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20Fuel Supply System
Edition 08.96
Safety precautions when carrying out work on fuel supply system
Important!
Fuel system is pressurised! Place cleaning ragsaround the connection point before opening the
system. Then, release pressure by carefullyloosening the connection point.
Pay attention to the following points when re- moving and installing the fuel gauge sender or the fuel pump (fuel delivery unit) from the fuel tank: Fuel tank should be not more than
2/3 full.
The extraction hose of an exhaust extraction system should be placed close to the assembly opening of the fuel tank and the extraction system switched on before commencing work in order to extract the fuel vapours which are released. If no exhaust extraction system is available, it is possible to use a radial fan with a delivery volume of more than 15 m
3/h (motor not
positioned in the air flow).
Avoid skin contact with fuel! Wear fuel- resistant gloves!
Rules for cleanliness
Pay careful attention to the following „5 rules“for cleanliness when carrying out work on the fuel supply/fuel injection system: Thoroughly clean connection points and the surrounding area before disconnecting.
Place removed parts down on a clean
surface and cover over. Do not use fluffing cloths!
Carefully cover over or seal opened com- ponents if repairs are not carried out imme-
diately.
Install only clean parts: Do not remove replacement parts from their wrapping until just before installing. Do not use parts which have been stored unwrapped (e.g. in tool boxes etc.).
If the system is open:
Avoid working with compressed air, if possible.
Avoid moving the vehicle, if possible.
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Edition 08.96
Testing fuel pump
Special tools, testers and aids required
Hand-held multimeter (e.g. V.A.G 1526)
Wrench for union nut (e.g. MP 1-227)
Adapter cable set (e.g. V.A.G 1594)
Current flow diagram
Test conditions
Holding pressure o.k.; testing:
1.8 ltr./92 kW Engine, Motronic Fuel Injection and Ignition System; Repair Group 24;
Testing fuel pressure regulator and holding pressure
Battery voltage at least 12 V
Fuse 28 o.k.
Fuse filter o.k.
Test procedure
- Switch on ignition. The fuel pump should be heard to operate. (A second mechanic may be required if there is a high level of surrounding noise) If the fuel pump does not run:
- Switch off ignition.
- Connect remote control V.A.G 1348/3A with adapter cable V.A.G 1348/3-2 page 20-8.
- Operate remote control.If the fuel pump runs:
Test fuel pump relay: 1.8 ltr./92 kW Engine, Motronic Fuel Injection and Ignition System; Repair Group 24; Servicing Motronic fuel injection system; testing fuel pump relay and actuation
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20Fuel Supply System
Edition 08.96
If the fuel pump does not run:
- Unbolt cover (below the rear seat).
- Release 4-pin connector form the flange at
the fuel tank and unplug.
- Connect hand-held multimeter (e.g. V.A.G
1526) with auxiliary cables (e.g. from V.A.G
1594) to the outer contacts of the connector.
- Operate remote control. Specification: about battery voltage
If the specification is not achieved:
- Determine open circuit in the wiring on the basis of the current flow diagram and rectify:
⇒ Current Flow Diagrams, Electrical Fault Finding and Fitting Locations binder
If the specification is achieved:
- Use MP 1-227 to unscrew union nut.
- Check whether the electric cables between flange and fuel pump are connected and test
for continuity.
If no open circuit in the wiring can be found:
Fuel pump faulty.
- Replace fuel delivery unit ⇒ page 20-5.
Testing delivery of the fuel pump
Special tools, testers and aids required♦ Adapter V.A.G 1318/17
♦ Measuring vessel
Test conditions
Battery voltage at least 12 V
Voltage supply o.k.
Fuel filter o.k.
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Edition 08.96
Test procedure
- Switch off ignition.
- Connect remote control V.A.G 1348/3A with
adapter cable V.A.G 1348/3-2 ⇒ page 20-8.
- Remove cap from the fuel filler neck.
Important! Fuel system is pressurised! Place cleaning ragsaround the connection point before opening the
system. Then, release pressure by carefullyloosening the connection point.
- Disconnect fuel return flow pipe -2- (press
release buttons).
- Connect auxiliary hose to adapter V.A.G 1318/17 and fit onto the fuel return flow pipe of the engine and hold in a measuring vessel.
- Operate remote control for 15 seconds (press button and hold).
- Compare quantity of fuel supplied with spe-
cification.
*)Minimum delivery cm3/15 s
**)Voltage at fuel pump when engine switched
off and pump running (about 2 V less than battery voltage).
