Failure To Start

NOTE: Perform Ignition System Starting Test first. Failure to do so may result in lost diagnostic time or incorrect test results.

Measure and record battery voltage. Measure specific gravity, which must be at least 1.220 (temperature corrected) to deliver proper voltage.
Turn ignition switch "OFF". Disconnect 10-wire connector from spark control computer. Repeat step 1) of Ignition System Starting Test. If spark results, replace spark control computer.
If no spark is obtained, check voltage at positive terminal of ignition coil. With ignition switch "ON", connect positive voltmeter lead to positive terminal of ignition coil and negative lead to a good ground. Reading should be within 1 volt of battery voltage. If not, check wiring between battery and coil positive terminal.
If voltage at positive terminal of ignition coil was correct, connect positive voltmeter lead to negative terminal of ignition coil and negative lead to a good ground. Again, voltage should be within 1 volt of battery voltage. If not, replace ignition coil.
NOTE: Check coil primary and secondary resistance before replacing ignition coil. However, if battery voltage exists on positive side, but not on negative side of coil, ignition coil normally requires replacement.
If voltage was correct at negative coil terminal, but no spark resulted in step 1) of Ignition System Starting Test, replace ignition coil.
If spark results, but engine will not start, turn ignition switch to the "RUN" position. Connect positive voltmeter lead to terminal 1 of 10-wire connector and negative lead to a good ground. See Fig 1.

Fig 1: Voltmeter Hookup for Checking Terminal 1 Voltage
Reading should be within 1 volt of battery voltage. If not, check wire for open and repair it, repeating this step once more. Reconnect 10-wire connector to computer.
If battery voltage was recorded in step 6), place a thin insulator (piece of paper) between curb idle adjusting screw and carburetor switch or make sure screw does not touch the switch. See Fig 2.

Fig 2: Checking Voltage at Carburetor Switch
Connect negative lead of voltmeter to a good ground. Turn ignition switch to "RUN" position, and touch positive voltmeter lead to carburetor switch terminal. Reading should be approximately 5 volts. If so, proceed to step 15).
If voltage was not at least 5 volts, turn ignition switch "OFF". Disconnect 10-wire connector from computer. Turn ignition switch back to "RUN" position. Connect positive voltmeter lead to terminal 2 of 10-wire connector and negative lead to ground. See Fig 3.

Fig 3: Voltmeter Hookup for Checking Terminal 2 Voltage
Voltage reading should again be within 1 volt of battery voltage. If not correct, check wiring between terminal 2 and ignition switch for opens, shorts or poor connections.
If voltage at terminal 2 was correct, turn ignition switch "OFF". Using an ohmmeter, check continuity between terminal 7 of 10-wire connector and carburetor switch terminal. See Fig 4.

Fig 4: Ohmmeter Hookup for Checking Carburetor Switch Wiring Harness
Continuity should exist. If not, check wire between connections for opens, shorts or poor connections. If continuity is present, use an ohmmeter with leads attached to terminal 10 and engine ground to check continuity of ground circuit. See Fig 5.

Fig 5: Ohmmeter Hookup for Checking Computer Ground Circuit
If there is continuity, replace spark control computer. If there is no continuity, check wire from terminal 10 to ground. If engine fails to start, proceed to step 15).
Turn ignition switch "OFF". Attach ohmmeter leads to terminals 5 and 9 of 10-wire harness connector to check run pick-up coil resistance and to terminals 3 and 9 to check start pick-up coil resistance. See Fig 6. Resistance should be 150-900 ohms for both pick-up coils. If so, proceed to step 17).

Fig 6: Ohmmeter Hookup for Checking Pick-Up Coil Resistance
If resistance is not 150-900 ohms, disconnect distributor connectors and attach ohmmeter leads to run pick-up coil leads and then to start pick-up coil leads coming from distributor. If resistance is now okay, wiring harness is defective. If resistance is still not 150-900 ohms, replace pick-up coil(s), as necessary.
Connect one lead of an ohmmeter to engine ground and touch other lead to each terminal of leads coming from 2 distributor pick-up coils. There should be no continuity. If continuity is indicated, replace pick-up coil.
Remove distributor cap and rotor and check reluctor-to-pick-up coil(s) air gap as described previously. Install distributor cap and reinstall all wiring. If engine fails to start, replace spark control computer. If it still fails to start, install original computer and retest.