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Ready to shoot my carb!!!! Need help from carb guru's!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by barbastard, Sep 23, 2002.

  1. barbastard

    barbastard 1/2 ton status

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    Ready to shoot my carb!!!! Need help from carb guru\'s!!

    Ok guys, here goes my LONG story of frustrating carb problems.

    First the background info...I've got a 77 K5 with about a 12-14 y.o. 350 crate motor, mild "RV" cam, K & N filter, and other misc mild engine mods. May of this year I replaced the original quadrajet 4MV carb with a rebuilt quadrajet 4MV from a repuatable local carb rebuild shop. About the same time I also replaced the mechanical fuel pump with a new unit from Kragen, and added an inline fuel filter right before the carb.

    The new set up runs great on the road, actually better than it used to, and runs pretty much the same as it used to on flat trails. The problem is when I start to go up any serious incline on the trails...mostly rocks, and steep enbankements. The carb just seems to sputter out and eventually kill the engine. I am unable to start the engine until we take off the air cleaner assembly and either manually engage the choke on the carb and crank the engine over or cover the intakes on the carb with your hand while cranking the engine over. Unless one of those methods are used, nothing else works. I've tried holding the accelerator to the floor and cranking it over, holding the accelerator to the floor in between trying the ignition, pumping the accelerator, etc......nothing!!!!! /forums/images/icons/mad.gif

    Faced with this VERY FRUSTRATING problem I took my rig into a local "offroad" shop and told him my problems and asked him to check the seats and needle levels in the carbs, timing, and adjustment of the carb to see if any where the culprits of my dillema. His findings where that the needles and seats where adjusted fine, tweaked the air/fuel mixture a little bit, adjusted the idle some, and adjusted the idle on my choke and said that everything else was fine. His recommendations were to install an auxillary electric fuel pump to assist the mechanical one and also install a high flow in line fuel filter in lieu of the stock one currently installed. He felt that the mechanical pump was to weak to pump fuel from the tank to the carb at steap angles and that with assistance from the electric pump my problem would be cured.

    However, before I go and follow his recommendations I wanted to enlist the help of you guys. Any recommendations? Advice? Personal experiences?

    If it helps any most of the time this occurs I am at a higher elevation (6000 ft +), however it has happened to me at Hollister Hills (under 1000 ft). As far as I can tell the carb is being STARVED of fuel and therefore killing the engine. That's why the choke must be engaged or intakes blocked......correct??? Or am I way wrong??

    Any and all help would be interested!!!! Thanks for listening to my long ass sob story!!!! /forums/images/icons/crazy.gif

    Barbastard
     
  2. R72K5

    R72K5 Banned

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    Re: Ready to shoot my carb!!!! Need help from carb guru\'s!!

    if it was my ctruck, then i think that I would check for a kinked line or hose soemwhere from tank to carb and then if found nothing looking bad along there then i would probably pull the air horn off carb and replace main needle and seat, and then check float level and adjust if necessary, if anything i probably needs increased- from the sounds of it.

    do you eve rhave cut out or dead spot when first depressing accelerator in or out of gear(accelerating in or out of gear) ?
    the bogging down part: what gear ratio and trans you running ?

    good luck
     
  3. barbastard

    barbastard 1/2 ton status

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    Re: Ready to shoot my carb!!!! Need help from carb guru\'s!!

    TTT
     
  4. Thunder

    Thunder 3/4 ton status

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    Re: Ready to shoot my carb!!!! Need help from carb guru\'s!!

    Here's all I can think of.
    Fuel pump: maby its weak check the pressure. Should be around 4- 6 psi. The mechanical pump, if working properly should not need any help from a electric one.

    Check the fuel lines all the way back to the tank. Maby there is a pinhole leak that allows you to suck air when at steep angles. I had this problem in one of my cars. It would run out of gas on long steep grades. I went thru 2 fuel pumps before I found a tiny pinhole leak in the line back by the gas tank. It had rusted thru.

    Is the gas tank properly vented? Maby the vent hole in the gas cap is not working and you are building up a slight vacume in the tank and the pump is having a hard time pulling against it on a hard grade.
    Just a few ideas hope it helps.
     
  5. tipoil

    tipoil 1/2 ton status

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    Re: Ready to shoot my carb!!!! Need help from carb guru\'s!!

    just put a fuel presure gage on the line that goes from the fuel pump to the carb an go take a ride on a hill that will cause that bug that u mention and check the gage to see if it's not pressure related.
    if the pressure is to low buy a new pump or do a vacuum check on the line that goes from the tank to the fuel pump to see if there is not a restriction there (kink hose,pluged tank strainer,etc)
    u will need a vacuum/fuel pressure gage (they make a few gage that do both (vac+pres) not to pricy) and a brass tee so u can (tap)the line.
    if ur still not sure how to do it just pm me
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: Ready to shoot my carb!!!! Need help from carb guru\'s!!

    First thing is cripple the 4bbl lock out. It a little lever on the passengerside that the choke engages and jams the bottom plate of the 4bbl from opening. problem is it will engage when the truck tilts back. A Zip tie around a leg of the choke will do the trick. Now what this will let you do is get the 4bb's open and pull fuel from the secondaires and may keep it running.
    The rest is float level and possibly a missing slosh baffle in the carb. The primary jets are in the front of the float bowl. As the fuel runs to the back they start sucking air. the lower the float is adjusted the worse it is going to be.
     

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