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Beryl Gardner
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1 Page 1 of 6 NO START - ENGINE CRANKS OKAY General Inspection 1. Ensure proper starting procedure is being used. 2. Visually check vacuum hoses for splits, kinks and improper connections. See underhood emission control information label. Check ignition wires for cracks, hardness and improper connections at distributor cap (if equipped) and spark plugs. 3. Remove spark plugs. Check and replace if necessary. 4. Remove distributor cap (if equipped) and check for moisture, dust, cracks, burns, and arcing to ground through coil mounting screws or rotor. 5. Try to turn distributor shaft by hand. Drive gear pin may be broken. 6. If vehicle has been exposed to very cold temperatures, ensure oil is of proper viscosity and not contaminated with gasoline. Ignition System Disconnect tachometer wire at distributor tachometer terminal (if equipped). A shorted tachometer or tachometer circuit prevents vehicle from starting. Ensure TP sensor and coolant sensor codes are not present and sensors are not out of calibration. Check for battery voltage at "+" terminal of ignition coil with ignition on. See Fig Repair as necessary. Connect Spark Tester (ST-125) to end of one plug wire. Crank engine. If spark is present, check fuel delivery. If spark does not occur, disconnect 4-wire EST connector at distributor (if equipped) and check for spark at ignition coil tower using Spark Tester (ST-125). If spark now occurs, check cap and rotor for damage or wear. Check for open in coil wires. If spark does not occur, reconnect EST connector. Leave spark tester connected to coil tower for remainder of test. Disconnect ignition coil Black 2-wire connector, and check voltage on "C" and "+" terminals with ignition on. If voltage on both terminals is 10 volts or greater, go to next step. If voltage on both terminals is less than 10 volts, repair wire from "+" terminal on module to "B" terminal on coil Black 2-wire connector. If voltage is less than 10 volts on "C" terminal only, check for open or short to ground in circuit from "C" terminal of ignition module to ignition coil. If circuit is okay, problem is faulty coil or coil connections. Connect voltmeter between ground and tachometer terminal at coil with ignition on. Tachometer terminal may be taped back against harness. If voltage is greater than 10 volts, go to step 9). If voltage is 1-10 volts, replace ignition module and check for spark at coil tower using Spark Tester (ST-125). If voltage is less than one volt, repair open in tachometer lead or tachometer connector. After repairs, recheck voltage at tachometer terminal. Connect test light between ground and tachometer terminal. Crank engine. If test light remains on (steady), go to next step. If test light flashes, replace ignition coil with a known-good unit and recheck for spark. If spark does not occur, reinstall original ignition coil and replace ignition module.

2 Page 2 of Remove distributor cap (if equipped). Unplug ignition module pick-up coil connector. Connect voltmeter between ground and tachometer terminal. Turn ignition on. Using jumper wires, connect positive end of a known-good 1.5-volt battery to terminal "P" of module. Observe voltmeter at tachometer terminal as negative end of test battery is momentarily grounded to distributor housing. If voltage at tachometer terminal does not drop, check ignition module ground. Check for open in wires from ignition coil to module. If all is okay, replace ignition module. If voltage at tachometer terminal drops, check for spark at spark tester as jumper is removed from terminal "P". If spark does not occur, go to next step. If spark occurs, check pick-up coil connections. Check for ohms resistance at pick-up coil leads. Ensure leads are not shorted to ground. Repair as necessary. Test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil, and touch terminal "P" again. If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil, and check coil wire from distributor cap (if equipped). If no problem is found, replace ignition module. Fuel System (TBI) Before checking fuel system for a no-start condition, check ignition for adequate spark. Check for proper fuel pump pressure (9-13 psi) and capacity (one pint in 30 seconds). See A-7, BASIC FUEL SYSTEM CHECKS. Crank engine, and watch for injector spray. If injector spray occurs, go to step 5). If no spray occurs, disconnect injector harness. Check for battery voltage at harness with ignition on. Battery voltage should be present on one injector terminal. If battery voltage is not present, check for blown injector power fuse. If battery voltage is present on both terminals, check for wires shorted together. If battery voltage is present on only one terminal, connect injector test light to injector harness. Crank engine, and note light. If light flashes, check for stored ECM codes. See DIAGNOSTIC CIRCUIT CHECK. If no codes are present, refer to HARD START symptom in TESTS W/O CODES article in the ENGINE PERFORMANCE section. If light does not flash, momentarily touch test light from battery voltage to ECM RPM reference terminal (circuit No Purple/White wire). Each time test light is removed from ECM RPM reference terminal, injector test light should flash. If test light does not flash, check for open in RPM reference wire or injector drive (ground) circuit. If wiring is okay, replace faulty ECM. Before replacing ECM, check ECM power and ground circuits. Disconnect injector harness, and crank engine. If injector spray or leakage occurs, a no-start condition may be caused by excessive fuel being delivered during cranking. Repair faulty injector or injector seal. If no spray or leakage occurs, refer to HARD START symptom in TESTS W/O CODES article in the ENGINE PERFORMANCE section. Fuel System (4.3L CPI) Before checking fuel system for a no-start condition, check ignition for adequate spark. For fuel system testing, see FUEL SYSTEM PRESSURE TEST under A-7, BASIC FUEL SYSTEM CHECKS.

3 Page 3 of 6 Fig. 1: HEI Ignition & Injector Circuits (2.2L)

4 Page 4 of 6 Fig. 2: HEI Ignition & Injector Circuits (4.3L "S" & "T" Series Pickup With M/T)

5 Page 5 of 6 Fig. 3: HEI Ignition & Injector Circuits (4.3L "S" & "T" Series Utility With M/T & All Models With 4L60-E A/T - Except CPI) Fig. 4: HEI Ignition & Injector Circuits (4.3L With 4L60-E A/T & CPI)

6 Page 6 of 6 Fig. 5: HEI Ignition & Injector Circuits (All Engines With 4L80-E Transmission) 2008 Mitchell Repair Information Co., LLC.

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

ENGINE CONTROLS - BASIC TESTING INTRODUCTION 1991 Cadillac Seville 4.9L Eng STS The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for