Occasional slow start

[mackguy]

Hi all,
Picked up our 99 Suburban last Monday, and driving around some just to make sure everything is good for our trip next weekend.

I have had a few times it took a while of cranking to get going, but once running it runs splendidly. Most of the time it fires right up, but had 3x where it takes a while of cranking.

Cranking is strong, so not a battery/starter issue. It doesn't seem to be an overall fuel or spark problem since it runs great one started.

From reading I've done here and web search fuel pressure regulator seems most likely.

Thoughts?

I found a write up on replacing the fpr on a 454 but couldn't find one for the 350, anyone have that handy?



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[SixSpeedSS]

The FPR is inside the intake plenum on the 5.7L Vortec. It is mounted to the side of the Spider manifold itself.

 

[SAATR]

I would run a gauge from the Schrader valve on the fuel line up the cowl and tape it to the windshield. Then drive it like that. Pay attention to the pressure at startup and while driving. If it has low fuel pressure while starting, you may have your answer if it is leaking off slowly. If not, look elsewhere. These engines like between 55 and 60 psi.

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[mackguy]

OK, I got a FP gauge and checked it last night.

Key ON, engine off, goes right to, and holds right at 60psi.
Key Off, drops down to 40psi within 10-15 min, down to about 20 after 1.5hr or so.

Engine running at idle 50psi
Engine running anywhere above idle, pretty much 60psi or a tad higher.

All 0 load just sitting in the garage.

 

[SAATR]

OK, I got a FP gauge and checked it last night.

Key ON, engine off, goes right to, and holds right at 60psi.
Key Off, drops down to 40psi within 10-15 min, down to about 20 after 1.5hr or so.

Engine running at idle 50psi
Engine running anywhere above idle, pretty much 60psi or a tad higher.

All 0 load just sitting in the garage.

Sounds good. Now all you have to do is drive with it hooked up until you can reproduce the no start condition. That way you can check to see if you have proper fuel pressure when it isn't starting and either verify the cause or eliminate it from the list of possibilities.

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[mackguy]

Would need to get an extension hose for the gauge to get it visible. Do the numbers I posted at least sound within range of what they should be? Only thing I wasn't sure about was leak-down speed.

 

[Velislide]

I've heard lots of mixed opinions about fuel pressure leak down speed. Mine leaks down extremely fast, probably 10 seconds, but my truck runs great.

 

[SAATR]

Yes , they are in the proper range. The idle pressure sounds a little low, but you have no running issues, and it could simply be gauge calibration.

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[mackguy]

Who knows when the fuel filter was last replaced too, so that may not be great.. but runs fine and getting 20mpg so can't be too bad..

 

[SAATR]

My 97 gets 15 if I'm lucky. I'm chipping away at that presently, but I don't expect 20 unless I do 60 everywhere I go.

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