1. Welcome To GMTruckClub.com!

    The #1 Chevy Truck Forum Online
    Online since 2004, we are the #1 Chevy Truck & SUV forum and user community. If you have any questions about your Chevy or GMC Truck, SUV or Crossover, or just want to connect with other GM owners and enthusiasts around the world, you've found the best place on the internet to do that.

    Join Today ~ It's Free
    Registering is Free and Easy! Hope to see you on the forums soon!

1999 GMC Yukon 5.7 liter crank no start

Discussion in 'General Chevy & GM Tech Questions' started by jdavis25, Mar 25, 2014.

  1. jdavis25

    jdavis25 Member

    Hi I have a 1999 GMC Yukon with the 5.7 liter that I'm having troubles with. I have recently replaced my fuel pump, fuel filter, spark plugs, it has new ignition switch and it had newer cap rotor and plug wires on it. Hooked fuel gauge to it had 50 psi for the prime then dropped to 20 psi while cranking. To get it started I have to jump start it or ether which I nknow is bad for vortex engines but trying to get answers to point me where my problem is. Any ideas is greatly appreciated

    - - - Updated - - -

    Also as soon as I do get it started it starts up just fine aftwrwards , but qwhen it sits for a few hours it won't start again.
  2. Pikey

    Pikey Moderator Staff Member 2 Years ROTM Winner 1000 Posts

    how did the electrical connection look at the fuel pump when you replaced it? what brand pump did you install? just to clarify, it starts when you jump it? Have you looked at the fuel pressure regulator?

    - - - Updated - - -

    moved to General tech sub forum
  3. jdavis25

    jdavis25 Member

    It will start when jump started and ac delco fuel pump from car quest and I updated the connector when replaced the fuel pump. It started out to be just a hard start have to cycle keys for it to start and then this but that's what I've been reading was fuel reg but also I'm kinda thinking it may be a low voltage thing as well I do have a remote start on it and I just pulled the fuses for that I seen my security light flashing and gonna be buying a scanner to see if any codes are present later today

    - - - Updated - - -

    Well pulled codes only had a p0162 oxygen sensor and c0226 for abs gonna drop fuel pump and warranty it.

    - - - Updated - - -

    Sorry I was mistaking it was Delphi fuel pump
  4. Pikey

    Pikey Moderator Staff Member 2 Years ROTM Winner 1000 Posts

    delphi is a quality pump. Did you solder the new connector in or use crimp connectors? Also, how does the ground going from the pump look?
  5. jdavis25

    jdavis25 Member

    I crimped and shrink wrapped and I'll clean ground and the elimination
    Of the remote start was no good sat over night and no start

    Wish it could have been a simpler component like a trans the engine side to me is like Greek
  6. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    I don't understand?????? It will start if you jump start it with a 2nd vehicle.

    That means you do not have sufficient battery to crank and fire the plugs and pump the fuel.
  7. jdavis25

    jdavis25 Member

    That's what I first thought too but I have brand new battery out of my truck into my Yukon same problem its got me confused as well and when I done a voltage test it tested 11.89 the whole voltage system I was thinking maybe a pick up coil or crank sensor might do it as well but it sucksa that I don't have data stream on my scanner and like I said I don't understand why while cranking my fuel pressure drops to 20 psi I thought it should stay constant 60-66 psi
  8. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    My guess is that, if we can figure out why your fuel pressure is dropping off like this, we will figure out why it won't start. Does the fuel pump run while cranking? If not, will it start if you temporarily hard wire the pump so it will run? If you monitor the voltage to the fuel pump, is it getting the "signal" to run when it should? If the pump is running while cranking, is the something wrong with the regulator or the injectors causing the pressure to be too low? Those are some ideas of things I would check.
  9. jdavis25

    jdavis25 Member

    Think the relay might be able to cause problem like that and also as soon as I get it started for the day it starts no questions but if it sits for like longer than 5 hours or so it acts up again this whole situation is something and has me and a lot of good mechanics that i know baffled

    - - - Updated - - -

    Swapped fuel pump relay with my other Chevy with no problems and swapped battery just for reassurance and still same problem
  10. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    OK, how's this for a theory (guess). The relay contacts are welded together (electrical contacts will burn and weld together), so that the fuel pump runs all of the time. Let the truck sit for 5 hours and the battery runs down enough that it needs a boost. After starting, the alt recharges the battery, so that there is sufficient power to start the truck if it is shut off for a short time.

    A new relay fixes the problem.

Share This Page