VISUAL INSPECTION
Visually inspect all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and not pinched or cut. If necessary, see VACUUM DIAGRAMS - SIERRA & SILVERADO article to verify routing and connections. Inspect air induction system for possible vacuum leaks.
Diagnosis
- Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000-2500 RPM and note gauge. If reading exceeds 1.25 psi (.09 kg/cm 2 ), exhaust system is restricted.
- Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exist, check for restricted catalytic converter. Replace as necessary.
NO-START DIAGNOSIS
Note. For terminal and circuit identification, see WIRING DIAGRAMS .
- Definition - No-start is defined as engine cranks properly, but does not start. Engine may fire a few times.
Circuit Description
This system includes Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor, ignition coil with Ignition Control (IC) module, secondary wires, spark plugs, and circuit conductors and connectors.
PCM controls ignition system and PCM monitors input signals from various engine sensors. The PCM controls dwell of ignition primary coil, computes desired spark timing and firing of ignition system via an IC timing control circuit to ignition control module.
Diagnostic Aids
Engine mechanical conditions may prevent distributor from rotating. Inspect following if distributor rotor does not rotate: A broken distributor drive shaft, worn or broken distributor drive gear, or worn/broken camshaft timing chain and gears. An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation.