Backfiring through carb. Wont start

[chief_shotts]

This morning i go to start my truck and it turns over but wont start. After a couple tries it backfires through the carb (Holley sniper efi). A couple small flames i promptly put out with a rag. Ive never experienced this particular problem. Does anyone have any suggestions.

Also want to note that i pulled a few plugs and they were soaked with fuel.

Engine is a 383 sbc with holley sniper efi 1.

 

[warrpath4x4]

I dont have any experience with a Holley sniper but, could your distributor be loose? I would think backfiring would be timing.

 

[Vbb199]

Theres a high chance your o2 sensor could be bad (they go out eventually) or you had an exhaust leak that eventually killed it
Whats the AFR when cranking ?

 

[Vbb199]

Or your fuel filters clogged, or an injector could be unplugged (all common)

 

[Ricko1966]

I'm thinking it's an ignition problem.

 

[Vbb199]

The gas soaked plugs is why i was wondering about an o2 sensor or a leak around it , much more than that, yeah probably the distributor moved or is acting up.

 

[Ricko1966]

Take an old spark plug open the gap wayyyy!!! up. Clamp the plug body in a jumper cable, other end of cable to ground. Put the plug where you can see it hook up a plug wire and crank. Tell us what you get for spark,is it consistent,blue and strong? .035 isn't going to cut it,it's firing in open air,with no compression and no fuel so use a big gap.

 

[edgephoto]

I have been lurking here for a while. Been in the automotive service business since 1985 and now am a Field Service Engineer for an auto manufacturer.

Backfiring out the intake is timing. Bring the engine to TDC, make sure the rotor is point to #1 on the distributer cap. Then check firing order. If that is correct, disable the fuel, connect a battery booster and perform a compression test.

The outer ring on the harmonic balancer could have slipped, make sure that you don't rely on that to get TDC.

 

[75BEASTK20]

Had a similar problem many years ago. edgephoto is correct on both his answers.

 

[CT210]

Its wintertime, have you driven through any water or washed down the engine? If so, look inside of the distributer cap for moisture. It will cause cross firing and symptoms like you're having. Start with the simple then work to the complicated.

 

[edgephoto]

What I tell technicians daily and when I was teaching, make a list of all the possibilities. Write it down.

Then all the things that can be checked and verified in 2 mins or less. Do those and cross them off your list (assuming you did not find the problem).

Then prioritize the list in easiest to hardest.

Anything that seems like a long shot or you think of as you go put on a second list. Stay focused and work the problem. Do not jump around!. Stay true to your list. You will find the problem if you follow logic and a systematic approach.