Bucking after warm-up???
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Joined: May 2010
Posts: 350
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From: Spartanburg, SC
Bucking after warm-up???
I have a 1986 F150 300, 4 speed 4x4 that has been converted to a Duraspark II ignition system. When I did it, I replaced the carb with a new Carter 1 barrel.
This past weekend I did a fuel tank replacement and also replaced the fuel pump and the sending unit. I started driving the truck this week and on my way to work this morning and on my way home this afternoon, the truck started bucking after it was warmed up. On the way home, it got so bad, I didn't think I was going to make it. It is especially bad on acceleration so I'm not sure what is going on. If it were the fuel filter, why would it wait to happen after warm-up?
It was cold this afternoon when I got in the truck and it ran great for the first 10 minutes, then the bucking started. It got worse the closer I got to the house.
Any ideas?
This past weekend I did a fuel tank replacement and also replaced the fuel pump and the sending unit. I started driving the truck this week and on my way to work this morning and on my way home this afternoon, the truck started bucking after it was warmed up. On the way home, it got so bad, I didn't think I was going to make it. It is especially bad on acceleration so I'm not sure what is going on. If it were the fuel filter, why would it wait to happen after warm-up?
It was cold this afternoon when I got in the truck and it ran great for the first 10 minutes, then the bucking started. It got worse the closer I got to the house.
Any ideas?
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Joined: Dec 2007
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From: Boise, Idaho
My first guess would be the ignition module. On the duraspark system, there aren't any components that tie into the engine heat, such as with an EFI (or the feedback) that have signals from the temperature gauge.
However, the ignition module gets hot after a while, and if they're faulty, this heat'll cause them to start fizzling out until they cool back down.
I'm not 100% sure how to check for this since they'll most likely be cool in the store if you were to have one tested.
However, the ignition module gets hot after a while, and if they're faulty, this heat'll cause them to start fizzling out until they cool back down.
I'm not 100% sure how to check for this since they'll most likely be cool in the store if you were to have one tested.
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Senior User
Joined: May 2010
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From: Spartanburg, SC
The one I have is an old one I purchased out of the junk yard. Funny thing is it ran fine prior to the tank replacement. I just ran out and drove around the block for 30 minutes with no issue.
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Senior User
Joined: May 2010
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From: Spartanburg, SC
Looking at the Rock Auto website, I am seeing an ignition module for an 80 model, part number LX203 for $29.79 but I also see part number LX203X for $48.99. Anyone know the difference? At that price, I may go ahead and get a new one. The one I have I pulled off of a 1976.
Post Fiend
Joined: Dec 2007
Posts: 8,521
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From: Lost
Blocked vent. The tank cannot get air in to replace the fuel being drawn out, so it creates a vacuum effect. Try loosening the fuel cap and drive it. If the issue goes away, tighten the cap. If it comes back, there's your answer.
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Joined: Dec 2007
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From: Boise, Idaho
Hrmm... I thought that, but I struggled with that issue for a while and couldn't seem to get rid of it. But when it would happen, it'd usually be after a few hours of driving, and then poof, dead. It wouldn't drive, start, or anything, and there was no fuel from the engine to the fuel tank (dry line).
Hopefully that's it though, since it'd be an easier fix.
Hopefully that's it though, since it'd be an easier fix.
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Senior User
Joined: May 2010
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From: Spartanburg, SC
Interestingly enough, I had no issues driving to work today. I'm thinking it had to be the vent because the tank was very full yesterday and I'm down to 3/4's today so probably enough room for air in the tank to not give me any issues.
Thanks guys, Thanks Rogue, good catch!
Thanks guys, Thanks Rogue, good catch!
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