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Fuel Injectors, Checking






Diagnostic Procedures


Fuel Injectors, Checking

Special tools, testers and auxiliary items required

• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)

• Voltage tester (V.A.G 1527)

• Test adapter kit (V.A.G 1594)

• Wiring diagram

Test conditions

• Motronic Engine Control Module (ECM) Power Supply Relay (J271) -position 4- must be OK, check:

• Electrical fuel pump relays must be OK.

• Battery voltage (both batteries) must be at least 11.5 Volts.

• All electrical consumers such as, lights and rear window defroster must be switched off.

• For vehicles with automatic transmission, selector lever must be in " P".

• Parking brake must be engaged.

• The Ground (GND) connections between engine and body must be OK.

• Engine Speed (RPM) Sensor must be OK, checking => [ Engine Speed Sensor, Checking ].

• Ignition switched off.

• Fuse -29- for fuel injectors 1 to 12 in right instrument panel fuse holder must be OK:

Right instrument panel fuse holder





Test Sequence

- Remove intake manifold upper part (along with both intake manifold side parts).

- Remove connector for fuel injectors 1 to 12 ((N30, N33, N83, N86, N299, N302)).





• Cylinder bank 1 with cylinders 1 through 6 is located at right in direction of travel.

• Cylinder bank 2 with cylinders 7 through 12 is located at left in direction of travel.

Resistance values of fuel injectors, checking

- Test resistance of fuel injectors between terminals. Specification: 14.0 to 16.0 ohms

If specification is not attained:

- Replace faulty fuel injector.

When installing fuel injector, observe the following:

• Replace O-rings on all injectors and lightly moisten with clean engine oil.

• Insert fuel injectors into fuel rail perpendicular and in correct position, and secure them with retaining clips.

• Position fuel rail with secured fuel injectors on intake manifold and apply uniform pressure to press it in.

• The connectors must audibly engage in the injectors when pushed on.

- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.

Checking voltage supply

- Connect diode test lamp to connector of fuel injector to be tested terminal 1 + Ground (GND).





- Operate starter and check voltage supply for fuel injectors. LED must light up

- Switch ignition off.

If LED does not light up:

- Check wire between 2-pin connector terminal 1 and corresponding fuse in E-Box (in plenum chamber, right side) for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms





- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.

Actuation and voltage supply, checking

- Connect diode test lamp to connector terminals 1 + 2 of fuel injector to be checked.





- Operate starter and test activation of corresponding Engine Control Module (ECM) for fuel injector. LED must flicker

- Switch ignition off.

If LED does not flicker:

- Check wires to Engine Control Module according to wiring diagram.

Checking wires to Engine Control Module

Cylinder bank 1

- Connect test box to Engine Control Module (ECM) (J623) wiring harness on connecting test box for wiring test, refer to Repair Manual,

Cylinder bank 2

- Connect test box to Engine Control Module (ECM) 2 (J624) wiring harness on connecting test box for wiring test, refer to Repair Manual,

Cylinder bank 1 and 2

- Check wires between test box and 2-pin connector for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms





Cylinder bank 1





Cylinder bank 2





Cylinder bank 1 and 2

- Check wires for short circuit to B+ and Ground (GND). Specification: infinite ohms

- Erase DTC memory of Engine Control Module (ECM) => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.

If no malfunction is detected in the wiring, replace the engine control module.

Fuel Injectors, Checking Injection Quantity and Seal





Special tools, testers and auxiliary items required

• Torque wrench (V.A.G 1331) (5 to 50 Nm)

• Remote control (V.A.G 1348/3A) with adapter cable (V.A.G 1348/3-2)

• Test adapter kit (V.A.G 1594 A)

• Injection Rate Tester (VAG1602)

Test conditions

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

• Ignition switched off.

Test Sequence

- Remove intake manifold upper part (along with both intake manifold side parts).

- Disconnect harness connectors of fuel injectors 1 to 12 ((N30) to N33, N83 to N86, N299 to N302).





• Cylinder bank 1 with cylinders 1 through 6 is located at right in direction of travel.

• Cylinder bank 2 with cylinders 7 through 12 is located at left in direction of travel.

- Remove fuel rail completely along with fuel injectors (fuel lines remain connected), fuel rail with fuel injectors, disassembling and assembling. Refer to Repair Manual

- Connect test box to Engine Control Module (ECM) 2 (J623) wiring harness on connecting test box for wiring test, refer to Repair Manual,

Checking for leaks.

Checking injection quantity.

Checking for Leaks

- Bridge sockets 1 + 65 of test box with respective adapter cables. Fuel Pump (FP) (G23) must run.

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

- Switch ignition on.

- Check injectors for leaks (visual inspection). Only 1 to 2 drops per minute may emit from each valve when fuel pump is running.

- Disconnect connection between test box sockets.

- Switch ignition off.

If fuel loss is greater:

- Replace faulty fuel injector.

When installing fuel injector, observe the following:

• Replace O-rings on all injectors and lightly moisten with clean engine oil.

• Insert fuel injectors into fuel rail perpendicular and in correct position, and secure them with retaining clips.

• Position fuel rail with secured fuel injectors on intake manifold and apply uniform pressure to press it in.

• The connectors must audibly engage in the injectors when pushed on.

- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.

- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
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