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QJET GURU needed. HELP!!! More info.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Hossbaby50, Feb 13, 2003.

  1. Hossbaby50

    Hossbaby50 3/4 ton status

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    I need HELP!!!. I just got done changing the fuel pump in my truck a second time, because I thought that might have been my off idle acceleration problem. The second fuel pump didn't change my problem.

    Now I am thinking the accelerator pumps might be the problem.

    When I try and give it gas it stumbles bad or if I hit it real hard it will die. If I get into the gas very slow it will accelerate the motor perfectly. I can rev to 3500+RPM no problem if I get on the gas slow. But if I try and get into the accelerate at a normal rate then it stumbles BAD.

    Could this possibly be the accelerator pumps clogged or bad. If so how can I change them? PLEASE HELP!!!

    Other info: MSD cap & rotor. Less then 6 months old. along with full MSD igniton system. The motor is a 350 fairly stock.

    *** It is running rich I know because I relocated to Colorado from Arizona. If I pedal the throttle fast at low RPM the carb will load up and backfire threw the carb and also threw the pipes.*** Also it seems like the motor will run better with alot of initial timing. (16*+ BTDC)

    I need to get this thing on the road. Thank you

    Harley
     
  2. the professor

    the professor 1/2 ton status

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    Re: QJET GURU needed. HELP!!!

    Not enough info:
    -
    Sure its the carb...??
    Could be the rotor (burn through) / cap /coil...

    Did you change the inlet filter in the carb...(its behind the big nut/fitting the fuel line screws into) /forums/images/graemlins/cool.gif
     
  3. MilpitasK5

    MilpitasK5 1/2 ton status

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    Re: QJET GURU needed. HELP!!!

    maybe timing?
    Mine was doing that when I put the distributer cap on crooked too.
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    Re: QJET GURU needed. HELP!!!

    I haven't touched my dis. cap since I have replaced the fuel pump or since I have been in CO. (1 month) I set my timing several times. After I replaced my fuel pump the first time I had to advance the timing alot to get it to start, but after i fire it up I can run it off normal timing. (8-10* BTDC).

    Could this be a problem with the fact that my carb is running rich, and the new restored full fuel pressure? If so how can I adjust my carb down a little so it runs more normal? How do I lean out my mixture?
     
  5. MilpitasK5

    MilpitasK5 1/2 ton status

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    Re: QJET GURU needed. HELP!!!

    You need a special tool to adjust the carb. Have you ever had it rebuilt?
    I just had mine rebuilt. My symptoms were completely different then yours though.
    The guy that rebuilt it said that my float was just about shot and I had some rod that was bent inside the carb.
     
  6. Hossbaby50

    Hossbaby50 3/4 ton status

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    Re: QJET GURU needed. HELP!!!

    Yes, I have had it rebuilt before. Several time actually. I have never done it myself though. How much is this special tool to adjust the carb, where can i pick one up at, and how exactly do I adjust it to make it lean out a little? Thanks

    Harley
     
  7. MilpitasK5

    MilpitasK5 1/2 ton status

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    Re: QJET GURU needed. HELP!!!

    Sorry brotha'! I'm not guru. As far as I know, the carb adjustment tools aren't available over the counter. I think there are some on this board that have made one but I don't know who. Do a search and try to find 'em. It's alittle tool that you can turn a knob on top of the carb to adjust it. I think I may have saved some old posts. I'll take a look for you but definitely try a search.
     
  8. MilpitasK5

    MilpitasK5 1/2 ton status

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  9. MilpitasK5

    MilpitasK5 1/2 ton status

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    They guy that rebuilt my carb says they they all (quadracraps for our years) generally run rich.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    My truck was the same way, as I said in the other linked post, timing was it. I didn't waste time on the timing light, I changed timing until the hesitation/pop through the carb was gone when gassing it, and it happened to still start fine, and not ping, so I left it alone.

    Rich is going to need to be adjusted as well. You can test the accelerator pump with engine on or off. On, press it down with your finger, while its idling. Idle will change if its working. Off, after its been running, pull the air cleaner, look down the primary bores, and move the throttle linkage to WOT. You'll see gas squirt forcefully out into the venturi's if its working right.
     
  11. Hossbaby50

    Hossbaby50 3/4 ton status

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    I pulled a spark plug just for shits and giggles to see if the plugs were fouling from being overly rich. I pulled one of my plugs that is always worse then the others #6. (#8 is usually the worst but alot harder to get to).

    The plug was very black (rich). It is alot worse then when I pulled the plugs about 3 weeks ago. They were dirty then and a little rich, but now they are really bad. They are literally black from being so rich. I also get the black smoke out of the exhaust when I try and step on the gas (same time the motor stumbles).
     
  12. weisel

    weisel 1/2 ton status

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    Before I start pointing fingers twards my quadrajet, I check timing, and for vacume leaks. When I know those arent wrong, then I go to the carborator. Tuning a carb for an engine mistuned in another department is useless. I wish I could help with your carb though. I had problems with mine and bought Doug Roe's book on Rochester Carborators and found it very informative and helpfull. I can't remember most of it, but I think of it as the bible or quadrajet info. Get a copy and make it work for your problem. It's really complex but I think anyone could figure it out. But I would still check those first two things, timing and vac leaks.
     
  13. Hossbaby50

    Hossbaby50 3/4 ton status

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    I have checked the initial timing. It is on at about 8-9* BTDC. I have looked for vacuum leaks too, and I can't find any. I did notice that one line coming from the emissions canister is partially cut, but not all the way threw from what I can see. I didn't have this problem 1 week ago before I replaced my fuel pump. I am thinking since the carb is now getting full fuel pressure it is making it run richer then it was, and it was running rich with the previous pump. But I don't know for sure.
     
  14. Highlander

    Highlander 1/2 ton status

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    Harley the tool I use for adjusting the Idle mix. I got at Checker I think it was. But I'm pretty sure you can get it over the counter. But in later models of Q-jets they put a plug over the screws that you need to adjust.
    Now you said it has been rebuilt so maybe those plugs are gone.
    When I adjust the Idle mix I use a Vacuume Gauge. If you plan on keeping the Q-jet go get a Book on that carb. Doug Roes is great I've had it I now have a Haynes Techbook, I couldn't find the other one at the time.
    To bad you up in Fort Collins


    Eric
     
  15. DesertDueler

    DesertDueler 1/2 ton status

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    I would rebuild the carb, downsize the jets you have in it a couple of steps, and put a new set of plugs in it. If that doesnt take care of it, you will need to adjust the carb, but that is alot easier to do at a shop with a 5 gas analyser.

    Dan /forums/images/graemlins/burb.gif
     
  16. Hossbaby50

    Hossbaby50 3/4 ton status

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    Where exactly are these plugs, and how do you adjust them to lean out the mix? How hard is it to rebuild and rejet a Qjet carb? Basically I need to at least lean out the mix for it to run enough to be driveable. Right now I have to bum rides to the parts store or have FortCollinsRam bring parts to me. Thanks

    Harley
     
  17. Highlander

    Highlander 1/2 ton status

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    There are two of them in front about 3in apart I guess. they are on the very bottom part of the carb called the base plate a Q-jet has three main parts the Airhorn the Fuel bowl area ( I forgot the right name lol) and the base plate. the tool I have for the screws has a spring type thing with two differnet ends one has a slot the other has something like a Allen head. there is also a deal that slides back and forth that is so you turn the tool and the screw in or out. But in your case I'm sure you will turn it in. What I would do is turn it all the way in and back it out till I got the highest vauume. I would do that to both sides. I want to say you mite go 2 1/2 to 3 turns at lest where you are now days if you were back at sea level you could go more maybe to 4 turns I don't know for sure though.
    this site mite help you Q-jet tuning I hope this helps

    Eric
     
  18. BlazerWheels

    BlazerWheels 1/2 ton status

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    Harley, I have the EXACT same problem. My '85 stumbles and nearly dies if I try to gas it normal or hard, but if I ease into it it'll go fine. I only notice it though when it is cold, is that the case for you as well? I have to get smogged (CA and all) next week, then I am going to start searching for the problem. Keep us posted with what you find. Good luck
     
  19. BlueBlazer

    BlueBlazer 1/2 ton status

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    You need to adjust the tension on your secondary flapper dampening spring. Its opening too fast and making the engine run extremely lean.
     
  20. NE79

    NE79 1/2 ton status

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    Picked up the adjustment tool at harbor freight for $5, it got me through emissions.
     

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