08 Yukon Starting Issue When Hot

[Lever23]

I have a 2008 Yukon (5.3L V8, Flexfuel) that's having some starting issues after running for an extended period of time. Engine turns over fine when cold, but after driving for an extended period of time (minimum 30mins, varying speeds - city, highway), shutting the engine down and restarting after 10-30mins the vehicle starts funny.

 

Instead of cranking over normally, it fires up almost immediately after turning the key - maybe half a crank. Engine then revs high for 5-10 seconds before returning to normal RPM. I've had the fuel pressure system tested and it came in at 55psi. I've also started monitoring if the issue pops up as the fuel level in tank decreases.

 

I'm wondering if the Fuel Pressure Regulator on the engine block or on the tank could still be causing an issue like this? Or if the Fuel Injection System might have an issue? Any other suggestions would be greatly appreciated. Thanks!

[Cnmx27]

My 2010 silverado 5.3 had the same issue. I had the dealer re-flash my pcm. There is a software update for your fuel/ethanol sensor. Mine thought gas was ethanol and started messing with the timing and fuel pressure. Hope this help, good luck.

 

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[Lever23]

Thanks Cnmx27, did they have any idea what caused the change in fuel type? My Yukon hasn't thrown any code errors, and I haven't had time to get it back into the shop since your reply. Will let you know what they say.