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99 yukon no start please help

Discussion in 'GM Powertrain' started by joelk, Nov 22, 2013.

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  1. joelk

    joelk New Member

    I have 99 Yukon vortec 5.7 with no start issues. I have good spark to plugs and 55-60 psi fuel press. At intake port I can spray start fluid in throttle body and it will bust off til it burns it off ????? I tested crank sensor getting 5-6 volts DC to yellow wire as I turn motor by hand. Help on stranded thanks so much
  2. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    Does the fuel pressure stay at 60 psi while cranking? If you start with starting fluid, does the pressure stay high after it starts?
    Because it starts on starting fluid, that strongly suggests a fuel delivery issue. I would probably do a more thorough test of the fuel system.
  3. joelk

    joelk New Member

    Thanks for replying fuel pressure drops down to 40 psi while cranking.

    - - - Updated - - -

    It drops down to 40 whole cranking
  4. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    From what little I have seen diagnosing my own fuel system issues, these engines need 50+ psi of pressure to start/run well. Below 50 and they start to have problems. I expect once you resolve the reason the system is losing pressure, you will find the cause of your no start.

    Basically two causes for this:
    1) A bad fuel pressure regulator
    2) Something with the pump.

    Is the pump running while cranking?

    If the pump is running, what pressure is it capable of? This can be tested by carefully clamping off the return line (where it is rubber) and see what pressure is generated. If the system pressure jumps up (should probably go well above 66), that suggests that the fuel pressure regulator is opening too soon. If the pressures do not change, that suggests the pump is not able to generate enough pressure. Check for clogged filter or other kink/restriction in the supply line between the pump and the fuel spider. If the lines check out ok, then the pump itself is probably going bad.
  5. cmcolfax

    cmcolfax Member

    following... similar problems with my 99 Burb, 5.7...
  6. jdavis25

    jdavis25 Member

    I have the same problem with my 99 GMC Yukon identical I have same pressure same drop in pressure and I would spray starting fluid and it would stay started til it sat for hours well mine ended up being able to start by squeezing the return line down on the frame for the regulator and it had new fuel pump filter spark plugs and newer cap rotor I changed out the crank sensor if you have a known good crank sensor I'd change it to fully eliminate it was told those ohm test just fine but have been bad just some ideas interested in what you find

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