Electrical woes
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Elder User
Joined: Jan 2004
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From: Eastern Pa
Electrical woes
1979 F150 with duraspark. I've done some other testing and here is what I've found. It won't start now. There is power to the + side of the coil. If I put a test light on the dist side of the coil while cranking there is nothing coming out there. If unplug the dist plug and check for power at the dist side of the coil there is none. I swapped out a coil and it did the same thing. I continue to get the brief fire as I turn the key off. Danlee said that is the coil firing as the circuit is breaking and I guess that makes sense. I can read a wiring diagram just enough to get in trouble. Are there any of the wires either from the control box or anywhere else that I could check for continuity that would tell me where the problem lies? Is the greeen/yellow wire on the dist side of the coil a key to this? Any more suggestions would be appreciated. I have replaced the pickup coil, control box and ignition switch. Some times it starts and goes for a mile or so and dies and won't restart. Sometimes it will cold start, sometimes it won't.
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Joined: Jan 2001
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From: Virginia
Do you have voltage on the red wire going to the control module on the fender? Also, check the black wire coming from the dist. Check for continuity from the black wire to the engine block ground. This black wire is tied to ground inside the dist, and is the ground for the whole system.
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Elder User
Joined: Jan 2004
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From: Eastern Pa
Ok I do have power in the red wire going to the control box. I have 3 wires in the harness from the distributor. Ther is a black one with a white stripe, an orange one and a purple. If I disconnect everything from the - side of the coil I get about 9-9.5 volts when cranking. How would I check for the proper ground from the dist.?
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Joined: Jan 2001
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From: Virginia
Put your meter on rx1 scale. Touch the meter leads together. You should get close to zero. Then take one meter lead and put it on the engine block metal. Then put the other lead on the black wire shown in the diagram above(I think you said yours was black/white). You should get a reading close to zero.
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Joined: Jan 2001
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From: Virginia
Here is some more test procedures if you want to try them.
http://www.autozone.com/servlet/UiBr...3d800a506e.jsp
You may have to start messing around with the plugs, making sure they are making good contact with each other.
Also, take the dist cap off and wiggle the rotor around. If the dist bushings have too much play, it may be messing up your pickup.
http://www.autozone.com/servlet/UiBr...3d800a506e.jsp
You may have to start messing around with the plugs, making sure they are making good contact with each other.
Also, take the dist cap off and wiggle the rotor around. If the dist bushings have too much play, it may be messing up your pickup.
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Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
Well after lots of testing and following many of your advice I decided to take the pickup coil back to Autozone. They said they could check the module. When I got there they all said "who told you we can check the module?" Well they looked up a thing or two and found some instructions on their computer and all they did was use an ohm meter to check resistance through the module. It should have read between 400 and 600 and it read nothing. They pulled out a new one and checked it and it registered about 460, so I brought the new one home and voila, it works. I only hope it keeps working now. I wonder if other manufacturers check theirs in a similar manner. Thanks for your help.
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