Backfire through carb under acceleration? UPDATE / another question

[ndemge]

Here's one for ya'll...<br /><br />My '84 F250, 460<br /><br />If you punch it, it backfires through the carb like it's coughing....<br /><br />what's the dealeo?

 

[kenimpzoom]

Re: Backfire through carb under acceleration? UPDATE / another question

Does it do this from a stop, or from rolling down the road?<br /><br />My 66 Impala did that, I solved it temporariliy by wiring the choke halfway closed. The thing was running lean and I didnt want to fool with it.<br /><br />Solved the problem.<br /><br />Ken

 

[ndemge]

Re: Backfire through carb under acceleration? UPDATE / another question

say I'm in 4th gear, doing 40mph, and punch it to pass, it will do it...<br /><br />If I very gently accelerate I can get it to WOT without this happening

 

[kenimpzoom]

Re: Backfire through carb under acceleration? UPDATE / another question

Might be an ignition problem, how old is the cap/rotor/wires?<br /><br />You can have a crossfire problem that only happens under hard stress.<br /><br />I had tiny cracks in the distributor cap once and it cause all kinds of problems under hard stress, but it would idle fine.<br /><br />Maybe time for a carb rebuild.<br /><br />Ken

 

[kenimpzoom]

Re: Backfire through carb under acceleration? UPDATE / another question

Maybe the accelerator pump on the carb is shot.<br /><br />Does it pop once, or does it backfire continuosly?<br /><br />Ken

 

[heycods]

Re: Backfire through carb under acceleration? UPDATE / another question

If it has a Holly carb on it it has blown the econimizer valve in the carb. Sometimes hapens when the timing chain is getting bad, or if It was a chevy, maby the cam going flat.

 

[JB]

Re: Backfire through carb under acceleration? UPDATE / another question

Collapsed lifter, bent pushrod or bad rocker arm on an exhaust valve will do that. Exhaust doesn't get out and pressure is still high in the cyl when the intake opens.<br /><br />If it is regular, like once per cycle that is where I would look first.<br /><br />If it seems more random look to the advice above.

 

[ndemge]

Re: Backfire through carb under acceleration? UPDATE / another question

JB, KEN.... Yeah, it does it more than once, I never let it go past 2-3 pops before my foot is off the gas.<br /><br />Would compression check tell me anything?

 

[Bondo]

Re: Backfire through carb under acceleration? UPDATE / another question

Would compression check tell me anything?

Ayuh,.........<br />It'll tell you the general over-all condition of the combustion chambers.......<br /><br />My 1st Guess for your issue is,...............<br /><br />It's going Lean,....... Check, or Change the Fuel Filters,+ have a look at the Carb......

 

[Limited-Time]

Re: Backfire through carb under acceleration? UPDATE / another question

Going lean with throttle plates are "punched" open. Lean pop, I'm with Bondo on the fuel starvation.

 

[ndemge]

Re: Backfire through carb under acceleration? UPDATE / another question

Ok bondo, I looked at the carb, its there.<br /><br /><br />now what?

 

[kenimpzoom]

Re: Backfire through carb under acceleration? UPDATE / another question

Look inside the carb and hit the throttle and see if the accelerator pumps fuel.<br /><br />Do this while the engine is off. <br /><br />Ken

 

[ndemge]

Re: Backfire through carb under acceleration? UPDATE / another question

One of the spark plug wires was off the spark plug.<br />engine also seems to be running a bit smoother now too Will see on the ride home if the problem goes away.<br /><br />I think the acccel pump is working, at idle, if I punch the gas it responds instantly.<br /><br />QUESTION:<br /><br />Where the heck do I hook the wire for a tach??<br />man I want a chevy....

 

[Reel Poor]

Re: Backfire through carb under acceleration? UPDATE / another question

Where the heck do I hook the wire for a tach??

To the negative side of the coil.

 

[steamboatwilly]

Re: Backfire through carb under acceleration? UPDATE / another question

NoelMG ,The time is too low.