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Old 06-30-2011, 12:52 AM   #1
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Default Carb problems?

I have a 78 Ford F-150 Lariat, Automatic, 8 cylynder. I have a question. When I step on the gas the truck bogs down. This happens if I stomp the gas or if I ease on it. It bogs down for a few seconds and then "catches" and then takes off. I am thinking it is a carb problem. I don't know much about carbs, ie. adjusting them, cleaning them etc. My question is, What would cause the bogging down and how do I fix it. Thanks in adavance


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Old 06-30-2011, 10:57 PM   #2
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Old 07-01-2011, 11:45 AM   #3
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it wouldn't hurt to rebuild the carb, you could have a accelerator pump leak or something else in the carb that needs replaced.
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Old 07-01-2011, 06:11 PM   #4
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Definately rebuild the carb, the kits give pretty good instructions on the basic disassembly and assembly. The choke linkage adjustments are confusing, you might consider not going there. The accelerator pump is remove and replace with an illustrated parts list for identification. The power valve (under float bowl) is not to be over torgued, snug plus just a little. The adjusting needles as described in the instructions, should be closed slightly counting and recording the turns, and then removed, reinstall is reverse, close slightly and back off to what was recorded prior.

With engine back running, set idle to spec, turn each mixture adj needle in slightly to gain max RPM and back off 1/8 turn. Reset idle speed and go again with the needles. Be patient, and do this two or three times.
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Old 07-05-2011, 07:12 AM   #5
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I had a similar carb problem earlier that I solved with this thread:

http://www.f150forum.com/f13/1979-st...problem-85969/

You'll see a YouTube video there showing the disassembly of a carb, the one I have, and it might be the same you have as well.

Once I purchased the rebuild kit and took apart and reassembled my carb while following the video I realized how easy it was to do, so don't be intimidated.

But to start, do what Good Old Bill suggested and try adjusting all the mixture screws on your carb. I'll walk you through it in a little more detail, assuming your carb is fairly similar to mine. I have a 79 150 auto 8 cylinder as well.


That video talks in detail about the individual parts of the carb, how they work together and how it can be adjusted.

On the right side of the carb you'll see a long wire coming from the cab and attaching itself to a lever on the carb. There will be a screw there that can be adjusted; that's your idle speed. That can be adjusted in and out, you'll hear the difference. On the front of the carb, on the underside, there will be a screw on the left and one on the right (for a 2 barrel carb). These are your fuel/air mixture screws. Turn one in until the engine starts to stumble, then back it out a bit. Do the same to the other side. All of these adjustments need to be made with the engine running. You'll hear when your engine sounds good and when it doesn't. Experiment with it.

There are other adjustments that can be made but try these two first and see if that helps. You should rebuild the carb anyway and everything will need to be readjusted after anyway.
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Old 07-05-2011, 07:12 AM
 
 
 
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