1974 not starting
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2nd Gear
Joined: Aug 2025
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1974 not starting
My truck has been giving me some spark trouble, I have checked everything I thought of, checked the ignition modules, replaced coil, check continuity on all wires from module to coil and distributor, checked the start relay, pick up coil is reading 591, truck will crank, just no spark, I will try again after resitting all the connections, but other than that, I am at a loss, I don't know what else to check,
Lead Driver
Joined: Jul 2017
Posts: 9,618
Likes: 1,186
From: San Jose, CA
Pull the distributor cap off and crank the engine. If the rotor turns consistently, move onto to the next test.
Turn the key to ON and check for voltage at the positive terminal of the coil. If no voltage, find out why. If it does have it, move onto the next test.
Disconnect the brown wire from the starter relay. This eliminates the starter relay as any part of the problem. But you can still measure voltage on the starter relay in the START condition. Should be a full 12V on the small “I” terminal where the brown wire was previously.
Test the new coil. You can test it with an ohmeter, and you can test it by mimicking the opening and closing of the trigger to see if it will produce a spark.
Since you tested the ignition module with an ohm-meter, you should now test it with the volt-meter. Separate the four wire connector and check for voltage on the wires.
those are just a few more tests to help narrow things down a little more.
Turn the key to ON and check for voltage at the positive terminal of the coil. If no voltage, find out why. If it does have it, move onto the next test.
Disconnect the brown wire from the starter relay. This eliminates the starter relay as any part of the problem. But you can still measure voltage on the starter relay in the START condition. Should be a full 12V on the small “I” terminal where the brown wire was previously.
Test the new coil. You can test it with an ohmeter, and you can test it by mimicking the opening and closing of the trigger to see if it will produce a spark.
Since you tested the ignition module with an ohm-meter, you should now test it with the volt-meter. Separate the four wire connector and check for voltage on the wires.
those are just a few more tests to help narrow things down a little more.
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