1966 Buick Wildcat with 401 nailhead rebuilt distributor with breakerless installed and points removed. Ballast resistor works and drops voltage to 8.6 volts on positive side when car is running. I tested the coil and it reads 1.4 ohms. My question is when I test the negative side of the coil I am only getting 2.4-2.6 volts when running, is this normal? Car runs great, it should just rebuilt the nailhead now I am fine tuning. Thanks
You'll find this in a lot of the Chassis Manuals, These are the only tests described in the Chassis Manual, To test the system for proper functioning requires a volt meter. Connect the voltmeter between the positive side of the coil and ground. Turn the ignition switch to the run position. The reading should be 5.0-5.5 volts. It is important that the ignition points be closed for this test. If the points are open, the voltmeter reading will be full battery voltage. Bump the engine over until the points are closed, and check again. Again, 5.0-5.5 volts is the normal reading with the engine stopped, ignition key in the run position, and the voltmeter connected between the positive side of the coil and ground. The second part of the functionality test requires that you pull the coil wire out of the distributor, and ground it so the engine will not start. With voltmeter connected as before, crank the engine continuously, and observe the voltmeter. The reading should jump from the previous 5-5.5 volt reading up to 9 volts minimum. If it does not, it indicates a problem with the shorting switch inside the starter solenoid, or a wiring problem between the "R" terminal of the solenoid, and the coil. This will result in hard starting when cold.
Thanks Larry, I will try the tests. I have the service manual but it would take me forever to find that information.
Thanks so much Larry for your replies to this. Really helps us out. I’m having an issue with my 70 GS 455. I have a Mallory electronic conversion in a stock distributor and it just died. Trying to troubleshoot it and think it’s the module but wanted to check coil and other functions. Thinking about just **** canning it and going back to points. Maybe not as good but damn reliable
Yes, but some require the stock resistance wire, and others require full battery voltage like the GM HEI. The tests that the OP is performing on a running engine are meaningless. (See post #2).
