Weird running problem...
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Junior User
Joined: Jan 2006
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Weird running problem...
I got my truck running pretty well for use around the farm. Took it out for a road test the other day and ran into a problem. The truck is an 82 f250 with 400 CI engine. The truck starts right up, idles well and takes off just fine. On the road though, once it gets up to speed...say 45 or 50 for about 30 seconds it starts to backfire out the exhaust and totally looses power. I have to pull over and let it idle for a few minutes then it will go again. It does this over and over again. It seems like it's starving for fuel, but would this cause a backfire? That sounds like a rich condition to me. I'm wondering if the EGR could be causing this problem...just an idea. Any help would be great.
Tim
Tim
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
A number of things can cause this problem:
bad ignition module
carb icing
restricted fuel lines
bad fuel tank vents
cracked fuel lines
clogged fuel filter
weak fuel pump
etc
The EGR will usually cause an idle problem, pinging, or a continuous power problem.
bad ignition module
carb icing
restricted fuel lines
bad fuel tank vents
cracked fuel lines
clogged fuel filter
weak fuel pump
etc
The EGR will usually cause an idle problem, pinging, or a continuous power problem.
Thread Starter
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Junior User
Joined: Jan 2006
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Well, the fuel syetem is brand new with exception of the tanks themselves. Lines, pump, filter and carb rebuild has all been done within the last year. The only thing that might be an issue is if there is crud in the fuel tanks clogging the filter. The truck did sit for a long time. If that was the case though, i'm not sure why the problem would come and go. How can you tell if the carb is icing? Would it come and go that quickly?
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Excess fuel pump pressure could be overpowering the carb inlet valve. The fuel pump pressure is determined by a spring in the pump. Many pump rebuilders do not check every spring that they put into a rebuilt pump, so you can get a pump with too much pressure at higher RPM.
Check your plugs, look for indication of a rich mixture after driving at 50 MPH.
Check your fuel pressure when you rev the motor. It should be about 5 psi.
Check your plugs, look for indication of a rich mixture after driving at 50 MPH.
Check your fuel pressure when you rev the motor. It should be about 5 psi.
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