1975 Ford F-250 Excellent Idle-Bogs/Backfires under Load

Tiny
SAGESUNRISE
  • MEMBER
  • 1975 FORD F-250
  • V8
  • 4WD
  • MANUAL
  • 150,000 MILES
My truck has a 390 w/electronic ignition and runs excellent. Went to start it and noticed it ran at an idle right when started (usually cold starting and you have to keep your foot on the gas for 15 mins before it will idle). Put it in drive and it bogged when I gave it gas-real bad! Reved it up but it would not clear up, acted like it wanted to die, but didn't. Let foot off gas, rpms back up to a perfect idle. Changed wires, fuel filter/pump. Was gunk in the pump filter. Now wondering if it might be the electronic ignition, cap, rotor, or carb needs rebuild? Any ideas folks? Like I said, it runs excellent at an idle. Wouldn't think it had any problems if you heard it run. One other symptom is that when you turn the key over, it seems like it turns over forever and won't fire up but as soon as you give up and let the key off, it starts right up. Every time! It also backfires really loud when you rev it up high (won't always rev up, though, and when it does, it still acts like somethings plugged up). Don't know what else to do. Thanks in advance for your help.
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Saturday, July 12th, 2008 AT 6:49 AM

2 Replies

Tiny
JACK42
  • MEMBER
Sounds like the carb needs to be rebuilt or at least cleaned out. If there was gunk in the pump filter, odds are good that the same gunk has found its way into the carb.
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Saturday, July 12th, 2008 AT 8:21 AM
Tiny
TALLAN1976
  • MEMBER
Did you check the timing? If it somehow got knocked out of time it will do this. Loosen your distributor a little and try moving it a little in either direction and see if it improves.
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Tuesday, September 9th, 2008 AT 5:27 PM

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