Question about 1985 Chevrolet C1500

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I have a popping sound coming up from my carberator when i accelerate what can it be

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  • Mark Paxton
    Mark Paxton Dec 30, 2008

    no vaccum leaks checked all of those and changed the distributor to a late model timing is in as well 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    i have done the wd-40 test once before i think i may be drawing air up from my gas tank because i have low fuel pressure and it has a new fuel pump on it and my timing is at 4 btdc

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    im at my wits end i have rebuit engines before but i need help with this one 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    1985 chevy half ton 2 wheel 305 vin code h for high output

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    how would i be able to tell i have pulled the number one plug out and checked it the old fashioned way the distributor points to number one on the cap as well how can it be 180 out 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    thank you i have run the firing order numerous times and its all in the timing cap bug all of it i went over it with a fine comb 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    a lot of the smog stuff was removed prior to me buying the truck as it is  im running 150 psi on all cylinder the only thing i can think of is im missing something i even bought a late model no comp distributor with no computer controls in it 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    also i have the factory quad i have changed it out to a edelbrock 600 cfm it still does the same with it even

  • Mark Paxton
    Mark Paxton Dec 30, 2008

      do you mean that a valve may be stuck shut? if so i havent noticed any sort of loud noises coming from the engine it all seem to be oiling real good and i have checked all of the valves 

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    unhooked advance and checked it that way, still popped ,  the engine pick up when it is hooked upto constant vaccum  .

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    so i take it doesnt need constant vaccum ? just only when accelerating ?

  • Mark Paxton
    Mark Paxton Dec 30, 2008

    not to be rude boy do i feel stupid so what would need constant vaccum i mean the trucks really just stock it that doesnt work then what do you reccommend  i will be at a loss if i cant find this out 

  • tmartin001 Jan 22, 2009

    84 chevy el camino, 305 ci with 4barrel. Neutral or park can rev 4-5000 rpm without problem. Drop it in gear, AT, and it pops through the carb. I've changed filters, plugs, wires, HEI cap and rotor. Also tried another quad jet I own and the same popping. I've wondered about a valve spring, yet it runs smoothly in park or neutral.

    Scratching my head for answers!!!

  • fredfrog69 Feb 09, 2009

    i have a tapping sound coming from the top side of my 305 chevy , it has 122848 miles , it just started doing it yesterday , i m going to have to take valve covers off to see which push rod is loose or broke. What do think ?

  • L 2DA L Apr 09, 2009

    i have a 1978 chevy monte carlo, that pops and sputters or back fires only when i put it into gear. i can idle good an even rev up da rpm witout a single noise until i drop it into drive or reverse can some one please help me wit my pesky lil problem.

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  • 140 Answers

It's backfiring. This can be caused by a vacuum leak. If a vacuum hose falls off or wears out and leaks it will cause a lean condition that will cause the engine to backfire. If your not familiar with cars this should be a cheap fix.

Posted on Dec 30, 2008

  • 9 more comments 
  • David Robinson Dec 30, 2008

    The timing may be too retarded then. If not check for vacuum leaks around the base of the carb then the manifold.

  • David Robinson Dec 30, 2008

    What make and model? Engine size, tranny type?

  • David Robinson Dec 30, 2008

    Now don't get mad but, are you sure the distributor isn't 180 degrees out.

  • David Robinson Dec 30, 2008

    To refresh your memory when looking at the engine from the front the distributor rotates clockwise. The firing order is 1-8-4-3-6-5-7-2. Number one is on the drivers side front cylinder. Odds on the right even on the left.

  • David Robinson Dec 30, 2008

    Did you check number one by feeling the compression? Then check the timing mark to see if it agrees.What kind of carb do you have? Also do you have the charcoal canister connected?

  • David Robinson Dec 30, 2008

    Ok, back to the basics. Check your rockerarms. Make sure all of the valves are opening. If an exaust valve doesn't open then the combusted air comes back through the intake valve.

  • David Robinson Dec 30, 2008

    If it idles ok and only pops when accelerating then you need to check the vacuum advance. The port on the carb is the one that only draws vacuum on acceleration., not the one the has vacuum when idling.

  • David Robinson Dec 30, 2008

    Check the vacuum advance by taking off the distributor cap and sucking on the hose and see if the base plate moves. then hold the vacuum with your tongue and see if it leaks. If you hook the vacuum advance up to constant vacuum then it will move the base plate that the points/module sits on then when you accelerate it will actually ****** your timing.

  • David Robinson Dec 30, 2008

    ****** = deadvance

  • David Robinson Dec 30, 2008

    yes.

  • David Robinson Dec 30, 2008

    Air conditioning/heating ducts use vacuum, transmission modulators use vacuum, and some cruise controls use vacuum. Your new carb should have a couple of vacuum ports one for controls and one for the distributor.

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SOURCE: engine pops through carberator when accelerating

Its either the timing of the distributor OR the accelerator pump in the carby as it must squart petrol in a fraction before the engine accelerates
if not then like yours it sucks in air and the engine pops back in the carby ( and its been known to catch fire) so do it now as with out enging going air cleaner off and look in the top and see if it squarts fuel in straight away and no delays.
Let me know how you get on Ron

Posted on Nov 08, 2009

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Its either the timing of the distributor OR the accelerator pump in the carby as it must squart petrol in a fraction before the engine accelerates
if not then like yours it sucks in air and the engine pops back in the carby ( and its been known to catch fire) so do it now as with out enging going air cleaner off and look in the top and see if it squarts fuel in straight away and no delays.
Let me know how you get on Ron

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