Extended crank when warm or hot on crate GM L31

[PlayingWithTBI]

What's your fuel pressure with key on engine off? Does it hold pressure or does it leak down after the pump shuts off?

 

[Fragment]

What's your fuel pressure with key on engine off? Does it hold pressure or does it leak down after the pump shuts off?

Fuel pressure is 61 KOEO, around 52psi after an hour of sitting, spikes right back to 61psi with key on, and idles around 55psi. This is with both fuel pumps I've tried, both spider units, and both fuel filters.

 

[HotWheelsBurban]

Fuel pressure is 61 KOEO, around 52psi after an hour of sitting, spikes right back to 61psi with key on, and idles around 55psi. This is with both fuel pumps I've tried, both spider units, and both fuel filters.

That's interesting, because my 99 Burb 5.7 vortec does something like this. I figure the FPR is a little tired after 198,000or so, and let's the pressure bleed down some. Holding the key in On so the pressure builds up in a few seconds, and it starts fine. The spider comes with a new FPR so I plan on doing all that stuff together.

 

[Fragment]

That's interesting, because my 99 Burb 5.7 vortec does something like this. I figure the FPR is a little tired after 198,000or so, and let's the pressure bleed down some. Holding the key in On so the pressure builds up in a few seconds, and it starts fine. The spider comes with a new FPR so I plan on doing all that stuff together.

The funny thing is my dad also has a 99 Suburban he’s had since new. We did the upgraded spider a few years ago around 160k, and ever since then his has done the same thing. His only does it every fifteen starts or so though, and only when warm.

The bummer for me is priming the fuel system like that, or just wiring the pump straight to 12v, does not alleviate the problem.

 

[96TahoeDoug]

Not saying that this is the problem with yours but hot starting problems can be caused by vapour locks in the fuel system. Fuel pipe in the vicinity of say, exhaust could cause it.

And just because it's only $8 put another fuel filter on it. I just went through this. God bless it was that easy fix. If it doesn't I'll owe you a hamburger.

 

[Fragment]

And just because it's only $8 put another fuel filter on it. I just went through this. God bless it was that easy fix. If it doesn't I'll owe you a hamburger.

You mean a third one? Ha!

Forgot to mention I replaced the tank when I did the fuel pump too because it had sat with bad gas for ten years. So the tank was clean when all this started

 

[Pinger]

What proves/disproves/alleviates (temporarily) a suspected vapour lock is swaddling the suspect area/component in rags soaked in cold water.

 

[Schurkey]

What proves/disproves/alleviates (temporarily) a suspected vapour lock is swaddling the suspect area/component in rags soaked in cold water.

Yeah, but you have to be smarter than the rags 'n' water.

 

[stutaeng]

@Pinger I don't think fuel vapor (such as a leaking purge solenoid valve) would cause a no-start. If you watch a video about GM EVAP systems, the pressures are REALLY small, somewhere around 2 mm of mercury = 0.040 psi. Besides, the compression in the cylinders is much higher. Are you thinking like a vapor-locked engine?

What does the compression ratio of an engine mean? 10:1 for example. Is that 10 atmospheres of pressure to 1 atmosphere of pressure? That's like 150 psi? I honestly had never wondered what the ratio was. I'm just a hobbyist, LOL.

Edit: looks like compression ratio is volume of the cylinder in the "down" down position to volume of cylinder in the "up" position...

 

[Pinger]

Yeah, but you have to be smarter than the rags 'n' water.

Ehhh?