Chart A-3 - Engine Cranks But Will Not Run
NOTE:
Before performing this test, check battery condition, engine cranking speed and tank for adequate fuel. Test numbers refer to numbers on diagnostic chart.
- When ignition is turned on, the CHECK ENGINE light should come on, indicating battery voltage and ignition voltage are being supplied to ECM. If NO ALDL data (trouble codes) are displayed on scan tester, this may be due to ECM problem. See appropriate SELF-DIAGNOSTICS article to diagnose CHECK ENGINE light. If TPS voltage is more than 2.5 volts, engine may be in "clear flood" mode, which will cause starting problems. Engine will not start without ignition reference signals. Scan tester should indicate engine speed (RPM) during cranking.
- Because electronic ignition system uses 2 plugs and wires to complete circuit of each coil, opposite spark should be left connected. If RPM is indicated during cranking, ignition control module is receiving crank signal. If no spark is present, ignition control module is not triggering coils. See IGNITION CHECKS to diagnose ignition problems related to no-spark condition.
- Test light should blink, indicating ECM is in control of injectors. Brightness of light is not important.
- This test checks ignition control module reference pulses, wiring and ECM. Connect test light connected to 12-volt source, and momentarily touch Yellow/Red wire. A reference pulse should be generated. If RPM is indicated, ECM and wiring are okay.
- High resistance in spark plug wire could cause a no-start condition. If a spark plug wire is faulty, replace wire and retest system.
- This test will check injector harness for an open or shorted circuit after engine harness connector.
- A shorted or open injector could be cause of engine cranks but will not run symptom.
- Test for short to ground in injector driver circuits.
- Check for voltage at injector. An open in Red/Green wire at splice from main relay would result in engine cranks but will not run symptom.
- Test engine control module for injector pulse.
- A faulty resistor module could be cause of no-start condition. If module is faulty, recheck engine control module after replacing resistor module.
- This test will determine if 12-volt supply and good ground are available at ignition control module.
- This test checks for battery voltage in ignition feed circuit to ignition control module.
- This test checks for continuity of crankshaft position sensor and connections.
- Voltage will vary depending on engine cranking speed.