Engine Cranks But Does Not Run

Circuit Description

Diagnostic Aids
If no trouble is found in the fuel pump circuit or the ignition system and the cause of an Engine Cranks But Will Not Run has not been found, check for the following conditions:
- Perform the Fuel Injector Coil Test.
- An after-market Vehicle Theft Deterrent system could cause a Start then Stall or a No Start condition
- Fouled spark plugs
- An EGR valve stuck open
- Water or foreign material in the fuel system
- A grounded or intermittently grounded Ignition Control (IC) signal circuit
- Restricted exhaust system
- Check the following ignition components:
- Worn distributor cap
- Worn distributor rotor
- Check ignition wires by lightly spraying them with water for intermittent no starts. Refer to Engine to diagnose the following:
- Cylinder valve timing
- Loose or broken timing chain
- Low compression
- Worn camshaft lobes
- Bent or burned intake or exhaust valves

The VCM has integrated IC circuits that are fault protected; therefore, if a circuit has failed, the integrated IC may not be damaged. If that is the case, the IC will keep the circuit open until the fault in the circuit has been corrected.

When the fault has been corrected, reinstall the VCM and check the circuit. Replace the VCM only if the circuit is still inoperative.

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 4:

Steps 5 - 8:

Test Description
The numbers below refer to the step numbers on the diagnostic tables.
2. If the engine starts, the problem could be intermittent. Basic engine mechanical problems, the vehicle theft deterrent (VTD) system (if equipped) and poor connections could cause a no start condition.
3. This step will determine if the cause of the no start or start and stall is related to the VTD.
4. If the signal is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems.
5. If the engine coolant sensor is below -30 °C (-22 °F), the VCM provides fuel for this extremely cold temperature which will severely flood the engine.
6. Voltage at the spark plug is checked using the J 26792 spark plug tester tool. No spark indicates a basic ignition problem.
7. This test will determine if there is fuel pressure at the fuel injection unit and holding steady.
8. Use the J 34730-350 injector test lamp in order to test the injector circuits. A blinking lamp indicates that the VCM is controlling the injector.