Ignition coil problems
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Mountain Pass
Joined: May 2014
Posts: 177
Likes: 1
From: Texas
Ignition coil problems
Ok I've posted a few times on here with ignition problems and have been getting a lot of help. Hopefully someone can help me with this too!
I just rewired my 1975 F250. Everything works except the ignition. When I crank it to start, it fires but as soon as I let off the starter, the ignition stops firing and it instantly dies. The wire going from the switch to the coil is getting extremely hot (smoking.) I was at first using a ballast resistor and then bought the resistor wire from NAPA. The truck will run with neither. It takes a matter of seconds for the resistor wire/ballast resistor to start smoking once I turn the key to RUN.
Is something wrong with the coil that is making it draw a ton of amperage? Is something else wrong?? Please help me!
I just rewired my 1975 F250. Everything works except the ignition. When I crank it to start, it fires but as soon as I let off the starter, the ignition stops firing and it instantly dies. The wire going from the switch to the coil is getting extremely hot (smoking.) I was at first using a ballast resistor and then bought the resistor wire from NAPA. The truck will run with neither. It takes a matter of seconds for the resistor wire/ballast resistor to start smoking once I turn the key to RUN.
Is something wrong with the coil that is making it draw a ton of amperage? Is something else wrong?? Please help me!
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
During crank, the coil gets full battery voltage... the resistance wire or ballast is out of the circuit. On run, the ballast is in the circuit. Sounds like there is a short on the "run" side. Suggest careful inspection of the ignition wiring, especially "run" side from coil back to the resistance wire. Look for chafed insulation or wiring "oops".
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Normally I would say the power wires to ignition module are swapped. (hot in "run" hot in "start". That will cause the cutting off when key is released But smoking wires suggests something else wrong. Aftermarket coil with too high a resistance is a possibility. Should be about 1.4 ohm primary and the ballast wire or resistor the same. Pickup coil in distributor should read 400-700 ohms across purple and orange with high resistance (7 meg ohms) from either to black wire. Diagram may help.
Freshman User
Joined: Nov 2014
Posts: 39
Likes: 0
From: Idaho
I was having a very similar problem. Got a lot of good advice here you can search my post history and find some answers. I suggest copy the diagram posted by gfw1985 and check the harness. Mine was melted across the top of the engine, between the distributor and the ignition box.
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