Each individual injector can be easily quick-checked to evaluate its spray pattern and to check for leakage. A more involved test compares the injection quantity from all four injectors to see that both the fuel distributor and the injectors are supplying equal amounts of fuel to each cylinder. Finally, a special injector tester can be used to measure opening pressure, clean the injector nozzles, or check and flush new injectors prior to installation.
If the quick-check suggests that more testing is necessary and the necessary measuring or testing equipment is not available, we suggest having the injectors tested by an authorized Volkswagen dealer or other qualified and properly equipped repair shop.
To quick-check injectors:
Remove the injectors as described above, leaving the fuel lines connected. Position the injectors so that their spray patterns will be visible and the discharged fuel can be caught in a fuel-resistant container.
Disconnect the large rubber air duct from the top of the air flow sensor.
Connect a remote switch or a fused jumper wire to bypass the fuel pump relay and run the fuel pump, as described in 4.1 Fuses and Relays.
Slowly lift the air flow sensor plate, using a magnetic tool as shown in Fig. 4-29, and observe the spray pattern of each injector. They should discharge a fine mist of fuel in a uniform, cone-shaped pattern.
Release the sensor plate to stop the flow of fuel. Hold each injector in a horizontal position and make sure that it does not drip fuel.
Magnetic tool (1) being used to lift air flow sensor plate (2) for quick-check of fuel injectors.
Fuel will be discharged from all four injectors during this check. Keep the test time short and discharge as little fuel as possible. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.
Disconnect the remote switch or jumper wire to stop the fuel pump.
An injector with an irregular spray pattern, or one that drips fuel when the sensor plate is at rest, should be replaced.