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Q-jet Carb ?

Discussion in 'The Garage' started by Chevit, May 31, 2004.

  1. Chevit

    Chevit 1/2 ton status

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    I have an 84 K5 and was woundering if a Q-Jet off and 85 with the electrical plug-in would still work on my 84?

    Thanks,
    Poor and Blue /forums/images/graemlins/blush.gif
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    If it is in fact a CCC than nope. /forums/images/graemlins/frown.gif
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Is there a connector at the top PS of the carb, and one at the DS front of the carb?

    If yes to both, it will only work on another vehicle with those plugs hooked up to the computer. If only the PS plug, then you can PROBABLY use it on your truck. Those were not computer controlled carbs.
     
  4. Dunc03

    Dunc03 1/2 ton status

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    IF it is a dual capacity pump then the carb can be used. If there were only two electrical wires connected to the top left of the carb (when facing the engine from the front of the vehicle) then it can be used. One wire will lead to the top of the water neck were the radiator hose connects to the engine. This acts as a ground when the engine reaches a certain tempature. When it ground it cuts the fuel flow in half. This devise was used to eliminate cold start problems. If you want to use this type of carb, but don't have the required electrical ground switch that is on top of the water neck, then you can just ground that wire to the block. I put a toggle swirch in the cab so I could still use it on cold mornings. Hope this helps.
     
  5. Chevit

    Chevit 1/2 ton status

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  6. dyeager535

    dyeager535 1 ton status Premium Member

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    You need to tell us if it is a CCC rig or not.

    I'm sure if you have a service manual it will tell you how to diagnose this stuff, but generally, if it is CCC, it will be very similar to TBI.

    There is no mechanical or vacuum advance on these systems, but there are things like TPS, MAP, O2, etc., that can be tested for proper operation.
     
  7. Chevit

    Chevit 1/2 ton status

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    [ QUOTE ]
    You need to tell us if it is a CCC rig or not.

    I'm sure if you have a service manual it will tell you how to diagnose this stuff, but generally, if it is CCC, it will be very similar to TBI.

    [/ QUOTE ]

    Nope just an electric choke
     
  8. Chevit

    Chevit 1/2 ton status

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    well...
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, I don't have much more to suggest actually. An intermittent problem like that is probably going to be something sticky, like the EGR valve (which you replaced) or advance weights. (also SHOULD be fixed apparently)

    If the throttle plate bushings are shot, the idle RPM should not be consistent...few hundred RPM difference every time.

    Since it is intermittent, it's not that something isn't adjusted right. Have you tried disconnecting the vacuum lines (and plugging them of course) for the EGR and vacuum advance, and testing it?

    I'd ignore the stock timing specs, and advance it until it pings under load, then back off a few degrees, making sure it still turns over easily. Not ideal method for timing, however, it still sounds like spark is occurring at the wrong time.
     
  10. Chevit

    Chevit 1/2 ton status

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    Could it be the fuel pump going out? I know they will leak but if the diapham had a small hole in it would this maybe cause this? Yesterday I replace all the rubber hoses running to the fuel pump and the ones 3/4 of the way down on the frame /forums/images/graemlins/1zhelp.gif
     
  11. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    Could it be the fuel pump going out? I know they will leak but if the diapham had a small hole in it would this maybe cause this? Yesterday I replace all the rubber hoses running to the fuel pump and the ones 3/4 of the way down on the frame /forums/images/graemlins/1zhelp.gif

    [/ QUOTE ] If it's a mechanical pump (On side of engine) it a $20.00 part and under a hour to swap out. I'd say hell with it and replace the pump. But if you have a electric pump in the tank, thats more expencive and too much work involved for a just incase.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Only fuel pump I've ever had fail didn't last a day after it first started showing symptoms. Stalled at a light, coasted down the hill, restarted, got to work 5 minutes later. Went to leave 4 hours later, got about 1/4 mile and truck died, that was it.

    Perhaps the mech. pumps can fail differently, but it seems unlikely to me.
     
  13. Chevit

    Chevit 1/2 ton status

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    /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gifIT WAS THE FUEL PUMP /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
     
  14. Muddytazz

    Muddytazz 1 ton status

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    Cool, glad to hear you got it fixed. Don't it always figure that its something simple /forums/images/graemlins/doah.gif
     
  15. Chevit

    Chevit 1/2 ton status

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    [ QUOTE ]
    /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gifIT WAS THE FUEL PUMP /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif

    [/ QUOTE ]

    /forums/images/graemlins/angryfire.gif Wrong again /forums/images/graemlins/angryfire.gif
     
  16. Chevit

    Chevit 1/2 ton status

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    /forums/images/graemlins/confused.gif maybe a clogged Catalytic Converter /forums/images/graemlins/1zhelp.gif
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Plugged catalytic converter SHOULD result in a decrease in performance as the RPM's climb. A plugged converter will NOT result in an intermittent problem.

    If you think the converter is plugged, if you have AIR, you can use a pressure tester to see what your backpressure is. IIRC, anything higher than 4PSI means the exhaust system is screwed up.
     
  18. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    Perhaps the mech. pumps can fail differently, but it seems unlikely to me.

    [/ QUOTE ]

    Nope. Last time mine failed I was pulling a trailer. I was going up a hill to drop the trailer off and it bogged and I wasn't sure why. Dropped the trailer off, drove a mile, shut it off, went in the store, restarted it and was on my way out of the parking lot when it died and it was done right there. Probably 5 miles from the first time I noticed symptoms.
     
  19. Chevit

    Chevit 1/2 ton status

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    I had the cat check out and it was OK just for the hell of it I started the POS for a minute then cracked the fuel line to carb. No fuel pressure, so I guess my problem is from the pump back /forums/images/graemlins/angryfire.gif here I go again...
     
  20. Muddytazz

    Muddytazz 1 ton status

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    Is it possible you replace the fuel pump with a bad one? I've bought new ones only to find out they were bad also. Do you have a known good one that you can swap in just to do a test?
     

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