Q: Truck will crank, but engine won't start - 1973 Chevrolet K20

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The old battery in my car would not hold a charge, so I replaced it with a new one. After installing the new battery, the truck will crank, but the engine will not start. I held a plug wire next to ground to test for spark, but there was nothing. I also used the same technique to test the coil wire - nothing. Next, I tested for voltage across the input wires to the coil. When the ignition engaged, there were only 4 volts. Next, at the ignition fuse, in the fuse panel, I tested for voltage and saw 12 volts. I know that from the starter solenoid is the only other direction that the voltage comes from. When I tested there, it was 12 volts going into the solenoid, however only 4 were coming back to the coil. My truck’s starter is a new one that I installed several months ago. Next to the distributor is a small capacitor-looking part in the same bracket with the coil. I don't know if this is a resistor or a capacitor. There is only one connection that goes to the coil’s back side connection. I have been researching for wiring diagrams but so far haven't found any. Could you please give me whatever help you can for these problems?

Hello there, thanks for writing in. The wiring diagram for the ignition system of your vehicle is pretty simple. Power flows from the ignition switch to the coil. When the engine is cranked, the points open and close to create voltage in the coil secondary windings. This creates the high voltage needed to fire the spark plugs, which is sent to the distributor.

If there is no spark, suspect a faulty coil, coil wire, cap rotor, points or distributor. The wiring between the ignition switch and coil could also be bad. A faulty starter will not prevent the engine from getting spark.

It sounds like you’ve already spent a lot of time on this issue; if you’d like further assistance, consider having one of our certified automotive technicians come to your home or office to diagnose and repair your vehicle properly.

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