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engine running rough and backfiring

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New User

Feb 19, 2017, 10:28 AM

Post #1 of 4 (1751 views)
engine running rough and backfiring Sign In

have a 65 Chevrolet c10 pick up with a 265 v8. just replaced fuel pump and fuel filter. ran fine for a little while. started it after sitting a couple of weeks, ran rough started back firing and will not idle. almost like it jumped timing. not sure how to rule out carburetor problem or what

Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 19, 2017, 12:34 PM

Post #2 of 4 (1741 views)
Re: engine running rough and backfiring Sign In

Pleading IDK this engine by that displacement and how it's done with either of those parts. Not totally the point either but if fuel is now or before in the oil that's a problem or if fuel filter is right at carb could be a problem spot as well flooding out or debris making fuel keep running at needle valve when it should shut tight?

Still any could jump valve timing and should be checked that it didn't. Not GM that I knew of but some mechanical fuel pumps rode on a cam that was on and indexed to a cam gear I thought only Mopars did that. If so it might have disturbed something putting in fuel pump? Rule of thumb with mechanical fuel pump with contact on a cam any which way is to remove and replace on low area of the cam however it's done such that you don't force it back on by mounting bolts/nuts or can't without turning engine,


kev2 profile image

Feb 19, 2017, 1:08 PM

Post #3 of 4 (1732 views)
Re: engine running rough and backfiring Sign In

this is the first generation chevy small block, sister to a 283. and to amuse us it a chevy 4.3 V8?
I doubt it jumped timing sitting - and being babied - most likely fuel, the pump/filter solved the issue and then it reappeared so I would look at fuel quality- filters, inline and inlet "stone" at carb - maybe look in float bowl, crud and rust maybe.
Being an older model - check the dist remove cap - everything moving freely? spark at all 8?
Vacuum - there were not many vac accessories so that should be a easy check...

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 19, 2017, 1:32 PM

Post #4 of 4 (1726 views)
Re: engine running rough and backfiring Sign In

I would check fuel supply into a glass container. These mechanical fuel pump pull as opposed the electric pumps pushing. If any of the fuel lines between the pump and the tank get rotted, they usually don't leak fuel, the suck air when the pump tries to pull so check the condition of the fuel lines.

One way to test for this is to connect a 5 gallon gas can directly to the fuel pump with a fresh piece of hose and see if that cures the fuel supply problems.


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