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  #1  
Old 07-11-2011, 11:55 AM
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79 F100 will not start, Did my Coil Fail Me??

Alright my 79 will not start. It will not do anything when i turn the key. I turn the key and nothing, by nothing i mean nothing, the only thing that lights up when i turn the key is the "brake" light.

Some history on the truck. When i bought the truck the coil was not hooked up the ignition switch, it was wired direct to battery on a togle switch. The coil is a factory coil. I turned on the truck many times and have left it running for up to 20 minutes at a time while i worked on it, the coild still running straight off battery.

The battery is charged, i have chaged the voltage regulator and the starter solenoid.

So finally i decided to wire the coil to the ignitoin switch. I ran the green/red wire to the + side of the coil. Success!! the truck starts with the key now.

Yesterday i pulled the truck out of the garage and parked it to begin my work. When i went to start it again, it did not want to start, but did turn over. Finally it cut on, then i worked, then i shut it off. well when i was done, i tried to start it again and nothing. Doesnt even turn over. No click no nothing. All the lights work, so the battery is charged. It had done the hard starting on other occasions. Was this a sign of the coil failing?

Did i fry my coil by running it straight to the battery? I hope i did cause its not an expensive fix if it is. What do yall think?

Also, did i do good in wiring the green/red wire to the + side of coil? The truck started from the ignition when i did. What is the green/yellow wire for? that one is not hooked up.

Any help or thought is much appreciated. Thank you.
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  #2  
Old 07-11-2011, 07:28 PM
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A stock Ford coil of this era cannot be connected straight to the battery. The factory coil is powered through a ballast resistor so that the voltage stays around 7 to 9 volts when running. Running a full 12+ volts to the coil will overheat the primary winding, which can cause the coil to fail prematurely.

The engine not even turning over is a different story. The engine should be able to turn over all day long (exaggeration) even if the coil is completely gone. If you're not even hearing a click, then pull the wire off the 'S' post of the solenoid and verify that it's receiving 12 volts with the key in the START position.

When you say green/yellow, do you mean it's greenish-yellow, or green with a yellow stripe, etc?
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Old 07-11-2011, 10:24 PM
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This distributor is not the original. The guy before me did the 460 swap and threw in an older distributor and did a quick wiring just to hear it run. So that how i had it while i was messing with it.

To test for full voltage, do i need to crank the truck or just have the key in that position with the meter on the "S" post? I will buy a new coil just in case. If it is not getting 12V, what could be the problem? The solenoid is only like 2 months old.

Green with yellow stripe that runs to the coil. The thing is that the coil was not hooked up when i bought the truck. I cut the cap off and hooked up the green/red wire to the + side to be able to start the truck. I didnt connect the green/yellow wire.
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Old 07-12-2011, 07:47 AM
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To make sure the solenoid is getting power, remove the wire off the 'S' post and check for voltage coming from the wire boot while a helper keeps the key in the START position (same as if you were trying to crank it over). This is to make sure that the solenoid is even getting the signal in the first place.

Do you have anything coming from the negative terminal of your coil, and if so where does it go?
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Old 07-12-2011, 08:18 AM
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Ok, I will try that tonight.

The only thing going to the - side of the coil is the distributor. Like i said, the guy who had it before me just wanted to hear it run so he threw an older style set up in there.
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Old 07-12-2011, 07:38 PM
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If this truck has Duraspark electronic ignition that would have been correct for the year, then the (-) side of the coil should go up to the Duraspark box. The only application where the (-) side of the coil should go straight to the distributor is with points. Does this have points, or electronic?
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Old 07-13-2011, 02:14 PM
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Hello,

My truck is a 79 and it has all the duraspark stuff still there. But in order to make the motor run, the guy put a points set up in there. So thats why the coild was jsut wired to the battery and the only thing on the - side it the distributor. This set up is fine for now and im not sure if i want to go back to the duraspark box. I am thinkgin of doing an HEI conversion later.
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Old 07-13-2011, 02:23 PM
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HEI is gm ! dura spark is 1 of the best ign. systems ever. you have 12v system and point & coil system requires only 8v to coil ! w/out a ballast resistor, u burned out coil/points ! go back to electronic dura spark, u will never have a problem again ! well, never say never, lol
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Old 07-13-2011, 04:22 PM
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Yeah HEI is GM, but its not a bad set up and there are a couple of people who have done it and are happy with it. Plus its only like a one wire hook up and your done. There is nothing to really worry about unless it completely craps out. I have heard that the duraspark will go out and not cut the truck back on. My HEI conversion is just a thought for now. I am going to run the current set up while i get the truck back on the road and running like it should.
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Old 07-13-2011, 04:22 PM
 
 
 
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