Fuel Injection Quantity, Checking For Leaks and Spray Pattern
Diagnostic Procedures
Fuel Injection Quantity, Checking for Leaks and Spray Pattern
Test Requirement
• Fuel pressure OK.
Fuel Rail Pipe, Removing
- Remove engine compartment cover.
- Disconnect vacuum hose from fuel pressure regulator.
- Disconnect connector from fuel injectors, remove cable ties if necessary.
- Remove fuel rail from intake manifold and pull off from intake manifold with fuel injectors upward.
Checking for Leaks
- Insert fuel injector to be tested in a measuring glass from injection quantity test device (VAG1602).
- Connect test box (VAG1598/31) at wiring harness to Engine Control Module (ECM), do not connect ECM, refer to Repair Information.
- Bridge terminals 1 and 65 at test box using adapter cables from connector test kit (VAG1594A) (this step supplies Ground (GND) to one side of relay coil of Fuel Pump (FP) relay).
- Switch ignition on.
• After switching ignition on, Fuel Pump (FP) will run continuously, even with engine not running. This is true because: Fuel Pump (FP) relay is supplied with B+ via central electronics after ignition is switched on. Fuel Pump (FP) relay receives Ground (GND) via the cable bridge in test box.
- Check proper seal of fuel injectors (visual inspection). With Fuel Pump (FP) running, only 1 to 2 drops per minute may drip out per injector.
- If fuel loss is greater, stop Fuel Pump (FP) from running (switch ignition off) and replace faulty fuel injector.
Injection Quantity, Checking
- Insert fuel injector to be tested in a measuring glass from injection quantity test device (VAG1602).
- Connect one terminal of fuel injector to engine Ground (GND) using an adapter cable and an alligator clip from connector test kit (VAG1594A).
- Connect the second terminal of fuel injector to B+ using remote control (VAG1348/3A), adapter cable (VAG1348/3-2) and assisting cable.
- Bridge terminals 1 and 65 at test box using wires from adapter test kit (VAG1594A).
- Switch ignition on.
• Fuel Pump (FP) must run.
- Operate remote control (VAG1348/3A) for 30 seconds.
- Perform measurement on all fuel injectors.
- After all four fuel injectors (bank 1/bank 2) have been activated, place measuring glasses on an even surface.
Specified value for each fuel injector: 105 to 125 ml
If specified value is not reached at all fuel injectors.
- Check fuel pressure:
• Vehicles with return line => [ Fuel Pressure Regulator and Residual Pressure with Return Line, Checking ] Fuel Pressure Regulator and Residual Pressure With Return Line, Checking
• Vehicles with fuel system without return flow => [ Fuel Pressure Regulator and Residual Pressure without Return Line, Checking ] Fuel Pressure Regulator and Residual Pressure Without Return Line, Checking
If specified value is not reached at one fuel injector.
- Replace respective fuel injector.
• Also check spray pattern when checking injection quantity. Spray pattern must be the same for all injectors
Installation of fuel rail with fuel injectors is the same in reverse order. Observe the following points when installing:
• Replace O-rings at all opened connections. (Never remove plastic cap from valve head to replace front O-ring - lift O-ring off over plastic cap).
• Lightly lubricate O-rings with clean engine oil.
• Check clip for unobstructed fitting.
• Tighten fuel rail to intake manifold to 10 Nm.