Circuit Description
The diagnosis for an engine that cranks but does not run must have three elements present before proceeding with the diagnostic table. The following conditions must exist:
| • | The battery must be adequately charged. |
| • | The engine cranking speed must be sufficient. |
| • | There must be an adequate amount of fuel in the fuel tank. |
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:
| • | Fouled spark plugs |
| • | An EGR valve stuck open |
| • | Low fuel pressure. Refer to Fuel System Diagnosis . |
| • | Water or foreign material in the fuel system |
| • | A grounded Ignition Control (IC) signal circuit may cause a No Start or a Start then Stall condition |
| • | Basic engine problem |
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.
Test Description
The numbers below refer to the step numbers on the diagnostic tables.
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If the signal is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems.
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If the engine coolant sensor is below -30°C, the VCM provides fuel for this extremely cold temperature which will severely flood the engine.
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Use the injector test lamp J 34730-350 in order to test the injector circuit. A blinking lamp indicates that the VCM is controlling the injector.
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Voltage at the spark plug is checked using the spark plug tester tool J 26792 . No spark indicates a basic ignition problem.
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This test will determines if there is fuel pressure at the fuel injection unit and holding steady.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
With the throttle closed is the TP sensor over the specified value? | 2.5 Volts | Go to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage | ||
Monitor the ECT sensor on the scan tool. Is the ECT sensor below the specified value? | -30°C | Go to DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage | ||
4 |
Does the fuel pump operate for 2 seconds? | -- | ||
Does the test lamp flash? | -- | |||
Is the spark present? | -- | Go to Enhanced Ignition System | ||
Is the fuel pressure beween the specified values? | 380-420 kPa (55-61 psi | Go to Fuel System Diagnosis | ||
8 | Repair the injector ignition feed circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
9 |
Does the engine start and continue to run? | -- | ||
10 |
Are any DTCs displayed? | -- | Go to The Applicable DTC Table | |
11 | Using the scan tool, select the Capture info and the Review info. Are any DTCs displayed that have not been diagnosed? | -- | Go to The Applicable DTC Table | System OK |
