low voltage at coil primary
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low voltage at coil primary
hello-
1978 F150XL Ranger Supercab 351M running propane
i have gone through two coils in 6 months with stock Durasparkll. the coil primary is getting about 6.6 volts in "on" position, and about 4.5 at idle. this seems a little low to me, and would this cause a coil to go bad? what might be the cause of this? my alternator seems good.
Thanks!
1978 F150XL Ranger Supercab 351M running propane
i have gone through two coils in 6 months with stock Durasparkll. the coil primary is getting about 6.6 volts in "on" position, and about 4.5 at idle. this seems a little low to me, and would this cause a coil to go bad? what might be the cause of this? my alternator seems good.
Thanks!
Posting Guru
Joined: Feb 2004
Posts: 1,388
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From: Saratoga, NY
You might have a bad ballast resistor (wire). When you are cranking the engine you should get full batt voltage at the coil, so disconnect and ground the coil secondary to the block and crank the engine and see what volts you get. I'm not so sure low volts would kill a coil, but high volts could. Anybody ever have this problem?
Posting Legend
Joined: Sep 2001
Posts: 30,255
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If you look in a Chilton's service manual there is a whole series of tests to go thru to find the problems with these ignition system. The old book I have has pictures and a lot of info. I would suggest getting one of those manuals and performing the tests listed rather than guessing.
Posting Guru
Joined: May 2002
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From: Southwestern Michigan
Make sure all of your grounds are good...like the engine to body ground.
I once had a truck that was so rusty,it would run bad with the headlights on, I added a ground wire from the battery to the fender...and it fixed the problem.
I once had a truck that was so rusty,it would run bad with the headlights on, I added a ground wire from the battery to the fender...and it fixed the problem.
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