424 voltage question

capefair424 · Aug 12, 2011

On my 1967 424 the volts at the hot side of the coil in on position are 12.2 volts but when the tractor is running the voltage is jumping all over the place from like 27+ to sometimes a negative voltage. Any help would be great. Thanks

Bob · Aug 12, 2011

Apparently, you are using a digital meter.

Some digital meters get freaked out by the electrical "noise" from ignition systems and produce goofy readings.

You've just learned that!

Janicholson · Aug 12, 2011

THe voltage when on is chopped by the points and coil/condenser electrical activity. This chopped voltage is sampled by your meter and displayed as what was instantly there. (the actual voltage will be an average of these spiles and "noise" To get a true reading you will need either a pretty expensive digital meter (Fluke or similar) or a cheap analog meter with a needle that indicates voltage on a background scale. The cheap meter averages incoming volts, and ignores spikes. Jim

capefair424 · Aug 12, 2011

I should have added that the tractor runs real rough and especially rough after it warms up. I have put new plugs, wires, points and condensor, and coil on and am at a loss as to what is going on. When I used the test light to set the timing the mark at 17 degrees advanced jumped around on both sides of the mark. Thanks for all your help

Janicholson · Aug 12, 2011

The distributor cam is supported by a bushing. if you can feel any side to side play in the shaft, it needs to be rebuilt. The max motion is .001' measured with a dial indicator. Jim

424 voltage question

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