Fuel Injectors, Checking Injection Quantity, Leaks and Spray Pattern
Fuel Injectors, Checking Injection Quantity, Leaks and Spray Pattern
Test condition
• Fuel pressure OK
Removing fuel rail
- Remove engine compartment cover.
- Remove connecting pipe between air cleaner housing and throttle valve body.
- Disconnect vacuum hose from fuel pressure regulator.
- Disconnect connectors from injectors and remove cable ties as necessary.
- Remove fuel rail from intake manifold and lift off with injectors.
Checking injectors for leaks
- Place injector to be tested in a measuring glass from injection quantity tester (V.A.G 1602).
- Connect test box (V.A.G 1598/31) at wiring harness to engine control module. Engine control module is not to be connected. Refer to => [ Wiring and Component Check with Test Box Adapter Cable VAG 1598/31 ] Wiring and Component Check With Test Box Adapter Cable VAG 1598/31.
- Bridge contacts 1 and 65 on test box using test leads from adapter set (V.A.G 1594 A) (this creates a Ground connection to one side of fuel pump relay coil).
- Switch ignition on.
• Once the ignition has been switched on, the fuel pump runs continuously even if the engine is not running for the following reason: with the ignition switched on, the fuel pump relay receives its positive voltage supply via the engine electrics. The Ground voltage supply for the fuel pump relay comes via the cable bridge in the test box.
- Check injectors for leaks (visual check). With fuel pump running, only 1 to 2 drops per minute per injector may emerge.
- If fuel loss is greater than this, switch off fuel pump (switch ignition off) and replace faulty injector.
Checking injection quantity
- Place injector which is to be tested into measuring glass of injection quantity tester (V.A.G 1602).
- Connect one of injector contacts to engine Ground (GND) using a test cable and alligator clip from adapter set (V.A.G 1594 A).
- Connect second contact of injector with remote control V.A.G 1348/3A, adapter lead VAG 1348/3-2 and auxiliary cable to positive.
- Use leads from adapter set (V.A.G 1594 A) to bridge contacts 1 and 65 at test box.
- Switch ignition on.
• Fuel pump should run
- Activate remote control V.A.G 1348/3A for 30 seconds.
- Perform measurements on all injectors.
- Once all four injectors have been actuated, place measuring glasses on a level surface.
Specification for each injector: 105 to 125 ml
If specified result is not attained for all injectors:
- Check fuel pressure. Refer to => [ Fuel Pressure Regulator and Holding Pressure, Checking ] Fuel Pressure Regulator and Holding Pressure, Checking.
If specified results are not attained for one injector:
- Replace relevant injector.
• When checking the injection quantity, also check the spray pattern. The spray pattern should be the same for all the injectors.
Installation of the fuel rail together with injectors is performed in the reverse sequence. The following points should be noted when installing:
• Replace the O-rings at all opened connections. (when replacing the front O-ring, make sure the plastic cap is not removed from the injector head. The O-ring must be pulled off over the plastic cap).
• Coat O-rings with clean engine oil.
• Check to make sure that the retainer clamps are properly seated.
• When screwing fuel rail to intake manifold, tighten to: 10 Nm
- Bleed air from fuel system => [ Bleed air from fuel system ] Fuel Pressure Regulator and Holding Pressure, Checking