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HOMESERVICE MANUALSCHEVROLET1993CAMARO Z28, STANDARD, M29REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGNO START DIAGNOSIS (A-3)NO START - ENGINE CRANKS OKAY (4.9L WITH HEI DISTRIBUTOR)IGNITION SYSTEM
1993 Chevrolet Camaro Z28, Standard, M29

Ignition System

1993 Chevrolet Camaro Z28, Standard, M29SECTION Ignition System
  1. Disconnect White tachometer wire at distributor TACH (C-) terminal (if equipped). A shorted tachometer or tachometer circuit will prevent vehicle from starting.
  2. Connect Spark Tester (ST-125) to end of one plug wire and crank engine. If spark occurs, check spark plugs and fuel delivery.
  3. If spark does not occur, check a second wire. If no spark occurs, check voltage at BAT terminal at distributor while cranking engine. If reading is less than 7 volts, repair open circuit between BAT terminal and ignition switch.
  4. If reading is greater than 7 volts, check voltage on TACH terminal with ignition on, engine off. If reading is 1-10 volts, replace module. Fabricate an HEI coil spark tester by trimming a spark plug boot and connecting it to Spark Tester (ST-125). See Fig 1 . Crank engine. If spark occurs, system is okay. If no spark occurs, replace ignition coil.
  5. If reading at TACH terminal is less than one volt, repair faulty ignition coil connection or replace faulty ignition coil.
  6. If voltage reading at TACH terminal of distributor is greater than 9.9 volts, remove and invert distributor cap with wires connected. Fabricate an HEI coil spark tester by trimming a spark plug boot and connecting it to Spark Tester (ST-125). See Fig 1 . Crank engine.
  7. If spark occurs, check cap for cracks, water or other defects. Verify correct pick-up coil is used. Proper pick-up coil has a Black connector.
  8. If spark does not occur, turn ignition off and disconnect pick-up coil leads from module. Turn ignition on. With voltmeter connected to distributor TACH terminal and fabricated coil spark tester connected, momentarily touch test light, connected to battery voltage, to ignition module terminal "P". See Fig 2 .
  9. If voltage at TACH terminal does not drop, check ignition module ground and for open in wires from ignition coil to module. If all is okay, replace ignition module.
  10. If voltage at TACH terminal drops, check for spark at spark tester as test light is removed from terminal "P". If spark does not occur, go to next step. If spark occurs, check distributor grounds for opens. Repair as necessary. If no opens are present, check pick-up coil connections and for 500-1500 ohms resistance at pick-up coil leads. Repair as necessary.
  11. If spark does not occur, test ignition module with module tester. If module tests okay, check ignition coil wire. If module tester is not available, replace ignition coil and again touch terminal "P." If spark occurs, system is okay. If spark does not occur, reinstall original ignition coil and replace ignition module.
Fig 1: Checking HEI Distributor Coil Spark (4.9L Cadillac)
G90F13214Courtesy of GENERAL MOTORS CORP.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.