77 F350 Ignition Module Problem??
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Junior User
Joined: Apr 2005
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From: Central Texas
77 F350 Ignition Module Problem??
HELP!!!!
I have a 77 F350 with a 460. In the last two months my truck has died, usually after running for about 15 minutes, but not always. When it does die, it will suddenly cut off, and sometimes would start right back up. I have replaced the Motorcraft ignition module twice and recently put one in from Autozone. After a month of problem free driving, it died on me again today. I popped the hood and let it cool for about 5 minutes and it fired back up. The module was very hot to the touch, but we have been having 100 degree plus temperatures here in Texas.
Autozone tested the module and said it passed. When I re-installed the module, I put four washers (about 1/4 inch total space) between the module and the inner fender. Drove home without a problem..but my confidence is dwindling!
Any other ideas on what could be causing this and how to fix it???
Thanks, John
I have a 77 F350 with a 460. In the last two months my truck has died, usually after running for about 15 minutes, but not always. When it does die, it will suddenly cut off, and sometimes would start right back up. I have replaced the Motorcraft ignition module twice and recently put one in from Autozone. After a month of problem free driving, it died on me again today. I popped the hood and let it cool for about 5 minutes and it fired back up. The module was very hot to the touch, but we have been having 100 degree plus temperatures here in Texas.
Autozone tested the module and said it passed. When I re-installed the module, I put four washers (about 1/4 inch total space) between the module and the inner fender. Drove home without a problem..but my confidence is dwindling!
Any other ideas on what could be causing this and how to fix it???
Thanks, John
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From: Virginia
With the engine running, take a voltmeter and put the positive lead on the coil + and the negative lead on the engine block. See what the voltage is. If it's 12 volts, then someone has re-wired the ignition and bypassed the resistor, which may cause the module and the coil to overheat.
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Junior User
Joined: Apr 2005
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From: Central Texas
Thanks Dave, I will check on that. A friend asked me a good question, my truck has the dual battery set-up, would Ford have made a different ignition module for these trucks with a higher output alternator? Just wondering if that would play any part in this.
Thanks, John
Thanks, John
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Junior User
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From: Central Texas
Ok, checked the coil, with the engine running, got 10.5 volts. I have the wiring schematics and checked all the under hood ignition wiring, found no blown fusable links and everything appeared to be intact, routed and attached as expected. Today, I changed the distributor to eliminate that. New parts so far: the coil, distributor and the third ignition module.
Any thing else I should look for?
Thanks, John
Any thing else I should look for?
Thanks, John
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From: Virginia
Ok, the voltage sounds good. Maybe we had better take a step back and see if it's a fuel problem. The next time it happens, jump out and take the aircleaner off. You will have to climb up and lean over the carb, and while looking down the carb throat, push the throttle back with your hand. You should see two strong streams of gas flowing into the engine when you push the throttle back.
If you get little dribbles or nothing at all, you may have a fuel vapor lock problem. I had a similar problem with a 53 f100 I built, and I had to move the fuel line on the other side of the frame rail. It was about 3 or 4 inches from the header, but I guess the radiant heat would get the line too hot. It would only do it in town.
I do know Ford must have had problems with their trucks with 460's in the mid eighties. Those trucks had a low pressure electric fuel pump in the tank, and a special fitting at the carb that let some of the fuel come back to the tank. This kept the fuel moving and kept it from the getting to hot in the line. I don't know if your truck is supposed to have this system or not.
If you get little dribbles or nothing at all, you may have a fuel vapor lock problem. I had a similar problem with a 53 f100 I built, and I had to move the fuel line on the other side of the frame rail. It was about 3 or 4 inches from the header, but I guess the radiant heat would get the line too hot. It would only do it in town.
I do know Ford must have had problems with their trucks with 460's in the mid eighties. Those trucks had a low pressure electric fuel pump in the tank, and a special fitting at the carb that let some of the fuel come back to the tank. This kept the fuel moving and kept it from the getting to hot in the line. I don't know if your truck is supposed to have this system or not.
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From: Central Texas
That was my initial thought also. When this problem first surfaced, a friend of mine kept telling me he thought it was the module, but I was convinced it was a fuel system problem. I re-located the fuel line from the pump, away from the engine block, and into the carb. I also thought I might be getting trash into the carb from the in-cab tank, so I installed another fuel filter. That, unfortunately, did not fix my problem. I also rebuilt another carb and ran it, with the same results.
A long time Ford mechanic is scratching his head with us! He said that the only two things he saw fry the Motorcraft modules was heat and old age (he said that it was not uncommon to get 70,000 - 100,000 miles out of the factory modules). Unless I am having an incredible run of bad luck on modules, I'm at a loss to figure this one out...
I've toyed with the idea of re-locating the module inside the cab to see if that does anything??
Thanks, John
A long time Ford mechanic is scratching his head with us! He said that the only two things he saw fry the Motorcraft modules was heat and old age (he said that it was not uncommon to get 70,000 - 100,000 miles out of the factory modules). Unless I am having an incredible run of bad luck on modules, I'm at a loss to figure this one out...
I've toyed with the idea of re-locating the module inside the cab to see if that does anything??
Thanks, John
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From: Virginia
It sounds like you changed a lot of stuff with the fuel system, but have you really checked for fuel right after it has quit on you just to make sure?
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Junior User
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From: Central Texas
Not the way you describe. The extra fuel filter I put in is clear and close to the carb. I never saw any fuel bubbling inside the filter, but, if it happens to me again (knock on wood!) I will check inside the carb.
Thanks, John
Thanks, John