tankmaster909@gmail.com

2008 Chevy suburban 5.3l vortec LC9 flex fuel motor
Has problems starting in the morning when it has sat overnight. Runs good when it starts and will start all day with slight delay until I park it again for the night. The fuel pump does turn on, and while running has 45 psi. Ignition on, engine off, has around 60 psi. These numbers are from after I have already started it and drove to school.
When I say it has to crank for a long time I mean minutes of straight cranking, it will stutter and almost start then die. This morning I had to use starting fluid to get it started. I live in California, it doesn’t drop below 30 degrees where I’m at.
No codes or lights on, besides a CEL for bank 2
below efficiency (which doesn’t turn on with my AFM disabler in)
First my problem was stuttering while under light acceleration 1500-2000 RPM range. Now the stuttering has almost completely stopped and hard starting has taken its place.
These problems appeared after I fixed several broken bolts on both sides of the exhaust manifold, sealing up the leaks. I also put in new engine mounts if that matters any.
I apologize if this is not enough info, any help is appreciated.

oldchevy

Welcome from Florida. Sounds like you have a bad check valve in the fuel pump assembly. It is letting the gas bleed back into the tank when it sits. You can replace the fuel pump or add a check valve in the fuel line near the tank.

Rednucleus

Try keying off & on several times to run the fuel pump and prime the system before trying to start - if that fixes it go with Old Chevy's diagnosis - AND Welcome to Chevy!!
Red

tankmaster909@gmail.com

I tried that this morning, cycled the key about a half dozen times for 5 secs each. Started up first turn but still some extended cranking. This is a great improvement from the last couple days. Sounds like I’ll be dropping the tank soon. Thank you!

tankmaster909@gmail.com

I think this may be my problem. Although I do have a question. The fuel rail is not supposed to stay pressurized for long period of time right? So when the truck turns off it will back flow and eventually reach 0 psi but still keep some in the lines so it doesnt take much to pressurize correct ? So my problem is that it has to fill the lines AND pressurize ?

oldchevy

The check valve keeps the gas from going back into the tank so the pump doesn't have to refill the lines. If the pump has never been changed you should change it before it stops working and you get stranded. Don't buy a cheap aftermarket pump as they don't last. Either buy AC Delco or Delphi, they cost more but are worth it considering the job it is to change it.

Rednucleus

After key on you say 60 psi engine off - how long does it take to drop back to zero once pump stops?

tankmaster909@gmail.com

it takes quite a bit, atleast for a minute I watched it and the pressure was going up slowly. Although I left the gauge plugged in for an hour and when I came back it was at 0 psi. I’m guessing a slow leak?