Fuel Injectors, Checking

Fuel Injectors, Checking

Special tools, testers and auxiliary items required
- Multimeter.
- Diode test lamp (12 V).
- 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.
- 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 degrees C)

If the specified value was not obtained:
- Replace the malfunctioning Fuel Injector.

If the specified value was obtained:

Checking activation and wiring







- Connect a diode test lamp (12 V) 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.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J623.







- 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.

Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes