Does anyone have a great answer why my 75 F150 460 would just die after running for an hour or so. I've replaced the EI module twice, new distributor, new coil, new cap & rotor, new plugs & wires, new key switch, rebuilt carb, new battery, alternator checked and good. It runs great for about an hour or so then dies like someone turned the key off. Let it sit a while and it'll start back up but sometimes cranking it over and over will get it to go too. One other strange thing-it acts like it wants to start as soon as I let the ignition key go from start to on-otherwise it acts like its not getting any spark in the start position (only does this if its been running for a while). Whatever it is, its not consistant. Runs for an hour or so then quits (without sputter), sometimes it'll restart right away and run for a while but then quit again, sometimes it won't start again until it another day--then starts up no problem!! I've even gone as far as putting a fan on the EI module! I see from other threads that this is a rather common problem. It sounds like a module problem but there has been 3 modules in there and NAPA says the two I have left are good. I'm thinking about replacing the wiring between the module and the distributor & coil next. Can anyone make sense of this??? Also, could that ballast in there have anything to do with it??? I've also been reading that it might be a fuel problem (clogged filter, canister, pump)??? Really appreciate some help with this one!!

 

When my ingnition switch went bad it did the same thing. I also
encountered the EI problem(just quits).....but when my switch went bad several years later it did the same thing. What I had to do before replacing was turn the key to start then back it off to the left just a hair. For 25 dolars it was a worth replacing(got it from LMC).

 

My F-150 has never had this problem, but I have a Jeep Grand Wagoneer with the Duraspark II that has eaten a bunch of Ignition Modules and did this same thing as yours. Other things I have heard that cause a similar problem as this are the ignition switch as mentioned above and the magnetic pickup in the distributor.

BTW, in the Jeep I replaced the Duraspark box with a Jacobs MileageMaster and haven't had a problem since.

 

Does your truck have a catalytic converter? If so, and if it's original then it's got about 30 years of build up inside. That might explain why it shuts off after an hour or so and you sometimes can't start it until the next day (probably getting cherry red and taking several hours to cool off enough to let exhaust through).

Dave

 

Well, I tried replacing the ignition switch and that didn't seem to help. I might just replace the whole ignition system. Its got no catalytic converter but thanks for the help

 

You need topull a plug wire to see if its getting any spark.

Take the air cleaner off and see if its getting fuel.
If its not getting spark, I had one with a simular problem it turned out that for some reason the big yellow wire leading into the ignition switch was dead. rather than chasing it down I ran a new wire to the switch.
Maby a pin hole in the fuel line some where.

 

Does your truck have a Duraspark II or the Ford breakerless ignition? The Duraspark II has a blue grommet on the module with one 4 wire pigtail and one two wire pigtail.The breakerless module has a green module,if I'm not mistaken with one four wire pigtail and one three wire pigtail.
If your truck has Duraspark II and no spark,probe the white wire going into the module.It should have power when cranking.The positive side of the coil should have power with the key on and while cranking.You can also probe the negative side of the coil while cranking-the test light should flash.

 

When you say that the vehicle won't start, does the engine even turn over and just spins and spins by the starter?

Or
When you try to start, it just clicks or nothing at all and the engine won't even spin?

If the engine spins by the starter, do you have sparks from the coil and all of the spark plug wires?

Is this a Carb or fuel injector, throttle body injector? Fuel injectors usually have this problem with their relays going bad.

What about your timing?
Camshaft gears usually wears out and the timing chain will be slack.

For V8 engines; to test for timing chain, remove the distributor cap, turn the crankshaft to the 0 degree TDC. I usually use turn the crankshaft using the large bolt on the crankshaft itself. Once you got the 0 degree TDC, turn the crankshaft counter-clockwise to 30 degree BDC, then slowly turn the crankshaft clockwise to 0 degree TDC. (Make sure you don't past the 0 degree TDC otherwise you will start from the beginning.) Next, watch the distributor rotor and turn the crankshaft slowly counter-clockwise. Once the rotor starts moving then stop turning the crankshaft. Look at the timing pointer. If the timing pointer points past 5 degree BDC then then timing chain is loose because the camshaft gear is worn out.

 

I had the same EXACT problem w/my truck, I asked and asked and tried everything that was mentioned above and some that weren't. What fixed my problem...I took a ground from the battery and ran it straight to where the ignition box case bolts to the fender well. Supposedly from what the guys say here that the case doesn't need to be grounded at all, but the second I did that I had no more problems. An old Ford fanatic of my Dad's told me to do it, I did, and well the truck hasn't died once since. I'm not saying it's the right way to fix your problem...but it's worth a try, it worked for me and there's nothing unsafe about it. Let us know how it turns out for you.

 

I actually had a IH scout that did the same thing and it was a poor ground from the battery box as well.