Ignition.....
 

I’ve been having issues with my Chevelle lately as it won’t stay running at idle and spit/ sputters at higher rpm. I’ve changed everything in the ignition, it’s all new, distributor, coil, wires, plugs, etc... I’m currently running a Mallory Unilite mechanical distributor and coil, that’s it. Nothing fancy.

I noticed tonight that when I have the timing light on it, the light/strobe will stop flashing and then it will die shortly after that unless I rev it up to keep it running. If I keep the timing advance, a lot, it doesn’t seem to do it but as soon as I get it lower than 20* advance, it won’t stay idling.

It seems that when I rev the motor up, the timing retards for a second, then advances......?

There is a back story, one time when I was working on it, I started the car up and it ran fine but it started to smoke between the brake booster and the firewall. I accidentally forgot to hook up a ground wire to the ignition and a wire, not sure what it went to, got hot and was grounding out on the brake booster bracket. This always a couple years ago......I’m not sure if that has anything to do with the issue I’m having now or not.

Any thoughts on what might be the problem or how to diagnose it? I hate to keep buying parts if it’s not justified but I’m thinking of replacing the engine wire harness.......I’m not very good with electrical on a car but in so have a friend who is. I’m thinking we/he needs to check voltage on everything to see it there’s an issue.

Thanks in advance, Kurt

I had a friend who said to use a wire directly from the battery to the coil to bypass the harness and see if that works. I’m going to try that tonight.....if I get time.

Kurt

You could just measure coil voltage with it running. I have burned up a Mallory box putting full 12v to it. Your resistor wire could be giving you fits.

maybe try a stock factory distributor set up using stock wires, harness etc. and see if it starts, idles and runs. maybe process of elimination? Good luck KB.

If you are going to use a jumper wire for + then I would also use a jumper for -. You might use a Chrysler resistor with the + jumper to protect the ignition.

I literally just ran a wire directly to the coil, through the 1.6 ohm resistor, from the positive side of the battery and it fire right up with zero issues. The timing is set at 17* initial and 38* total....for now. Time to order a new engine wire harness!!!!

Thanks for all the replies, Kurt

Glad ya found it Kurt.

Good to hear. Good advice!!:3gears:

Isn’t the factory positive wire to the coil a resistor wire ? If so using a resistor would lower the voltage more ...

He bypassed the harness (with resistor wire) and ran a wire direct from battery and used a 1.6 ohm resistor. Basically simulating what the harness should do, and found the harness is at fault.

Yes......the factory distributor wire is a resistor wire which is about 8 volts.....I didn’t know that until yesterday.....lol. The Mallory coil needs anywhere from 6-9 volts.....so the 1.6 resistor was still within tolerance, I believe?

I HAD a Mallory Hyfire CDI box installed at one time. I eliminated it because I was trying to do a process of elimination to locate my issue. So actually, the CDI box was supposed to be getting 12 volts but was really only getting 8 volts.....through the factory resistor wire.

So when I was still having issues, I purchased the new Unilite distributor, I read that it needs a 1.6 ohm resistor.....which I installed. Technically, I didn’t need that as the factory wire was already at 8 volts.....but again, I didn’t know that. So when I bypassed the resistor wire and went directly from the battery to the coil....everything was in normal condition.

I will be reinstalling the Mallory Hyfire CDI box which will need 12 volts. So I ordered a new engine wire harness from America Auto Wire that will have the correct 12 volts to the CDI box. If I need to lower the volts, I can reinstall the resistor directly to the coil.

Kurt

See, just as I had said.... I knew all along you would figure it out :)

Dan

Just to add, when you are starting the engine key in start position and starter turning the resistor wire in the harness is bypassed and the coil receives full12 volts. After you release the key to the run position (engine running) the resistor power wire applies the reduced voltage 8 ish volts. Basically you get a hotter spark on startup and once running reduced to preserve the point s

btw, the point of the resistor isn't to reduce the voltage, it's to limit the current that the coil sees. ;)

You are technically correct, but it's easier to measure the voltage drop. Obviously the voltage drop represents a reduction in current. In simple terms voltage is pressure and current is flow. If you decrease the pressure(voltage), flow (current) is decreased. :biggthumpup: