Hey all, I have a 2013 lt 4x4 crew cab with the 5.3 Over the last week or so when the truck has sat approximately 6-8 hours and you try to start it up, it has a hard time starting. Just turns and turns and then when it finally starts it idles rough for about 10 seconds or so and then lines out. Ones it lines out the truck runs like normal. You can even kill it and it will fire up like normal. I have changed the fuel pump, and the fuel purge solenoid. I have unplugged the maf sensor in hopes that that would work but did not. We plugged the truck into the hp tuners program to try and get an idea of what was going on and the only abonormalities we seen was when it was having the hard start that the injectors opened up to 113 before falling straight to zero and then opening again like normal and starting. Other than that we seen nothing else wrong. we killed the truck and ran the program with it starting normal and nothing reads wrong(that we can see). The biggest problem is that sense it is only doing it after it has sat for most of the day, its hard to test and try on what is wrong with it. Any ideas would be greatly appreciated! oh and its not throwing any codes what so ever.

 

Oh, the truck also has 129000 miles on it now. Yes I drive a lot.

 

put a fuel pressure gauge on the fuel rail and check for fuel pressure leakdown.
-install gauge
-prime fuel system, cycle key multiple times to run pump
-note psi
-note psi after 5 min...if no drop, continue to monitor...see what it is in an hour...next day

 

That's what I'm thinking