Volkswagen Cars 2000-05

Fuel Pump

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General Information



On a Digifant fuel system, the fuel pump is mounted in a reservoir under the rear of the vehicle. The fuel filter is also in this area. The reservoir holds one liter of fuel and is supplied by a small transfer pump in the tank. The transfer pump can be replaced separately even though they are installed and removed as a unit.

The Motronic system uses two fuel pumps. The first is a small transfer pump to get the fuel out of the tank and the second boosts the fuel pressure to the necessary amount. The transfer pump is located inside the tank and the main pressure pump can be found under the vehicle. This transfer pump is located under the rear seat and is part of the fuel gauge sending unit. The main fuel pump can be found in the reservoir in front of the rear axle beam. There is a check valve inside this pump to maintain pressure in the lines, especially on hot days, to avoid vapor lock. The fuel filter is mounted to the side of the reservoir. This filter has no specified replacement interval and should be good for the entire service life of the vehicle. Whenever the ignition key is in the on position, the pump should run for at least two (2) seconds to pressurize the fuel lines. If the Engine Control Unit (ECM) does not see a signal from the Hall Effect sensor in the distributor it will shut the pump off. If a Hall Effect signal is present, the pump will continue to run as long as a signal is detected. It is this Hall Effect signal that signals the ECM that the engine is rotating therefore indicating that fuel is needed. The pump is operated via a relay that is controlled by the ECM. This relay is located in the vehicles fuse panel. The main contacts of the relay can be jumped to run the pump during testing.

Removal & Installation




NOTE
On CIS systems the main fuel pump is located under the vehicle in front of the rear axle or in front of the tank on the right side.

  1. Remove the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Relieve the fuel system pressure.
  6.  
  7. Remove the rear seat and the access cover.
  8.  
  9. Disconnect the wiring and hoses.
  10.  
  11. Remove the fuel lines from the pump.
  12.  
  13. On 1993-99 Golf, Jetta and Cabrio vehicles, unscrew the fuel pump retaining ring.
  14.  
  15. On all other models, remove the mounting bolts and the fuel pump.
  16.  
  17. Carefully lift out the pump and gauge sending unit assembly.
  18.  
  19. Empty the fuel pump into an approved container.
  20.  

To install:

  1. Installation is the reverse of removal. Be sure to use new sealing rings and/or gaskets.
  2.  


CAUTION
Observe all safety precautions while performing the procedure.


CAUTION
Determine the correct radio anti-theft coding before disconnecting the battery.

  1. With the ignition switch off, disconnect the battery negative cable.
  2.  
  3. Remove the fuel pump access cover in luggage compartment floor
  4.  



Click image to see an enlarged view

Fig. Fuel pump access cover removal

  1. Disconnect the harness connector, fuel supply and return hose from the flange.
  2.  
  3. Remove the ring nut with spanner wrench.
  4.  
  5. Remove the flange and sealing ring from the fuel tank opening.
  6.  
  7. Loosen the fuel pump module from bayonet connection by turning it to the left and removing it from the tank opening.
  8.  


CAUTION
If the fuel pump module is still filled with fuel, empty before installation.

To install:

  1. Installation is in the reverse order of removal procedure. Note the following during installation:
  2.  
    1. When installing the fuel pump module, make certain the fuel sensor arm is not bent.
    2.  
    3. Lubricate the flange seal with fuel before installing.
    4.  
    5. Ensure the proper installation position of the fuel pump module flange and attaching parts, as shown.
    6.  
    7. When the fuel pump module is correctly installed, the fuel gauge sender points to the direction of travel 'A', as shown.
    8.  




Click image to see an enlarged view

Fig. Positioning the fuel pump module

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. The main fuel pump is located under the vehicle in front of the rear axle or in front of the tank on the right side. Disconnect the negative battery cable.
  4.  
  5. Remove or disconnect:

    Electrical connector.
     
    Fuel system pressure.
     
    Mounting bolts
     
    Fuel pump.
     

  6.  
  7. Installation is the reverse of removal. Be sure to use new sealing rings and/or gaskets.
  8.  

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Relieve the fuel system pressure.
  4.  
  5. Disconnect the negative battery cable.
  6.  
  7. Remove or disconnect:

    Cover under rear seat
     
    Electrical connector
     
    Fuel supply and return lines
     

  8.  
  9. Using spanner tool 3217, remove the fuel pump flange nut.
  10.  
  11. Remove the fuel pump unit and seal.
  12.  
  13. Installation is the reverse of removal. Be sure to use new sealing rings and/or gaskets. Tighten the fuel pump flange nut to 55 ft. lbs. (75 Nm) and make sure the markings on the flange nut match the marking on the fuel tank.
  14.  

Testing



The fuel pump runs only when the engine is running or is being started. Therefore the fuel pump relay must be jumped. This will enable the pump to run constantly so that an accurate test can be performed.


NOTE
If the pump does not run, make sure it has a good ground and is getting the necessary 12 volts from the battery.

  1. Remove the fuel pump relay from the fuse box.
  2.  
  3. With the ignition off, bridge the number 87 terminal of the relay to the positive post of the battery using a jumper wire.
  4.  
  5. If the pump runs only when the jumper wire is attached, check the wiring going to the fuel pump.
  6.  
  7. Once you are sure that the wiring to the pump is not at fault, the Electronic Control Module (ECM) may be bad.
  8.  

See procedure under 'Electric Fuel Pump' heading

Circuit Inspection
  1. To begin testing the fuel pump electrical circuit first check that the battery is at a full state of charge.
  2.  


NOTE
Do not forget to check the condition of the fuse in the box, if it is blown the fuel pump will not receive the necessary electricity it needs to operate correctly.

  1. Remove the access panel from the fuel pump.
  2.  
  3. Turn the key to the on position and have a helper listen for the pump to begin running. If the system is operating correctly, the pump should run for a short period and then shut off. If the pump does not run, continue on to the following steps.
  4.  
  5. Remove the fuel pump relay and operate the pump as shown in the fuel pump test. If the pump runs after performing the fuel pump test, proceed to the next diagnostic step in this procedure.
  6.  
  7. Pull the jumper cable from the relay and then while the ignition switch is off, connect an Digital Volt Ohm Meter (DVOM) to the #3 terminal and the # 85 terminal on the relay. Turn the key on, there should be a momentary ground signal. If a ground is present at terminal # 85, the relay is faulty. If no ground is detected, check the wiring at the engine control module. If no faults can be found in the wiring the Electronic Control Unit (ECU) is the cause.
  8.  

Diagnosis & Testing
  1. To begin testing the fuel pump electrical circuit, first check that the battery is at a full state of charge.
  2.  


NOTE
Do NOT forget to check the condition of the fuse in the fuse box. If it is blown, the fuel pump will not receive the necessary electricity to operate.

  1. Remove the access panel from the fuel pump.
  2.  
  3. Turn the ignition key to the ON position and have a helper listen for the pump to begin running. If the system is operating correctly, the pump should run for a short period and then shut off. If the pump does not run, continue on to the following steps.
  4.  
  5. Remove the fuel pump relay and operate the pump using a remote by-pass switch. If the pump runs after performing this test, proceed to the next diagnostic step in this procedure.
  6.  
  7. Install the fuel pump relay again.
  8.  
  9. Check for proper activation of the fuel pump relay, using an appropriate circuit tester.
  10.  
  11. If the fuel pump does not run when the relay is by-passed follow the following procedures:
  12.  
    1. Remove luggage compartment floor cover.
    2.  
    3. Disconnect the fuel pump wiring connector.
    4.  
    5. Remove the fuel pump relay and install a remote starter, VAG 1348/3A, with adapter wire, to connector and battery plus (+) terminal.
    6.  

  13. Connect an LED tester, VAG 1527B (or equivalent), to outer terminal of connector, using jumper wires from test kit.
  14.  

If LED does not light up, check the circuit wiring for faults. Repair as necessary.

If LED lights up, loosen flange nut with special spanner wrench, and then check the wiring and connections between the flange and fuel pump assembly.



If no open circuit is found, the fuel pump is defective and needs to be replaced.
 

Fuel Transfer Pump

Testing of the transfer pump is done by measuring the delivery rate of the pump. To accomplish this test you will need a measuring container and fuel hose (max. 14 in)

  1. Remove the access cover to the transfer pump.
  2.  
  3. Remove the fuel filler cap
  4.  
  5. Bypass the fuel pump relay to operate the pump. An assistant should be available to assist with this test.
  6.  
  7. Make a jumper wire at least 14 in long of 14-gauge wire. For safety, include an in-line fuse holder (20 amp).
  8.  
  9. Avoid damage to the relay panel sockets. The ends of the jumper should be flat-blade connectors that are the same size as the terminals on the relay.
  10.  



Click image to see an enlarged view

Fig. Passat fuse/relay panel. Fuel pumps are powered via fuse No. 18 and relay No. 12.


NOTE
The fuel pump should begin to operate. If not, test for proper current to the fuel transfer pump connector with a test light. If current is available and the pump will not start pump, the pump is defective. If pump begins to operate and fuel begins to flow, continue with the delivery rate test.

  1. With container and hose measure the fuel volume.
  2.  
    1. Length of test. 10 seconds
    2.  
    3. Minimum fuel quantity 10.1 fl. Oz. (300 cc)
    4.  



NOTE
If the pump fails the above quantity test, before replacement, remove the pump and verify that the strainer/filter is clean. If the strainer/filter is dirty, clean and retest.

  1. Reinstall components disconnected/removed for testing.
  2.  

Main Fuel Pump

Testing of the main fuel pump is done by measuring the delivery rate of the pump. To accomplish this test you will need a measuring container and fuel hose (max. 14 in).


NOTE
On CIS systems the main fuel pump is located under the vehicle in front of the rear axle or in front of the tank on the right side.

  1. Disconnect the fuel return line at the connection in the engine compartment near the right front suspension strut tower.
  2.  
  3. Connect a voltmeter to measure the actual voltage at the fuel pump connector.
  4.  
  5. Bypass the fuel pump relay to operate the pump.
  6.  
  7. With container and hose measure the fuel volume. Run the test for 30 seconds and measure the fuel volume.
  8.  


NOTE
The minimum fuel delivery depends on voltage supplied to the pump. See chart for minimum fuel quantity vs. voltage.



Click image to see an enlarged view

Fig. Fuel pump voltage vs. pump flow chart


NOTE
For all other VW Passat 1994-2000 and Audi A4 1996-2000, see procedures under 'Electric Fuel Pump' heading.

 
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