Bad Coil?
 

If you remember in one of my other posts from a couple weeks ago I've had trouble with this '28 running well, or even running (backfiring) recently. We took it out yesterday for a couple miles in 78 degree weather. The two miles was about all it wanted. It started losing power and surging. There was some backfiring. I know that there are a myriad of things to check, but I got thinking about the coil. Could a failing coil cause this? I have a new one so I'm going to give it a try.

Re: Bad Coil?
 

The short answer is yes, a bad coil can cause this, especially after it warms up. But so can a condenser. Check the plugs, point gap, condenser, timing and lower plate wire first.

Re: Bad Coil?
 

Yes, definitely could be a failing coil. Most will start a car but after reaching running temperatures, they break down, example, mis-firing.

I'm lazy, two screws to replace a condenser or two screws & two wires to install your new coil. If you throw everything at the problem, you'll never clearly know what the issue was. Just me.

Re: Bad Coil?
 

I'm planning to replace one at a time just to see what fixes it. I wish I had a way to test the condenser & coil first.

Re: Bad Coil?
 

The lower plate wire can be effected by heat?

Re: Bad Coil?
 

These are my practices regarding condensers.

Re: Bad Coil?
 

I was assisting with a no start, he said I think it’s the coil, what do you think, after testing with a VOM I think it’s bad connections. He changed the coil, no start and put the original back, cleaned the connections at the battery and starter, she fired right up ! Not knowing what has been done ? start with the simple things K.I.S.S.

Re: Bad Coil?
 

It wouldn't hurt to have a spare coil,points and condenser. Easy to watch videos that I liked.Testing condenser. . . https://www.youtube.com/shorts/dGKRxY0Kt3w. .Testing the ignition system. . https://www.youtube.com/watch?v=oFmO...GHKiGM7w%3D%3D

Re: Bad Coil?
 

At lunch while digging through my new Model A parts stash that I have a new coil, condenser & points. Why I have them and never used them is beyond me. I'll try them one at a time to see what makes a difference. How long should coils last? I haven't changed the one on my '55 Chevy truck since.....the 80's....

Re: Bad Coil?
 

Coils can last many decades. Epoxy coils can fail due to excess heat. Many original Model A coils have failed due to the accumulation of heat damage. Oil-filled coils can leak, but generally hold up longer than epoxy coils.

Re: Bad Coil?
 

I replaced the coil on my fathers car in 2022 because a new one came with the new electronic ignition. I don't know how old the other one was but it was on the car in 1972 when my father brought it home from his parents place. I was 14,sadly I can't ask him about the car anymore but that was the year we begin working on it then paused after we had the engine rebuilt in Richmond ,they could do the babbit bearings , he drove it for a while but was to busy to keep driving it so it set. I picked it up again in 2019 when dad said wanted to drive it now at 84 if I could get it running,I did after four years and to much money in new parts . I thought new tires ,belts and hoses would fix it ,wrong everything on that car was shot.Dad had unhooked the front brakes because they made the car shake ,worn out.Then he drove it a few more times and was happy until I took his keys away,he could no longer drive.His dad bought it in 1951 for $100 when he was 16.

Re: Bad Coil?
 

Hello, condensers are a known issue on Model As , old timers used to keep a few under the seat , and some of the replacement ones aren’t that good, the first place I look if having power lost problem. Good luck.

Re: Bad Coil?
 

Don't forget the coil wire. If it's a carbon one they will fail.

Re: Bad Coil?
 

Interesting, Thanks Wick. jb

Re: Bad Coil?
 

And?

Re: Bad Coil?
 

Turns out I have been running my V8 Coil for 20 years wired wrong. I was wondering my '33 was giving me trouble. Instead of having it wired correctly, I was running the car sending 6 volts continuously to the coil and slowly burning them out, blaming the coil instead of the correct wiring path.

Solution: methodically check and verify the wiring first before replacing every related component. Car runs great now.

Re: Bad Coil?
 

FourFords and others, the necessity to check your coil wiring with a polarity tester. It will run, but not with the same Viagra.