Fuel Injectors, Checking

Fuel Injectors, Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Diode test lamp (12V).

• Wiring diagram.

Test requirements

• The Fuel Injectors (N30, N31, N32, N33, N83, N84, N85, N86) (S116) OK.

• The Engine Speed (RPM) Sensor (G28) OK, checking.

• Battery voltage at least 12.5 volts.

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

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

- Observe safety precautions.

- Observe rules for cleanliness.

Procedure

- Remove the engine cover with air filter Refer to Fuel Injection and Ignition Repair Information.

- Disconnect the Fuel Injector electrical harness connectors from Fuel Injectors (N30, N31, N32, N33, N83, N84, N85, N86).

Checking internal resistance

- Using a multimeter, check the Fuel Injector electrical terminals 1 to 2 for resistance.





Specified value: 12.0 to 20.0 ohms (at approx. 20° C)

If the specified value was not obtained:

- Replace the malfunctioning Fuel Injector Refer to Fuel Injection and Ignition Repair Information.

If the specified value was obtained:

Checking activation and wiring

- Connect a diode test lamp (12V) to the electrical harness connector terminals 1 and 2 of the Fuel Injector to be tested.





- Operate the starter and test the activation of the Fuel Injector.

LED should flicker.

- Switch the ignition off.

If LED does not flicker:

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to Fuel Injection and Ignition Repair Information.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) ( J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- Using a Multimeter, check the Fuel Injector electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T121 terminals for an open circuit.









Specified value: 1.5 ohms Max.

If the specification is not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J623).

- Install the engine cover with air filter Refer to Fuel Injection and Ignition Repair Information.

Final procedures

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.