Fuel Injectors, Checking for Leaks and Injection Quantity

Fuel Injectors, Checking for Leaks and Injection Quantity






Special tools, testers and auxiliary items required

• Remote control connection (V.A.G 1348/3A)

• Adapter lead (V.A.G 1348/3-2)

• Injector quantity testing device (V.A.G 1602)

• Connector test kit (V.A.G 1594 C)

• Test instrument adapter/DSO (5-pin) (VAS 5565)

Perform the following:

Checking for leaks

• Fuel pressure must be OK, checking => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking.

- Remove the fuel rail - 3 - with the fuel injectors installed - 1 -(refer to => [ Fuel Rail and Fuel Injectors, Removing and Installing ] Fuel Rail and Fuel Injectors, Removing and Installing) and lay it on a clean cloth.






Do not disconnect battery and do not disconnect fuel supply line at quick acting coupling or at fuel rail.

• The connectors must be disconnected from the fuel injectors.

- Remove the bench seat. Refer to; Seat Bench, Removing and Installing.

- Remove the cover - 1 - from the fuel delivery unit. Arrow - 2 - points in direction of travel.






- Make sure the connector - arrow - is secure. Pull on the connector without pressing the catch. If the connector was not connected correctly, it could cause a fault.






- Pull on the connector.

- Check the contacts on the connector and on the fuel delivery unit for damage.

- Connect the test instrument adapter/DSO (5-pin) (VAS 5565) to the connector and to the fuel delivery unit.






- Connect the VAG 1348 remote control (V.A.G 1348/3A) to the test instrument adapter/DSO (5-pin) (VAS 5565) and to the positive (+) battery terminal.

- Operate Remote Control (V.A.G 1348/3A).

• This work step allows the fuel pump to run when the engine is not running.

- Check injectors for leaks (visual inspection).

• Only 1 to 2 drops per minute may emit from each valve when fuel pump is running.

If the fuel loss is greater:

- Disconnect connection to battery plus (+) and replace leaking fuel injector => [ Fuel Injectors, Removing and Installing ] Fuel Injectors, Removing and Installing.

Injection Quantity, Checking

• Fuel pressure must be OK, checking => [ Fuel Pressure Regulator and Residual Pressure, Checking ] Fuel Pressure Regulator and Residual Pressure, Checking.

• Fuel rail removed.

• Fuel injectors installed in fuel rail and fuel line connected.

• Fuel Pump (FP) runs (connected to battery with adapter cables).

- Insert fuel injector to be tested into measuring container of fuel injection quantity tester (V.A.G 1602).

- Connect one terminal of the fuel injector being tested to the engine ground using the adapter cables taken from the connector test kit (V.A.G 1594 C).






- Connect second terminal of fuel injector with adapter cable to remote control connection (V.A.G 1348/3 A) using adapter cable (V.A.G 1348/3-2).

- Connect alligator clip to B+.

- Operate remote control (V.A.G 1348/3A) for 30 seconds.

- Repeat the test on the other fuel injectors. Use new graduated measuring glasses for this.

- After all fuel injectors have been activated, place graduated measuring glasses on a level surface and compare quantity of injected fuel.

• Specified value: 85 to 105 ml per valve

While checking the injection quantity, the spray pattern should also be checked. Spray pattern must be the same for all fuel injectors.

If the measured value of one or more fuel injectors is below or above the indicated specified value:

- Replace faulty fuel injector => [ Fuel Injectors, Removing and Installing ] Fuel Injectors, Removing and Installing.