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Q-Jet downhill ??

Discussion in 'The Garage' started by jms, Oct 13, 2006.

  1. jms

    jms 1/2 ton status Author

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    '85 Q-jet, electric choke, has the solenoid in addition to the mechanical accelerator pump, but not the full computer control (TPS, power piston solenoid etc.).

    The carb is running pretty good uphill and at side angles, and I can stand the truck on the (new!) rear bumper and it'll keep running smoothly.

    Not so on the downhill side. On really steep descents (the nose-in-the-ground kind), it'll want to stall - meaning no power steering, and no vacuum assist. Since the brakes are good, I've always just wrestled the truck down, and once flat, it starts right up. It's not flooding, exhaust is not black soot, it appears to be starving for fuel.

    So last week in Moab while descending WipeOut Hill, the same thing happens - the motor dies. But this time, I put it into park, and tried to start it. It coughed a bit, started, and to my surprise, I was able to keep it running with a little throttle (i.e. slight opening of the primaries). Trying to let it idle would stall the engine. So I keep it at 1000 rpm, put it in neutral, and proceeded down the hill, without any problem. As I said, the brakes work well (disk f/r), so nobody freak out over perceived safety issues - I rather inch the truck down an obstacle by using the brakes compared to having the auto in gear but the truck gathering too much momentum.

    So, am I missing something in the adjustment of the carb that would address this issue? I'm not quite sure where it draws fuel in idle, and whether these ports would be uncovered due to the angle (gas tank was near full, so pickup didn't seem to be an issue). This only happens at the really steep steeps, so for most of my 'wheeling, it's not an issue... but if I could make it go away at the next rebuild, I'd like to do so...thanks, michael
     
  2. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    its in the way the floats are hinged. happened on mine, now it happens on my truck avenger. Just don't go downhill.:D
     
  3. jms

    jms 1/2 ton status Author

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    I thought that was it, but now I'm not so sure. Since I could keep the engine running with light throttle, it means the float bowl wasn't empty. At that angle, the needle is not resting nice and tight in the seat - could it mean that a little more fuel pressure (due to the increased rpm) could fill the bowl enough to keep the engin running?


    As much as I like the mountains, it's not an option...:laugh:
     

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