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Why must my truck die when I floor it?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by PetaKane, Apr 4, 2003.

  1. PetaKane

    PetaKane 1/2 ton status

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    If I slowly press on the pedal, it does just fine, but if I try mash on it from idle, it dies. Or if I just push it all the way in real fast then let go, it'll start to die and then idle back up. Does this sound like a bad fuel pump? It's died on me a couple times at stop lights and it's pretty embarrassing. Thanks
     
  2. tecton

    tecton 1/2 ton status

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    mine does the same thing if i step on it when i first start it...or if i let off the pedal fast or go over a hill itll choke or even flat out die
     
  3. Sandman

    Sandman 3/4 ton status Author

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    Sounds like its flooding out on you.
     
  4. sled_dog

    sled_dog 1 ton status

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    my friends 84 k20 does this too. he put a new fuel pump on and it helped but it still isn't perfect. SO I don't think its the flooding problem since its better with a better pumping fuel pump. My friend has an aftermarket Holley carb and I have a stock quadrajet I think maybe his secondaries are opening way too soon.
     
  5. bryguy00b

    bryguy00b 3/4 ton status

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    i have the same thing..i have a holley to..when its cold..and in park..if i rev it fast it will do that..but not after its warm..but when im driving and floor it i have to do it slowly...but usually if i slam the pedal it will stutter then go...im thinking about switching back to a quadrajet anyway...
     
  6. sled_dog

    sled_dog 1 ton status

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    see before the fuel pump if you slammed it my friend's 84 would just stall. Now with the new fuel pump it doesn't stall it just stutters really bad and goes.
     
  7. PetaKane

    PetaKane 1/2 ton status

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    Is there something I can adjust on or inside the carb to keep this from happening?
    /forums/images/graemlins/confused.gif
     
  8. bryguy00b

    bryguy00b 3/4 ton status

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    hmmm thats wierd..must be something with the carb i would think...the engine and trans and t-case has all been rebiult befor i got the truck..and they swapped in a 350 instead of the 305 when they did it...i dunno..i was thinking about running some STP in it for sh!ts and giggles..i havnt heard to many good things about holley anyway...
     
  9. Z3PR

    Z3PR Banned

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    I had that problem on my first K5. It turned out to be a clogged fuel line. It's kinda a PITA, but I'm a firm beliver in replacing the stock fuel line with a much larger braided steel line. Double the size will help with the fuel flow. Blow out the old line, and leave it on for a fuel return line if you ever wanta go FI. /forums/images/graemlins/thumb.gif
     
  10. Sandman

    Sandman 3/4 ton status Author

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    Maybe I'm bass ackward and its running out of fuel. /forums/images/graemlins/grin.gif
     
  11. bryguy00b

    bryguy00b 3/4 ton status

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    yea thats what i think might be up with mine..considering it sat for a while and all..thats why i wanan try some of that STP stuff befor i get into anything major. it runs good...just cant floor it real quick unless its really warmed up and all.
     
  12. wrathORC

    wrathORC 1/2 ton status

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    Everybody loves quadrabog.

    Yank your air cleaner. Climb up on the truck so you can see down the throttle body. Don't impale yourself on the air cleaner rod. Not that I've ever done that. /forums/images/graemlins/grin.gif Stupid milk crate sliding from under my feet...

    Grab on to the throttle and move it slowly to WOT. There should be two steady streams of gas about the diameter of a pencil lead--one shooting across each barrel. If she runs out of petrol before you get to WOT it's time for a new accelerator pump. If it's not shooting across it's time for a new accelerator pump. If there is a spot where it doesn't squirt much fuel it's time for a new accelerator pump. If it doesn't squirt much fuel at tip-in it's time for a new accelerator pump.

    You can adjust the accelerator pump by bending that little green arm. If it doesn't squirt much at tip-in you can bend it so it pushes the plunger down sooner. This will help a little. This also might be a hint that your float level is wrong. But I'm not here to fix that problem. Also, make sure that the rod that goes from the throttle to the accelerator pump is on the hole closest to the pump. This will give you more travel and therefore dump more gas down the intake.

    You also might have one of the more common causes of quadrabog. It's got to do with the timing when the secondary air valve flings open. You want it to open about 1 second after the secondary throttle valve opens. If it opens too late it'll fall flat on its face and then take off. If it opens too soon you'll have it flinging open, slamming shut, and flinging open again. This can be adjustd with the set screw for the spring on the throttle side and with the vacuum motor's orifice diameter. I choose to eliminate the vacuum motor because it's more crap to go wrong. I do all my adjusting with the spring. Some people think this is stupid. Adjusting the vacuum motor is a nightmare that involves either paying $12-15 for an adjustable motor or spending time drilling holes with itsy bitsy drill bits. Usually in the .030" range which is expensive. You either need to buy wire-gauge sized bits or buy some torch orifice tip bits.


    If you're not sure about the accelerator pump, go buy a new accelerator pump. I prefer the ones that push the rubber piston out to the walls but since these pumps are getting so hard to find take anything you can get. You'll have to pull the top of the carburetor off. I think there are six screws. Don't drop any down the intake.
     
  13. bryguy00b

    bryguy00b 3/4 ton status

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    would any of this have to do with my truck stalling out when i go to D. if its realy cold out and i let my truck warm up for a while..it will idle ok..but when i go to D it will stall out..or i have to pump the gas to get it going..and usually i cant get it to go so it takes a couple tryes..but once i get it past that little hump...it will be fine.
     
  14. wrathORC

    wrathORC 1/2 ton status

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    A carbureted engine isn't going to want to take off until it reaches half its operating temperature. It definitely isn't going to go anywhere until the choke opens.
     
  15. bryguy00b

    bryguy00b 3/4 ton status

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    yea thats all i think it probobly is..but my dads 79 with a 350 and q-jet doesnt take much to get it going..who knows..different carbs..(plus im pretty sure my choke is goofy to...i dont think it works right half the time..thats why im ganna switch to a manual one of these days)
     
  16. sled_dog

    sled_dog 1 ton status

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    when my truck is cold it won't move. You floor it and it pickups up a little then jsut misfires on like 7 of 8, has just enough to keep running. But if she is warm I can STOMP it and it won't sputter at all just GO. Well go slow man I need new gears. Thats a 355 with Quadrajet and 600 miles on it.
     
  17. DrMaserati

    DrMaserati Registered Member

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    It's starving for fuel when you push the pedal down fast. The best advice you've gotten is from wrathORC. It's probably mainly the accelerator pump. While you have the top off the carb I would also suggest you go ahead and replace the float.

    Here's an additional tip that he forgot to mention. When you remove the top of the carb, you should see two small tubes pressed into the bottom surface of the top. You will most likely find one or both lying in the bottom of the float bowl. They need to be put back and epoxied into place.
     
  18. MA87K5

    MA87K5 1/2 ton status

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    If you still have the tbi system then check your fuel filter. I also have an 87 k5 with the tbi. When that same problem happened to me I replaced the fuel pump with no change, then after I changed the fuel filter, it ran like a champ.
     
  19. bryguy00b

    bryguy00b 3/4 ton status

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    oh i didnt know you had FI....nm lol i got carb could be different there..
     
  20. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I have said it once and I will say it again (fire retardeant underwear on so flame away) Only poeple who don't want to learn or can't figure out the Quadrajet think it is a piece of junk follow the advice given here and your carb will idle over the roughest terrain give you better mileage than any Holley and have great power you just have to spend a little time with them. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     

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