Thread: Vapor lock after parking.

So I have my 2000 Pontiac Grand Prix gt. It seems to run great other than a slight leak on the oil level sending unit. The issue I continue to run into and can't seem to pinpoint is why it constantly has trouble starting once it sits for a little while. If I started it from completely cold it fires right up without a problem. However if I go to say a grocery shop for a few minutes and I come back out and the engine has gotten above say 155 degrees it has a sputtering start and over 165 or so it won't start. I know it's a fuel issue since I bought the fuel line pressure gauge tool however I'm not sure if its the fuel pump or some sensor. The only way I can get it up and going is to basically stomp the pedal to give it enough fuel pressure. I'm not sure if its fuel pumps because I'm on pump number 2 right now and if anything this ones issue is worse. I have a rather large sound system that's grounded in the trunk. I can't see how that would affect it but I'm kinda baffled. Any help would be appreciated. I don't want to be late to an important event because of this.

Yup it's not the filter I tried that back during the summer and it didn't help. It's been replaced twice in the past 3 years

Hmm perhaps. That would make some sense but it wouldn't explain why it shudders below 165 and I've had it fail to start below 160 on a hot summer day

Originally Posted by dsmuts

You aren't getting vapor lock it can't happen on a fuel injected vehicle

Lol not to be mean here but that's completely incorrect vapor lock isn't eliminated by a fuel injected vehicle. Now in most cases it's gone but I have had vapor lock on two Chrysler town and country vans. Both of which are fuel injected, vapor lock is usually corrected by the fuel pump being ore pressurized before the system kicks on. However if the pump still wasn't creating enough pressure then vapor lock would settle back in.

As for the other questions, no it is not an air issue I have a very clean intake and filter. Like I said I have the fuel pressure testing tool for the fuel rail and my gauge is showing no pressure when it won't start and a very low pressure when it's sputtering.

As for codes being thrown no there are none accept for a low oil level light being thrown due to the slight leak in the houseing for the oil pressure sending unit.

Any other ideas guys? Cause I have been trying to wrap my head around this for months

Could it be the fuel pump getting hot and quitting because its might be going bad?

No matter how clean your intake/air filter is, you'd better check your throttle body. My 05 GT would start great cold, but almost stall out and occasionally would, when starting it with the engine warm. I took off the intake and the throttle body appeared to be clean. Unbolted it and looked at the opposite side (the side facing the UIM or supercharger on L32/L67 setups), and it was caked black with carbon buildup.

I just took some carb cleaner, sprayed it down and wiped/scrubbed it repeatedly until it was squeaky clean, and I've never had startup issues since.

Originally Posted by nik12937

No matter how clean your intake/air filter is, you'd better check your throttle body. My 05 GT would start great cold, but almost stall out and occasionally would, when starting it with the engine warm. I took off the intake and the throttle body appeared to be clean. Unbolted it and looked at the opposite side (the side facing the UIM or supercharger on L32/L67 setups), and it was caked black with carbon buildup.

I just took some carb cleaner, sprayed it down and wiped/scrubbed it repeatedly until it was squeaky clean, and I've never had startup issues since.

Had the whole top end off of the engine this past summer when my dexcool decided to eat through my gaskets And spew all over my driveway, while i was at it i cleaned the very small amount of carbon that was there. The issue was happening before that.

As for the fuel pump going bad it's possible but I doubt it since I have already swapped the fuel pump out twice first time to fix the fuel gauge and the second to try and resolve this issue. Fuel pressure regulator seems possible but it runs fine once it's started so I figure that can't be it. I'm thinking icm more and more