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Failure To Start Test

  1. Measure and record battery voltage. Check battery specific gravity, which must be 1.220 (temperature corrected) to deliver proper voltage to ignition system.
  2. Remove coil secondary wire from distributor cap and hold 1/4" from a good ground. Prepare a special jumper wire assembly. See Fig 1 . With ignition on, momentarily touch special jumper wire to ground and coil negative terminal. A spark should be obtained at secondary wire.
    Fig 1: Special Jumper Assembly for Grounding Coil Negative Terminal
    G1237
  3. If spark was obtained, proceed to step 6). If no spark resulted, turn ignition off and disconnect 10-way harness connector from computer. See Fig 2 . Turn ignition back on and again. Using special jumper wire, connect negative terminal momentarily to ground. Spark should be obtained.
  4. If spark was obtained, but engine will not start, computer output is shorted. Replace computer. If no spark resulted in step 3), connect positive lead of voltmeter to coil positive terminal and negative lead to a good ground. Reading should be within one volt of battery voltage. If not, check wiring between battery and coil positive terminal.
  5. If correct voltage was recorded in step 4), move voltmeter positive lead to coil negative terminal. Again, voltage should be within one volt of battery voltage. Replace ignition coil if voltage is not present or if voltage is present, but no spark results when shorting negative coil terminal with jumper wire.
    Fig 2: Distributor & Computer Harness ESC Test Connectors
    G1238
  6. If spark was obtained in step 2) or if in step 5) correct voltage was obtained but engine would not start, hold carburetor switch open with a thin cardboard insulator. Measure voltage between carburetor switch and ground. Reading should be within one volt of battery voltage. If so, proceed to step 10).
  7. If battery voltage was not indicated in step 6), turn ignition off and disconnect 10-way harness connector from computer. Turn ignition on. Connect positive lead of voltmeter to cavity "2" of connector and negative lead to ground. Reading should be within one volt of battery voltage.
  8. If no battery voltage is present, check wiring from battery to ignition switch to cavity "2". Use an ohmmeter to check continuity of wires. Correct problem and repeat step 7). If voltage was present in step 7), turn ignition off. Connect ohmmeter leads to carburetor switch terminal and cavity "7" of 10-way connector.
  9. If no continuity is found, check for open wire between cavity "7" and carburetor switch. If continuity was indicated, connect ohmmeter leads to cavity "10" and to a good ground. If continuity exists, replace computer, as correct power is entering computer, but not leaving it. Repeat step 6). If no continuity existed between cavity "10" and ground, check for an open wire in the ground system.
  10. Reconnect 10-way harness connector to computer. Turn ignition on and hold secondary coil wire 1/4" from a good ground. Disconnect 3-wire distributor connector from distributor. Attach jumper wire between cavities 2 and 3 of harness connector. A good spark should jump from coil wire to ground.
  11. If spark resulted, but engine will not start, replace Hall Effect Pick-Up. Before replacing, always ensure rotor shutter blades are grounded. Connect one ohmmeter lead to a good ground and touch other lead to shutter blade. See Figure . If there is no continuity, push down on rotor to seat against shaft. If there is still no continuity, replace rotor. If shutter blade is grounded, then replace Hall Effect Pick-Up.
  12. If no spark resulted in step 10), connect voltmeter positive lead to distributor harness connector cavity "1" and negative lead to ground. Reading should be within one volt of battery voltage. If no battery voltage is present, proceed to step 15). If voltage was correct, turn ignition off and disconnect 10-way harness connector from computer.
  13. Connect ohmmeter leads between cavity "2" (Black/Light Blue wire) of the distributor harness connector and cavity "9" of 10-way connector. Then connect leads to cavity "3" (Gray wire) of distributor harness connector and cavity "5" of 10-way connector.
  14. If no continuity is present, repair open wires. If continuity exists, replace computer, as power is going into computer, but not coming out. Repeat step 10).
  15. If there was no battery voltage in step 12), turn ignition off, disconnect 10-way connector. Connect ohmmeter leads to cavity "1" of distributor harness connector and cavity "3" of 10-way connector. If no continuity exists, repair wire and repeat step 10).
  16. If continuity existed in step 15), turn ignition on and check for battery voltage with voltmeter positive lead in cavity "2" of 10-way connector and negative lead in cavity "10". If battery voltage is present, but vehicle will not start, replace computer and repeat step 10). If no battery voltage is present, check ground wire and repeat step 10).
CAUTION: Before replacing a computer that is thought to be defective, disconnect both the 10-way and 14-way connectors from the computer. Visually inspect inside of both connectors to ensure cavity terminals have not been spread or damaged, preventing them from making proper contact with mating computer pins when installed. Reinstall connectors to computer.
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