Volkswagen Golf/Jetta/Cabriole 1990-1999

Fuel Pump

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DESCRIPTION



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.

1990-92 Cabriolet, Golf, Jetta and Fox
Transfer Pump
  1. Remove the rear seat and the access cover.
  2.  
  3. Disconnect the wiring and hoses and unscrew the lock ring.
  4.  
  5. Carefully lift out the pump and gauge sending unit assembly.
  6.  
  7. When installing the assembly, use a new seal.
  8.  

Main Pump
  1. Disconnect the negative battery cable.
  2.  
  3. Relieve the fuel system pressure.
  4.  
  5. Raise and safely support the rear or right side of the vehicle on jack stands.
  6.  
  7. Disconnect the wiring from the pump. Clean any dirt away from the fuel line fitting.
  8.  
  9. Use locking pliers to pinch off the fuel line from the transfer pump to the main pump. If the fuel line is metal, remove the rear seat and access panel and disconnect the line at the transfer pump.
  10.  
  11. Place a pan under the pump and disconnect the fuel line fitting from the pump.
  12.  
  13. Remove the retaining ring screws and slide the pump out of the reservoir.
  14.  

To install:

  1. Moisten the pump O-ring with a little fuel and slide it into the reservoir. Install the retaining ring screws.
  2.  
  3. When connecting the fittings, use new copper washers and tighten the fittings to 15 ft. lbs. (20 Nm).
  4.  

1993-99 Cabrio, Golf, and Jetta
  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.  

TESTING



Fuel Pump Test

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.  

Fuel Pump Electrical Circuit
  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.  

 
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