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I have a 2008 gmc sierra 1500 4x4 .. Stopped a few weeks back for gas and it didn't want to start after fueling up. It would turn over and keep turning. So I shut the key off tried again, same thing. Finally it started. No problems with it starting until I stop for gas again..Same thing. so we replaced ignition and starter. Still the same issue. It has only not wanted to start twice while not right after a fuel up. Any ideas what it could be? Mechanic wants to change ignition switch and says after fueling up and it not wanting to start is just a coincidence. I'm beginning to disagree.
 

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If this problem is persistent and you can make it do it every time and it only does it at the this particular time then it isn't "just a coincidence". When you try to start it turn the key to the on position but right before starting it. If you hear a whizzing noise that means that your fuel pump is working. You can rule that out. Next I would check to see if there is any codes in the system. Even if your Check Engine Light (CEL) is not illuminated you may have some codes in the system (not all codes will turn on the light). If you have any kinda of issues with the evap that could be a contributing factor.

The next time this occurs, do not try to start it again right away. Turn the key to the Key On Engine Off (KOEO) position until you hear the whizzing noise go away and then turn it off and back on to the KOEO position until the whizzing noise is gone again. Do this about three to four times and then try to start it. If it starts every time like that, chances are that you have an issue with the fuel system. Whether it isn't getting the appropriate pressure or if there is a leak. If you have a pressure gauge you could hook that up and see what the pressure is reading and if it is low then the fuel pump could be the problem.
Keep me posted.
 

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Remove the line from the purge valve under the hood and start the truck. There should be no vacuum at the purge valve, if there is replace it. If there are charcoal particles in the line or valve you have other problems as well.

When you fill the tank fuel vapors are forced into the charcoal canister, to be purged later while driving. If the purge valve is leaking it can force these vapors into the engine and when you try and start it the mixture is too rich and you get a hard start.

One thing that may help in this case, key ON and wait for a few seconds, then hold the gas pedal to the floor (clear flood mode, turns off the injectors) and try starting it.
 

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GMT604 said:
Remove the line from the purge valve under the hood and start the truck. There should be no vacuum at the purge valve, if there is replace it. If there are charcoal particles in the line or valve you have other problems as well.

When you fill the tank fuel vapors are forced into the charcoal canister, to be purged later while driving. If the purge valve is leaking it can force these vapors into the engine and when you try and start it the mixture is too rich and you get a hard start.

One thing that may help in this case, key ON and wait for a few seconds, then hold the gas pedal to the floor (clear flood mode, turns off the injectors) and try starting it.
How do you remove the line from the purge valve? I'm having a bit of a hard start issue and am wondering what is causing it.
 
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