Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

q-jet issues

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by leadfoot067, Sep 21, 2005.

  1. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    im having a problem with the power piston in my q-jet....its sticking,sometimes it sticks open and sometimes it wont open at all...its a not very old jet stage 2 q-jet...the piston is clean so is the bore it rides in,ive changed springs to both stiffer and softer,ran some emery cloth in the bore and on the piston..even tried a different piston...still sticking....anybody have this happen? and solve this problem ive run out of ideas on this thing... :confused:
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    You mean the accelerator pump I suspect?

    It sounds to me like the accelerator pump shaft is binding on itself. If I'm not mistaken it's two pieces, one slides into the other as it's compressed, that's the only bind point I can think of, either that or the tip that sticks out of the carb is sticking on the hole in the casting itself for some reason. (angled load from the accelerator pump arm?)
     
  3. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    no its the piston that holds the primary metering rods...actuated by vacume(sp)
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    It can't be as simple as the air horn gasket being installed wrong can it?
     
  5. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    well i dont think so...that gasket only fits one way...ill look anyways..
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    Installed one way, but sometimes you'll see it installed with the gasket riding the power piston assembly. I'm sure you'd have seen it like that if it were, when you were in there before.

    You say it's sticking, is it possible to make it do this with the air horn off just pushing on it, or is it something you know is happening, and when you pull the air horn off you see it?
     
  7. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    it can happen either way...i also know it does it when its running..i can stick a paper clip down the hole..and watch it move up and down when its working..then ill go for a drive and it will backfire thru the carb cause its stuck(leans out when it doesnt open)..or when it stuck open it will black smoke at idle..in the past ive seen them stick from carbon buildup and stuff..but this carb is close to new...no carbon in there at all,and the passage for vacume that operated the piston is clear....im simply lost as to why it sticks...i took another piston and emery clothed it for a long time...its real small in the piston bore and it still sticks...
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    OK, so how about the little plastic piece that holds the top of the piston assembly in place? No binding on that?

    If you remove the needles, does it still stick? (definitely the power piston itself)
     
  9. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    havent tried it without the needles...i re-used the plastic thing from the original piston..hmmm...that could be it...
     
  10. JonV

    JonV Registered Member

    Joined:
    Mar 17, 2003
    Posts:
    27
    Likes Received:
    0
    Location:
    Hesperia, CA
    Jon V

    Alcohol content is high in some of todays fuel. (oxygenated fuel for cleaner emissions). The alcohol can cause the rubber seal on the piston to swell. When you take it apart, the alcohol evaporates, the rubber shrinks back, the piston moves without binding. You can tell by the rub marks on the cylinder. Change gas; maybe a new piston has newer better rubber.
     
  11. nstarry

    nstarry 1/2 ton status

    Joined:
    Feb 13, 2004
    Posts:
    349
    Likes Received:
    1
    Location:
    st.cloud minnesota
    I second that little plastic peice
     
  12. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    ok saturday i took the carb apart again..checked the plastic thing,gasket,and everything else...I GIVE UP NOW...selling the jet stage 2 q-jet....
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    Not like it's right next door, but you are welcome to come over to my place and we could play around with it and the multitude of rebuildable Q-jets/parts I've got laying around, see if we can find/fix the problem.
     
  14. leadfoot067

    leadfoot067 1/2 ton status

    Joined:
    May 14, 2001
    Posts:
    1,563
    Likes Received:
    0
    Location:
    puyallup, washington
    well i put my edelbrock q-jet back on the blazer and it of course runs great again...thanks though...im just gonna get rid of it now..
     

Share This Page