Rough starting 5.3 GM V-8

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I have a 2001 silverado 4x4 with the 5.3 V-8 that is hard to start some times. Changed out fuel-pressure regulator, helped some then checked pressure on rail and was fine so pump must be ok. Also changed out fuel filter. There was a service bulletin about sulfer buildup on fuel pump and to use gm fuel cleaner in gas. Has anyone else had this problem? I bought the truck new and plan on keeping it a while, only have 64,000 miles on it.
 
Is it rough starting hot or cold. Cleaning the throttle body can help and a big bottle of Techron fuel system cleaner. It's about the same thing as the GM stuff I think. It cleans sulpher off and cleans injectors.
 
See if you can find some gasoline there in Iowa that does not contain Ethanol.

Think you still have a choice there unlike many other places.
 
Do the Seafoam in the power brake booster routine & run some Redline SI-1, Amsoil PI or Techron in the gas. Rev it up also.

Change the plugs & air filter too.
 
Change the inline fuel filter on the drivers side frame rail unless that is the one you changed

Clean the throttle thoroughly with TB cleaner and a rag

Clean the MAF with electrical parts cleaner, see if that helps.

evap solenoid is stuck or clogged

check the idle air control valve, clean it if dirty. it's mounted on the throttle body.
 
The at times is when it sits overnight, just being driven or a couple times in a row then starts fine then next few times.
No codes yet. I don't drive it everyday either. It could be the ethanol but I can run E20 in my 04' malibu work car with no problems. The in-line filter was the one I change. I look at the plugs and other suggestions when I can.
Thanks guys
 
Does it start OK if the fuel pump is cycled a few times before starting?

I once had an '02 company vehicle (it was with a 4.3L, but still kinda similar) that had the reg. swapped out trying to fix a fuel pressure bleed-down while sitting.

The new reg. didn't fix it either, turned out to be a fuel pump that had been replaced a a year or two before was bleeding down but would work fine if it was primed up first or finally started after cranking it a long time.
 
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Here is a test for you. For now on prime the engine 2 or 3 times before starting. In other words, key on/engine off so the pump runs to build pressure. If doing this stops the problem than your fuel pump is more than likely going out.
 
I think you said you changed the regulator which is an issue on those engine but so is the fuel pump. There is a check valve in the fuel pump which holds pressure in the rail. You need to see if the pressure bleeds down over night. Someone also suggested priming the pump by cycling the key several times. This may help you pin point if it is a fuel pressure problem.
 
It starts when the key is turned on/off a couple times, so more than likely it'll need a fuel pump before winter.
Thanks for the help guys
 
I've had the same problem for the last three years with my '01 5.3 with 53K on it. Mostly a hard start overnight. I need to cycle the ignition 2-3 times to start.

Its just the relief valve stuck open in the fuel pump. The fuel pressure is great but drops to near 0 psi when the engine is shut off. The systems is supposed to retain around 6 lbs. of fuel pressure at all times. A mechanic buddy said to change the fuel pump only if I find cycling the ignition annoying.
 
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