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Need help troubleshooting Quadrajet...

Discussion in 'The Garage' started by poinzey, Nov 7, 2005.

  1. poinzey

    poinzey 1/2 ton status

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    Background: Back in July I took the blazer on a camping trip to Padre Island(roughly 1200mi round trip). It performed flawlessly until I got close to home. At the first light coming off the highway it died, started right up again pumping the pedal, but was idling horribly after that, had to keep pressure on the pedal to idle smoothly and seemed to be running extremely rich. Anyway, rebuilt it about 2 mos ago, and it was still doing the same thing afterwards. Yesterday I went out to tackle it again, and it looked like the top gasket is extremely wet with fuel, so I tightened all the screws on the top, readjusted everything and it was running pretty decent. Then...after going on a short trip(about 20mi), it started idling rough again. The problem seems to go away after sitting for a while and come back after it has been run for a long period(10-20mi on the highway). Any ideas what I should be looking for? Vacuum looks good, was getting about 15 off one of the front ports at idle.
     
  2. 77crewcab

    77crewcab 1/2 ton status

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    Mine did that when I first got it. The fuel filter was old and the PO had also run the fuel line where it was just a rubber line from the mech pump and draped across the engine. when the engine got to operating temps there would only be dribble of fuel getting past the clogged filter. The fuel line was getting so hot it was evaporating the fuel. New stock hardline and new filter fixed the problem.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    If you can reasonably predict when the issue will occur, I would try getting it to the point right when you think you will have the problem, pop the hood, and take the air cleaner lid off.

    If the gasket is wet on the outside, you may have fuel coming out the top of the carb (bad needle/seat, bad float or float height) which is leading to the wet gasket look, and some of that excess fuel is making it's way back into the carb, affecting idle quality.
     
  4. Cricket

    Cricket 3/4 ton status

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    Had a similar problem on a C10. If you know how - remove the top of carb and check for debris in the fuel bowl getting in the way of your needle & seat.
     
  5. poinzey

    poinzey 1/2 ton status

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    I think yall have got me on the right track, as I think I'm fighting multiple problems. There is about 18" of rubber fuel line going from the carburetor back to the hard line, which stops behind the alternator. I'm not sure if this was factory style or not, as the carb has the inlet pointing to the side. When I originally rebuilt the motor I had to replace the fitting for the fuel filter, as it was rounded off, but it was the same style. I think I need to swap to an inline filter and see how that does. Also reroute the fuel line a lil further away from the heater hose. It's just wierd that it was running for over a year like that with no problems. I wonder if thats why I had to adjust the float level so much when I redid it. Going by the spec sheet in the kit, it was a huge difference lower than before.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    If you can, get the stock steel fuel line on there IMO. The stock fuel filter will unseat if it clogs up, so if you replaced it and put it together right, it won't be a restriction even if it got all plugged up for some reason.
     
  7. poinzey

    poinzey 1/2 ton status

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    Do you know if that inlet repair fitting is the same as stock? If it isnt I should be able to order one to get the steel line all the way to the carburetor.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    The inlet repair fitting...

    Lets see...the repair piece I'm thinking of threads into the carb body, or maybe it replaces the entire piece that threads into the carb and holds the fuel filter?

    I don't believe the repair piece is made to thread the steel line into the part that holds the filter. Having never used one, but from how you talk, I'm assuming the repair piece simply replaces the whole filter housing, in which case it would make sense for that to be compatible with the stock steel line. But if the piece is aftermarket, all bets are off of course. :)

    I'm sure someone here has used the repair stuff can can comment.
     
  9. wildbilzrydn

    wildbilzrydn 1/2 ton status

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    You can get a brand new pump to carb fuel line here:

    http://www.inlinetube.com/

    If the fitting with the "big" hex on the carb is rounded, you can probably get one off another Q-jet. If not, I believe these lines come with the pipe fittings captive on the line, under the flare.
     
  10. Cricket

    Cricket 3/4 ton status

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    If you use the threaded repair fitting make sure you get it in right the first time. You'll be cutting new threads on the way in.

    I always had to use plumber's tape on mine, got tired of dinking with it and just got a good used carb body from the salvage yard.
     

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