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hesitates/stumbles w/full tank gas 850 1993

posted by  someone claiming to be Bob A.1 on  Sat Feb 26 05:28 CST 2005 [RELATED]

Just wondering if anyone else has seen this. After I fuel up with a full tank of gas, the car will hesitate and stumble from a stop light for about 5-6 seconds and then the car will accellerate normally from then on. It's wierd because it won't do it when the tank is less than almost full!
I should add that the car also has an occassional starting problem. On the first crank, whether cold or hot, it will not start. When I turn the key off and turn it on again to start, it will always start. The car never stalls or refuses to start on second try. I just wish the days of it firing up a split second after I hit the ignition were still here!
What should I start replacing, fuel pump relay, fuel pump itself, regulator?
I replaced plugs, wires, cap, air and fuel filters fairly recently.
Thanks guys!!








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    hesitates/stumbles w/full tank gas 850 1993

    posted by  ccox on  Mon Feb 28 07:48 CST 2005
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    I have the exact same problem with my 93 850. It has been happening to me for around 2 years now. I only see the problem when it is hot outside with a full take of gas. The winter time I do not have a problem. I have replaced both fuel pump relays, gas cap, fuel filter and none of that has worked for me. I don't want to spend the money for anything else so I just don't fill the tank all the way up. Not a great solution but the cheapest one. If anyone knows of a good cheap solution I would be glad to hear about it as well.

    Thanks,








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    hesitates/stumbles w/full tank gas 850 1993

    posted by  someone claiming to be Miker on  Sun Feb 27 06:13 CST 2005 [RELATED]

    Bob

    How full do you fill the tank up. Do you keep adding til it spills out the opening or let the pump shut off on it's own?

    Does the stumbling stop within a quarter tank or sooner after filling up the tank?

    If you fill it up too high in the tank I believe you can plug the breather hose and cause a temporary vacuum in the tank. Drive a few miles and lower the level of fuel in the tank and the plugged breather hose opens. No more stumbling?

    My guess anyway.

    Miker







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    hesitates/stumbles w/full tank gas 850 1993

    posted by  HD on  Sat Feb 26 08:47 CST 2005
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    last visit: Sun Jan 15 12:09 CST 2012
    [RELATED]

    By the sound of your problem it sounds to me that it happens only when you get gas. Could it be the gas cap?? In Texas when we go through state inspection they test the cap under pressure. Your problem could have something to do with the gas cap. Just a thought.

    Good Luck!

    Henry

    97-850/87, 98-S70/85k








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      hesitates/stumbles w/full tank gas 850 1993

      posted by  Erik A on  Sun Feb 27 07:44 CST 2005
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      last visit: Mon Aug 31 10:16 CST 2009
      [RELATED]

      The tank is ventilated through the charcoal canister in the engine compartment when the car is parked, the intention is to catch the fuel fumes. When you drive the car, solenoid valves will redirect the ventilation so the canister is vented into the manifold and outside air is allowed to enter the tank. If something goes wrong with the valves I guess there could be vacuum in the tank while driving, at least in theory...?
      If there is a air above the fuel, you would probably be able burn quite a lot of fuel before the pressure becomes so low that the engine stops since the air will give a "cushioning" effect. With no air it would be a much more definitive stop. Have you tried to open the tank cap when it has stopped, does it suck in air?







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