Hard Hot Start

I've got a 5.7L TBI (1995) that has an odd problem that I've been trying to diagnose and correct.
On a cold start, the truck starts fine. Drive it till it's hot and stop for
~30 minutes or less, it starts right up.
If you stop for longer than 45 minues or so, it will start right up.
If you stop for 30 to 45 minutes or so, it will start then immediatly die. You can crank and crank and crank and crank and it will eventually start, run rough for a few seconds, then idle fast and run fine. Stop it immediatly again & it will start OK.
I did notice that if I turn the key on and off about 10 times (letting the fuel pump relay come on for 2 seconds) after it won't start, it will then start right up without the crank, crank, crank.
Any thoughts? I've had a new fuel pump, filter, relay, etc. during the past 5 years that I've been trying to diagnose and correct this problem.
ANy suggestions or thought are appreciated.
Dave
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Are you in the habit of "topping off" when you get gas? I had a similar problem on an '87 Toyota and finally found out that I had flooded the evaporative emmisions canister (aka the charcoal filter). You might be able to test this by disconnecting and plugging the hoses to the cannister and see if the symptom goes away.

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wrote:

I think it is a combo of two things here. First is has a bad check valve in pump that lets pressure drop off when off and then because of this the heat flashes fuel in line to vapor and vapor locks the line when engine is hot which cycling the pump several times clears. You could replace pump or you could try insulating fuel line if you do not want to drop the tank to change the pump. ----------------- TheSnoMan.com
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On Tue, 28 Aug 2007 07:48:28 -0400, SnoMan wrote:

Huh? "Any thoughts? I've had a new fuel pump, filter, relay, etc. during the past 5 years that I've been trying to diagnose and correct this problem."
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On Tue, 28 Aug 2007 20:33:47 -0500, The Nolalu Barn Owl

I have seen new bad pumps and they do not live long if you run them low a lot. Might do a fuel pressure check running and when it shuts off but I do beleive it is a vapor lock problem and low fuel pressure will aggrevate it. A few years ago I talked to tech in a GM dealer thaty told me a story about a vapor lock problem on a 2005 car. It would not start hot after sitting 5 or 10 minute but would after 45 minutes or so. GM sent to engineers down and said it could not happen. He proved them wrong because when he packed fuel line under hood in ice/snow it had no hot starting problems. GM bought car back. ----------------- TheSnoMan.com
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Welp, since it might be a problem finding ice and snow right now, I think the OP would be better served investigating an evaporative purge problem as Ed H suggested.
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On Wed, 29 Aug 2007 04:52:45 GMT, aarcuda69062

Snow maybe but not ice or cool water. The point was tech cooled line to prove that heat was causing gas in it to boil and vapor lock. ----------------- TheSnoMan.com
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Or maybe the snow/ice was also applied to the evap purge line (they usually run right next to the fuel supply lines) causing the vapors to condense in the lines and not flood the engine.
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On Tue, 28 Aug 2007 22:17:06 -0400, SnoMan wrote:

problem.">"Any thoughts? I've had a new fuel pump, filter, relay, etc. during the

PARTS.
Listen -- then reply. I have a boss like you. He only listens for the other person to stop talking so he can jump in and say what he wants (whether it is related or not).
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On Wed, 29 Aug 2007 21:11:17 -0500, The Nolalu Barn Owl

THis is why I said to do a fuel pressure check and check for possible vapor lock issues too. ----------------- TheSnoMan.com
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