Volkswagen Front Wheel Drive 1974-1989 Repair Guide

Fuel Injectors

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Relieve the pressure from the system.
  4.  
  5. Using a small prytool, pry the injectors up out of the head. A spray lubricant can help release stuck injectors.
  6.  



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Fig. Fig. 1: A small prytool can be used to remove the injectors

  1. Hold the fuel line fitting with a line wrench and unscrew the injector.
  2.  
  3. Discard the old rubber rings.
  4.  



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Fig. Fig. 2: A seal pick is helpful for removing the small O-ring



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Fig. Fig. 3: The large O-ring should also be replaced

To install:
  1. Lightly lubricate the rubber rings.
  2.  
  3. Screw the injector onto the fuel line fitting. Tighten until snug.
  4.  
  5. Push the injectors straight into the head.
  6.  
  7. Connect the battery cable.
  8.  

TESTING



See Figures 4, 5 and 6

The injectors in all CIS systems are purely mechanical and open at a pre-determined pressure. All injectors are open when the engine is running, injecting fuel to the intake ports continuously. The spray pattern is critical to good atomization of the fuel, which will affect power and emissions. The injectors can be tested for spray pattern and leakage with tool US 4480 or equivalent. This is a set of clear, graduated cylinders that allow viewing the spray pattern and measuring the fuel flow.


CAUTION
The following procedure will produce fuel vapors. Make sure there is proper ventilation and take the appropriate fire safety precautions. Fuel will be sprayed from the injectors at high pressure. Do not point the injector at anything except the test tube.

  1. Remove the injectors by prying them out of the head. Inspect the injectors for signs of leakage. They should not be wet.
  2.  
  3. Carefully route the fuel lines so the injectors can be inserted into the tubes.
  4.  
  5. Locate and remove the fuel pump relay on the main fuse panel. Install tool US 4480/3 in the fuel pump relay socket. This is essentially a jumper wire with a switch used to turn on the fuel pump. The fuel pump will run any time the switch is ON.
  6.  
  7. Remove the airflow sensor boot and insert a 0.020-0.040 inch (0.50-1.0mm) feeler gauge between the airflow sensor plate and the housing so the plate is slightly lifted.
  8.  
  9. Operate the fuel pump and observe the spray pattern. It should be a narrow conical pattern, even all the way around. Move the sensor plate up higher to see how the pattern changes. Any irregularity in the pattern indicates a partially clogged injector. Raising the sensor plate all the way may clear it.
  10.  



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Fig. Fig. 4: Cross-sectional view of the fuel injector



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Fig. Fig. 5: Tubes used to measure injector flow quantity



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Fig. Fig. 6: Fuel injector spray patterns

  1. After one tube has about 20cc, stop the fuel pump and observe the injectors. Note the quantity of fuel in each tube; they should all be within 2cc of each other.
  2.  
  3. Repeat the test with the sensor plate all the way up to flow about 80cc of fuel. The flows should all be within 8cc.
  4.  
  5. If an injector flows high or low, move it to another line and flow test them again. If the incorrect flow follows the injector, the injector is faulty. If the incorrect flow stays with the same fuel line, the line or the fuel distributor is faulty.
  6.  
  7. To leak test the injectors, remove the feeler gauge so the sensor plate is resting on its stop and run the fuel pump. There should be no fuel dripping from any injector. Any injector with a bad spray pattern, leak or incorrect flow quantity must be replaced.
  8.  

 
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