but only calculated, the quality indicator may vary from the actual methane content.26ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t . C op yis528_029Fuel gauge G1CNG Qualitys528_074Instruments and warning lights in dash panel insertNatural gas gauge G411 (analogue) The natural gas gauge shows the current natural gas supply in the natural gas tanks. Fuel gauge G1 (analogue) The fuel gauge shows the current petrol supply in the fuel tank. s528_069 Natural gas mode warning lamp K192 The green warning lamp for natural gas mode indicates that the vehicle is running in natural gas mode.AG. Volkswagen AG d agen oes ksw not l o gu yV b ara d e nte is r o eo h ut ra a c s sG411G1s528_070K192ility ab y li an pt ceurposes, in part or in wh ole, cial p is n mer m ot p o c erm or e t a itte v i r d pReserve fuel warning lamp K105 The yellow reserve fuel warning lamp is illuminated only when Fuel gauge G1 is in the reserve range. There are still around 5 l of petrol left once it goes into the reserve range.un les528_071G1, K105rrectne s s o f i t to the co n form spec atio h re n wit i n thi sd o c um ens528_073Multifunction display When the natural gas supply goes into reserve, an explanatory text will appear in the multifunction display consisting of a triangle with an exclamation mark and a chime is heard. The reserve zone commences at a fuel tank pressure of 15.2 bar.Multifunction display"Please refuel with CNG". Range: 25 kmr fo ngThe acronym CNG stand for compressed natural gas.ht rig py Co t.agen lksw Vo byAG.Prote cted by c o py rig h t . Co py is528_07727ServiceThe special features of gas vehicles swagnatural en AG n AG. Volk doe wageWho ispe rm itte dWork on the natural gas system may only be performed by persons with proven expert knowledge. Please pay special attention to the information provided in the service literature, diagnostic tester and on the vehicle itself.ility ab y li an pt cees, in part or in w l purpos hole ercia , is n m ot comWorking on the natural gas systemun leolks yV b ed allowed ris to work ho t au sson natural gass no t gu ara nte vehicles? eo ra cAlways carry out a pressure reduction in the natural gas high-pressure line before working on the natural gas system. Make sure to determine the residual pressure in the natural gas fuel tank prior to commencing work on a natural gas fuel tank or fuel tank shut-off valve. Only then can you be sure that the natural gas fuel tanks have been emptied except for a small residual gas quantity.rrectness of i t to the co nform spec a t i h re o n in wit thi sWhen refuellingr te o iva r rp fo g nThe natural gas fuel tanks and the natural gas itself heat up during refuelling. If you then park the vehicle, both will cool down and the pressure in the natural gas tanks will decrease. As a result, the natural gas gauge may show a lower filling level than before the vehicle was parked.do c um enht rig py Co t.The pressure in the natural gas tanks should be 200 bar maximum when the temperature of the natural gas tanks and the natural gas is 15°C. Since the pressure in the natural gas tanks varies depending on the ambient temperature and the heat created due to compression during refuelling, a higher pressure may be applied for filling based on a calculation model. After cooling to 15°C, this pressure should be 200 bar. The natural gas mass filled in kg, not the filling pressure, is important for the driver.After refuelling or an ambient temperature below -10°CThe engine is always started in petrol mode after refuelling or in the case of low ambient temperature. This leads to the petrol being gradually consumed even though the natural gas supply itself has not been completely used up.Natural gas qualityThere are two natural gas quality levels, natural gas H and natural gas L. Natural gas H has a higher methane content and thus a higher calorific value, which means a lower fuel consumption. However, there are also differences within the quality levels, which effect the fuel consumption and the range.Information on the natural gas fuel tanksSome information is stamped onto the natural gas fuel tanks, for example the dead weight in kg, the water filling volume in litres and the life span of the natural gas fuel tank.28agen lksw Vo byAG.Prote cted by c o py rig h t . Co py iAfter refuellingSpecial toolsDescription Tool UsageV.A.G 1274 B/12 Residual natural gas pressure test adapter (thread width 6 mm)AG. Volkswagen AG d s528_045 agen oes ksw not l o V g y ua b ran ed tee V.A.G 1331/8 horis t or u ac a sspe rm itte dFor connecting the natural gas fuel tank to cooling system tester V.A.G. 1274 B when checking for residual pressureFlared ring spanner tool insert SW 14es, in part or in w l purpos hole ercia , is n m ot comThe union nuts on the high-pressure lines can be tightened with a prescribed torque by using torque wrench V.A.G. 1331 together with the flared ring spanner tool insert.ility ab y li an pt ceun les528_046rrectness of i t to the co nform spec a t i h re o n in wit thi sT10521 Insert tool s528_047For fastening and unfastening nuts onto the fuel tank shut-off valveT10522 Insert tool s528_048For fastening and unfastening plugs onto the fuel tank shut-off valveT10523r te o iva r rp fo g ns528_049 For lowering the natural gas fuel tanksGearbox support s528_050 VAS 6131/14-1 Pads s528_051 VAS 6901 Battery lamp s528_052 The explosion-proof LED portable lamp to be used during maintenance and inspection The natural gas fuel tanks rest upon polystyrene pads. You can use a knife to cut the pads to fit the shape of the fuel tanks.AG.T40173/1ht rig py Co t.agen lksw Vo byProte cted by c o py rig h t . Co py iTensioning strapFor securing one of the natural gas fuel tanks on gearbox support T40173 against falling down or twistingdo c um en29Test your knowledgeWhich answers are correct?One or several of the given answers may be correct. 1. How can it be ascertained in the workshop whether the natural gas fuel tank is “empty”?does ag a) When there is no more gas flowing out of theotank can be assumed that the noit lksw whilst it is being drained, t gu yV b ara d fuel tank is empty. e nt ris❒ ❒ ❒olkswagen AG en AG. Vc) The “determine residual pressure in the natural gas fuel tank” test reliably ascertains, whether or not the fuel tank is empty.rrectne s s o f i t to the co n form spec atio h re n wit i n thi sd o c um en2.What should you look out for when assembling the securing straps onto the spring assembly? a) There should be three spring assemblies with the same number of spring washers. b) The correct arrangement of the spring assemblies must be observed. c) The spring assembly is adjusted under specific conditions to a preset measurement.❒ ❒ ❒3.r fo ngWhich statement or statements are true, when switching from natural gas operation to petrol operation? a) If the natural gas fuel system was depleted to the extent that the engine switched from natural gas operation to petrol operation, then the natural gas fuel tanks are definitely empty. b) If the natural gas fuel system was depleted to the extent that the engine switched from natural gas operation to petrol operation, then there is still a residual amount of natural gas in the fuel tanks. c) If the natural gas fuel system was depleted to the extent that the engine switched from natural gas operation to petrol operation, then the natural gas fuel tanks could yet still be full and it was an error in the natural gas system that caused the engine to switch over to petrol operation.agen lksw Vo byAG.ht rig py Co t.Prote cted by c o py rig ht . C op yi❒ ❒ ❒4.What should you look out for with the Golf/Golf Estate TGI when tightening the union nuts onto the high-pressure lines? a) The nuts are tightened hand-tight with a 90° turn angle. b) The nuts are tightened to a specific torque. c) The nuts are only tightened hand-tight.❒ ❒ ❒30urposes, in part or in wh ole, cial p is n mer m ot p o c erm or e t a itte v i r d pun leb) The fuel tank is weighed and compared against the weight stamped onto the fuel tank.tho au s see or acility ab y li an pt ce5.The tank shut-off valves … a) … can be closed mechanically with a hand wheel. b) … are closed when de-energised and are opened and kept open with ignition “on” and engine start in natural gas operation electromagnetically. c) … are open when de-energised and are closed electromagnetically with ignition “on”.❒ ❒ ❒6.The electronic gas pressure regulator … a) … regulates natural gas pressure in two reduction stages to between 5 and 9 bar as necessary. b) … is connected to the cooling system to prevent the reduction stages from freezing. c) … regulates the natural gas pressure to 12 bar electronically.n AG. Volkswagen AG do es n wage s k l ot g o yV ua b ran ed of the following should be observed when installing/removing s i tee r o h t or u ac a ssility ab y li an pt ce❒ ❒ ❒7.Whichthe natural gas fuel tanks?❒ ❒es, in part or in w l purpos hole ercia , is n m ot p om c r erm o e t a itte riv du p or nl f e g n❒a) The high-pressure lines must be laid in a way that the nuts may be manually tightened as far as they will go. Only afterwards are the connections to be tightened with a constant torque. b) Mark the installation position of the securing strap pads on the natural gas fuel tank and measure the position of the securing straps prior to removing the fuel tank. c) Take extreme care to ensure that the natural gas fuel tank is not scratched whilst being installed/removed.rrectness of i t to the co nform spec at i h re o n wit in t hisdo c um enSolution: 1.) c) 2.) a); b); c) 3.) b); c) 4.) b) 5.) a); b) 6.) a); b) 7.) a); b); c)ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t . C op yi31528AG. Volkswagen AG d agen oes ksw not l o V gu y b ara d nte ise r o eo h t u ra a c s sility ab y li an pt cees, in part or in w l purpos hole ercia , is n m m ot p o c erm or e t a itte iv r du rp o nl f e ngrrectness of i t to the co nf o r m spec atio h re n in witthi sd o cu m en© VOLKSWAGEN AG, Wolfsburg All rights and rights to make technical alterations reserved. 000.2812.85.20 Technical status 12/2013 Volkswagen AG After Sales Qualification Service Training VSQ/2 Brieffach 1995 D-38436 Wolfsburg❀ This paper was manufactured from pulp that was bleached without the use of chlorine.ht rig py Co t.agen lksw Vo byAG.Prote cted byc o p yri gh t. C op yi