Odd stumble
06-26-2011
#21
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Join Date: Jan 2011
Location: Durham, NC
Posts: 646
Well, after 2 weeks and no problems, today that changed. I struggled to get the truck home. It fought me the whole way but I made it. It totally died in the shop and wouldn't restart. Then I noticed with the engine off and key in run, the tack was jumping around, and I noticed a arching sound from under the hood. I jumped out and tried to find it. It was coming from that area of the coil, rear left side. But stopped before I could find it. I suspect what ever was making that sound is the source of my problem. The the truck restarted and ran fine. I tapped all around and nothing happened. Any thoughts on what I should be checking here?
06-26-2011
#22
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
I plan to pull the coil off and inspect it tomorrow. Something is aching to ground and it's causing the tach needle to jump. I'm thinking there may be a crack. I may end up just replacing the coil.
06-27-2011
#23
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
I decided to replace the coil. I was driving back from the DVM and autozone was right there, so I stopped and picked one up.
I tested the secondaries on the new coil.
And tested the primaries.
Then I tested the primaries on the old coil.
And the secondaries on the old coil.
Hmm, wonder what is wrong?
I tested the secondaries on the new coil.
And tested the primaries.
Then I tested the primaries on the old coil.
And the secondaries on the old coil.
Hmm, wonder what is wrong?
06-27-2011
#24
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Join Date: Jan 2011
Location: Durham, NC
Posts: 646
I decided to replace the coil. I was driving back from the DVM and autozone was right there, so I stopped and picked one up.
I tested the secondaries on the new coil.
And tested the primaries.
Then I tested the primaries on the old coil.
And the secondaries on the old coil.
Hmm, wonder what is wrong?
I tested the secondaries on the new coil.
And tested the primaries.
Then I tested the primaries on the old coil.
And the secondaries on the old coil.
Hmm, wonder what is wrong?
Looks like the secondary is open.
Does it run now?
06-27-2011
#25
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
Yes, but it was running before, not sure how it could run with the secondaries open. I tested it several times, even used a file to clean up the metal and make a good connection. I would expect a open to not run at all.
06-27-2011
#26
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Join Date: Jan 2011
Location: Durham, NC
Posts: 646
The air gap where the secondary winding opened would act like another plug gap, similar to 2 plugs firing together in series, like Ford's EDIS. So it might run, but poorly due to reduced voltage to the plugs.
06-27-2011
#27
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
That's a possibility. Perhaps it had a very weak spark. Then from time to time dropped out all the way. All I can do now is drive the truck and see what happens. I thought for sure I found the problem being a loose plug on the fuel pump. Ran problem free for 2 weeks. Perhaps the arching I heard was inside the coil.
06-28-2011
#28
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
I tested the old coil wrong. I should have tested from tach terminal to the post. Testing that way I get about 7.70 ohms. When I heat the coil up it goes over 8.50 ohms. The new coil starts about the same place, 7,.70 ohms. When heated up I go to a bit under 8.10
06-29-2011
#29
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Join Date: Jan 2011
Location: Durham, NC
Posts: 646
The old coil sounds ok. A difference of 400milliohms is well withing the tolerances on the secondary winding resistance.
06-29-2011
#30
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Join Date: Jan 2011
Location: Sheboygan WI
Posts: 459
Ya, hard to say. But I really can't figure out why the ignition is kicking out. Something in that area was arching. There are a few plugs in that area, but I don't see any problems there. Only high energy I see is the coil. There may still be a crack in the old coil, I just can't say. If I ever get a chance I may have to put the old coil back on and start it up at night. Then mist the coil and look for any flashing.
