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I’m pretty sure the coil is the route of all my problems. There are no signs the oil leaked out and I can still hear fluid swishing around inside. I put a link to a video at the bottom, I know how much everyone likes pictures and videos. I plan on keeping the new ICM that I have, since they tend to go out. I will space it away from the mounting surface to allow more cooling effect. The truck still idled worse then before the backfire, but a half turn of the idle mixture screws, and vacuum is better and idle and smooth and quiet. MAYBE the O2 sensor is still good, we’ll see as I drive it to work the next few days. Thank you again to everyone who helped.
Coils are inexpensive and easy to swap. I wouldn't hurt to grab a spare regardless. I don't know that you should be hearing much swishing or sloshing, the coil should be mostly full and there shouldn't be too much sloshing of the oil inside.
Regarding spacers on the ICM, I don't think that is necessary but if you wanted to I guess you could. I'm thinking if I did it, I would use metal spacers to make sure the case of the ICM still has metal to metal contact with the body.
Coils are inexpensive and easy to swap. I wouldn't hurt to grab a spare regardless. I don't know that you should be hearing much swishing or sloshing, the coil should be mostly full and there shouldn't be too much sloshing of the oil inside.
Regarding spacers on the ICM, I don't think that is necessary but if you wanted to I guess you could. I'm thinking if I did it, I would use metal spacers to make sure the case of the ICM still has metal to metal contact with the body.
I didn’t even consider that, but it’s a great idea. I already purchased metal spacers from ace hardware cause they had the correct I.D. available in different lengths.
You can also add a ground wire to the fender well. Adding spacers moves it away from the fender well, more air flow should help to dissipate heat better.
Had the exact problem, for the first 20 minutes it ran flawless, then fell on it's face and most of the time would not re-start right away. Coil was getting too hot to touch. Purchased a new one and haven't looked back. Once it cooled off, I was back in business. Till it got hot again.
I drove about 30 miles with the new coil, perfection! The next day on the way to work: started faster and cold idled better than before. Half way to work, about 3 miles, started cutting out again. Cut out four times in total over the span of about three miles. After work, I changed the ICM in the parking lot. Cut out 6-7 times on the 5 miles drive home, WITH THE NEW ICM AND NEW COIL! After some looking around at home, I removed the coil plug and saw oil to the brim of the tower. So, engine off the volts at the wires is a little over 5. Engine running the volts are only 3.88! What the heck?! The coil has a sticker that says “12 volt” is that not what is suppose to be suppling it? By the way, the entire 6-7 minutes I’ve been typing this up, the engine has been idling in my driveway with ZERO issues. I’m starting to understand why mechanics hate electrical problems 😡
There is a resistance wire in the circuit to the coil. But it shouldn't drop the voltage that much. During start up the resistance wire is bypassed sending a full 12v to the coil with the white wire coming from ICM, when key goes back to run position the voltage to the coil is sent via the red wire, through either a ballast resistor or resistance wire built into the harness. The resistance should be 1.05-1.15 ohms across the ballast resistor (resistance wire). This reduces the voltage to coil when running to avoid overheating and prematurely wearing out the coil.
You could test that by checking resistance from red wire terminal on the harness side where it connects to the ICM and at the other end where it connects to the coil. There will be some resistance from the wiring harness itself, but you should not test much higher that the 1.05-1.15 range. It's possible that there is an issue with the resistance wire/ballast resistor in the circuit, such as a break in the wire, but there is still some contact allowing intermittent electrical current. When you're bouncing down the road it breaks the circuit causing your engine to cut out. Sitting idle in the driveway there is a lot less vibration.
I wanna make sure I get this right so I’m including photos. The red wire on the two wire ICM plug and the red wire(positive post) on the coil is where I’m testing resistance? I got a number WAY higher than 1 point anything … will y’all make sure I have the multimeter on the right setting and I have the probes in the right spots?
Looks like the correct setting on the multi-meter and you're showing about 80 ohms in that section of the harness. Per the Echlin Electronic Ignition Service Manual, the ballast resistor should be in the 1.05-1.15 range. Per the Ford shop manual it should be 1.10 right in the middle of that range. When in running condition you should have 6-8 volts at the positive side of the coil.
Given you have less than 4 volts and you are showing 80 ohms resistance, I would say you might have found the culprit. I am guessing there is a break or something going on in the wire between ICM and coil and it has been causing the intermittent issues. You could replace entire harness with a used one or make work an aftermarket harness such as what is offered through Painless or American Autowire.
The other option is get a ballast resistor with the proper rating, they are about the size of a Bic lighter and have a ceramic shell, they do get hot so you will want to mount someplace you don't have to worry about that. Remove the wire between the coil and ICM, replace with a new 14 gauge wire with the ballast resistor inline. Or build an entirely new harness yourself just reusing the ICM connections and the u-shaped connecter for the coil.
[QUOTE=mterickson;21391533]Looks like the correct setting on the multi-meter and you're showing about 80 ohms in that section of the harness. Per the Echlin Electronic Ignition Service Manual, the ballast resistor should be in the 1.05-1.15 range. Per the Ford shop manual it should be 1.10 right in the middle of that range. When in running condition you should have 6-8 volts at the positive side of the coil.
Given you have less than 4 volts and you are showing 80 ohms resistance, I would say you might have found the culprit. I am guessing there is a break or something going on in the wire between ICM and coil and it has been causing the intermittent issues. You could replace entire harness with a used one or make work an aftermarket harness such as what is offered through Painless or American Autowire.
The other option is get a ballast resistor with the proper rating, they are about the size of a Bic lighter and have a ceramic shell, they do get hot so you will want to mount someplace you don't have to worry about that. Remove the wire between the coil and ICM, replace with a new 14 gauge wire with the ballast resistor inline. Or build an entirely new harness yourself just reusing the ICM connections and the u-shaped connecter for the coil.
Does it matter that the key was in the off position? Can I put in a temporary wire to test if the voltage changed? The wires from the ICM plug go into the cab, what section of wire would I replace?
You can try the test again with the key in run and see what happens. I would disconnect the battery when you do though, at this point you're only checking continuity not voltage and you may get inaccurate test results with an energized system.
Now I know what the problem is, I want to replace the resistor wire. Problem is, I can only find two sources that list it for a 79 ford but they use the same picture and it doesn't look right and it’s $30! Can I use “regular” wire and put a ballast resistor inline or will that mess things up? Is there a newer/better option to drop voltage? I’m fine with custom wiring. I ask because every time I see David Freiburger having ignition issues, it’s the ballast resistor. Do I even NEED a resistor? I read it needs a lower voltage to not destroy the points. Sorry for the ignorance, are the points the internal parts of the distributor?
Ford resistor wire, $30 is about as cheap as you'll find. I did it on my 66 Fairlane. It was easier to replace for me than build a like scenerio. Yes you need it for your current configuration.
