Back-firing 300
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New User
Joined: Dec 2003
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my f-150
Can anyone help me out? I have an 81'f-150 with an inline six and its been backfiring every time i put a muffler on it.And also it just dies on me,it runs fine but it just quits after it dies it will start back up with no problem.I'm wondering if it might be electrical or not?
Posting Guru
Joined: Jan 2001
Posts: 2,357
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From: S. Mississippi
It sounds like when you add the muffler, its creating too much back presure for the engine to continue running normally. I'd check your catalytic converter, check your timing, and make sure you aren't running lean from a carb mis-adjustment.
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cat
I gutted the cat before it started back fireing.Friday i rebuilt the carb. and gave it a tune up.I guess I'll try another muffler.I've been using factory mufflers but I guess i'll try a glass pak..............THANKS FOR THE TIPS
Posting Guru
Joined: Jan 2001
Posts: 2,357
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From: S. Mississippi
How well does the truck run without the muffler on? if it runs decent without it, then there is a restriction somewhere that should not be there. If it runs fine without a muffler i'd look heavily at your exhaust, it could be that crappy flapper thing thats in the exhaust manifold, if it got stuck then that would indeed create too much back pressure.
Keep us updated.
Keep us updated.
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flappy thingy
Well my truck does not have that little flappy thing on it.I guess I'll have too replace the whole exhaust system.But on another note the darn thing is still dieing on me and i can't figure out why.I'm thinking electrical somewhere
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Fleet Mechanic
Joined: Aug 2002
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From: Swansea SC
BACK FIRE
Wolf try (if u have one) take the belt off for the air pump-my 1985 was doing this last summer and we took this off and no more back firing. Hope this helps TR (what a back fire she was making , louder than a shot gun)
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Senior User
Joined: Mar 2002
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From: PA
I have the same backfiring problem with my 1980 351M that is caused by the air pump. There is some anti-backfire valve there (I forget the real name of it) but after replacing it I still have the problem. I just take the belt off as mentioned in the post above. I put the belt on for it to pass emission inspection then take it back off.
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Joined: Mar 2004
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I had the same backing firing (leaning) and kept blowing muffers. There is an air pump bypass that works when decelerating, high vacuum to stop pumping air into the exhaust. Mine stuck open. Rather than replace the bypass valve I just took off the belt from the air pum. This completely stopped the exhaust pop.