Wont run

Tiny
GATOR959865
  • MEMBER
  • 1984 FORD F-250
  • 5.6L
  • V8
  • 4WD
  • MANUAL
  • 285,000 MILES
I was backing up in a parking spot and the truck shut off just as if you turned the key off. Would not start at all. Got it started by pushing it off as its a manual. It ran for about a minute then shut off again. We've replaced the solenoid the ignition coil and the brain box. Still wont start. It started and ran after the ignition coil was replaced for about thirty minutes. I have no clue what else it could be.
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Friday, August 5th, 2016 AT 8:14 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
Failing pickup coil in the distributor is the most likely suspect. The wires to it flex as the timing advances and eventually they break.
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Friday, August 5th, 2016 AT 8:31 PM
Tiny
GATOR959865
  • MEMBER
We changed the whole distributor and it still wont start.
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Saturday, August 6th, 2016 AT 3:45 PM
Tiny
CARADIODOC
  • EXPERT
Now hold on a minute. You said it started by push-starting it. That means you have a cranking problem. You also said you replaced parts in the ignition system, which means you had no spark. So do we have a "no crank" no start or a "cranks but wont run" no start? We have to decide if we are working on a cranking system or an ignition system problem.

One thing that can be related to both systems is the charging system. A failure there will result in the battery running down with slow cranking, and can cause the engine to stall. I think the place I would start is by testing the charging system. You can do the first part yourself with an inexpensive digital voltmeter. Measure the battery voltage with the engine off. If it is good and fully-charged, it will be 12.6 volts. If you find it is closer to 12.2 volts, it is good but discharged.

Next, measure the battery voltage again with the engine running. It must be between 13.75 and 14.75 volts. If it is low, suspect the generator or voltage regulator. If it is okay, that means it is okay to perform the second half of the tests, but that requires a professional load tester. Your mechanic will measure full-load output current and "ripple" voltage. Those will tell if one of the internal diodes is defective. With a bad diode, you will only be able to get exactly one third of the generator's rated output current. That is not enough to run the entire electrical system under all conditions. The battery will have to make up the difference until it slowly runs down over days or weeks.
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Sunday, August 7th, 2016 AT 7:45 PM

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