Electical Problem? Wiring Harness?
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4wd High
Joined: Mar 2003
Posts: 9
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From: Ohio
Electical Problem? Wiring Harness?
I have a strong running '78 F-250. Occasionally though I have a problem that I can't find the root cause for. The truck normally starts right up on one click and runs great. There are times though that I am crusing along and I can feel it lose spark just for a second or two. Other times it will stall while I am on the throttle and rolling- just like I had turned off the key. I can throw it in neutral and it will usually start right back up like nothing happened and I keep driving. Lastly, sometimes it won't start, it will turn over like it has no spark at all so I stop, come out 10 minutes later and it will start on first click. I have replaced my battery (since it was time anyway), positive and negative battery cables, coil and coil wires, cleaned grounds to bare metal, and cleaned up all connections to the solenoid and alternator. Any other wire connection under the hood I could find I took apart, cleaned up, and put back together with dielectric grease. Is it my wiring harness? How do I check it, and then where is a good place to get one? Thanks for your time people...
Posting Guru
Joined: Dec 2003
Posts: 1,205
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From: Ontario
Sounds like it's your ignition box
On the fender, they sometimes stop working completely but many many times are intermittent in their operation which can be dangerous so being as they are so cheap to replace go ahead and do it just make very sure you replace it with the correct one, also make sure the one you have now is the right one to start with.
Or it may just be corrosion in the plug or plugs that attach to the box.
Also there is a special high altitude one I believe it has something to do with advancing the timing if I remember correctly.
Rick.
Or it may just be corrosion in the plug or plugs that attach to the box.
Also there is a special high altitude one I believe it has something to do with advancing the timing if I remember correctly.
Rick.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
100% agreed on the module or pick-up. There are tests you can run on these, but unfortunately the symptoms are usually brought on by heat, so if you're parked in your driveway after the motor has cooled off or you take the module into the parts store to be bench tested, it won't show any problems.
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I'll add that years ago my truck started doing that. It didn't matter what the temperature was, I could have just started the truck for the first time that day and after 45 seconds just shut off. But it would instantly start right back up once you hit the key.
Or it would die going down the road, shift into neutral like you said, hit the key and start right back up.
What I ended up doing was I got some spare inner fenders from the junkyard which still had a module mounted on it. Put that one on my truck and the syptoms seemingly went away, only to return maybe 2 years later. Swapped back to my original module, but replaced the pick-up in the distributor and done deal.
It's pain in the butt a little, but oh well.
I do notice the parts store have quite the range of prices for either the module or pick-up. So I suppose buyer beware.
Or it would die going down the road, shift into neutral like you said, hit the key and start right back up.
What I ended up doing was I got some spare inner fenders from the junkyard which still had a module mounted on it. Put that one on my truck and the syptoms seemingly went away, only to return maybe 2 years later. Swapped back to my original module, but replaced the pick-up in the distributor and done deal.
It's pain in the butt a little, but oh well.
I do notice the parts store have quite the range of prices for either the module or pick-up. So I suppose buyer beware.
Senior User
Joined: Nov 2007
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Should be able to pick up the ignition module in the JY for a cheap test. Just make sure to look at yours where the wires go into the box and note what color the plastic is. I think there is a blue kind and a yellow kind.
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Not sure of the exact differences, but some are California and others are hi-altitude.
Josh
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Posting Guru
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My '76 Crew Cab (460) used to do the same thing. As a matter of fact, this is the reason it was for sale when I bought it. I had owned it nearly a year when I finally discovered the cause: where the wiring harness comes up over the back of the bellhousing and runs along the intake manifold check VERY CLOSELY that there isn't a very small break in the insulation. Mine had a worn spot so small I could hardly see it, but when it got against the manifold it would kill the engine.
As for modules, you can get them at any NAPA store, or at least you could less than a year ago. I had to buy a new one for my '79 when mice chewed the wires off it.
As for modules, you can get them at any NAPA store, or at least you could less than a year ago. I had to buy a new one for my '79 when mice chewed the wires off it.
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4wd High
Joined: Mar 2003
Posts: 9
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From: Ohio
Hit the nail on the head.
You guys were right. I am back on the road with a new module. Haven't had the same problem and I got it good and hot on a 52 degree day and it never flinched. I have my confidence in her back, Thanks!
where can i pick up
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