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  1. #1

    Default 1992 4.3 sierra wont start unless gas petal to the floor

    what could be my issue? it only starts when i have the gas petal all the way to the floor.
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  2. #2
    stephan's Avatar
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    Sep 2010
    Far West, Oregon USA,
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    Take the air cleaner off so you can see the injectors in the TBI. Have a helper crank the engine while you watch the injectors with a flashlight. Are they spraying fuel as soon as it starts cranking?
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  3. #3


    Dirty fuel filter??

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  4. #4


    i will have my wife turn the key as i watch when i get home... the fuel filter thats on now looks fresh out the box. but i did use star bright star tron the whole trip home so maybe it cleaned the fuel tank pretty good and clogged the fuel pump. on a side note... symptoms before it started jnot startingk where taking longer to start. hope its not the fuel pump, buy it maybe what you guys think?

  5. #5
    stephan's Avatar
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    Far West, Oregon USA,
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    Since you made no mention of running problems after it starts, I'm assuming it runs fine after it starts, so I would give the fuel pump & filter a free pass for now. (It's much easier to look at the injectors at this point than to get a FP tester & check the fuel pressure (although this may be in your future) If the injectors aren't spraying fuel when first cranking, then the ECU is not grounding the injectors for the start. This is usually due to the ecm in the dist. not sending a strong enough pulse during cranking (slow speed) While you have the hood up, look at the wires coming from the distributor. Do you have the 4 wire plug?

  6. #6


    Almost definitely the coolant temp sensor. When they fail they tell the PCM the ambient temp is about 300 below zero. This causes the PCM to run a very rich mixture, usually to the point the engine won't start/run. When you put the pedal to the floor, it goes into flooded mode, and cuts fuel spray to almost zero. You need the sensor on the intake near the thermostat.
    When you hear hoofbeats, look for horses not zebras.

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