Hot start problem
 

Hello, had this issue with my car for quite awhile and while it hasn't bothered me that much, thinking about selling the car soon and want everything to be 100%. If I shut car off and restart within 5 minutes or so, fires right up. If I shut it down, leave it sit for say 15 minutes or more, the car will sometimes crank over for maybe 7-8 seconds before coming to life. The car always fires up strong when cold. Runs strong, no codes and I do occasional boost leak tests.

Could this be a maf sensor issue? Or is there a coolant or oil temperature sensor that could be causing this?

I have searched quite a bit and not found a whole lot. I recently replaced the fuel pressure regulator based on some thread I dug up on renntech.

Any help here would be greatly appreciated!

from the land of a thousand guesses...when was the last time you checked your battery? how old is it? could also be an ignition switch problem.

The battery is a little over a year old so I don't think that is the problem. The starter cranks over just fine whenever I turn the key, just takes longer than it should to actually restart after the car has been sitting awhile.

Mine does the same thing and has done for the entire time I've owned it (2+ years). No vac/boost leaks, no codes. Car runs perfectly otherwise. I've just chalked it up as a nuance of my car. It really doesn't bother me anymore.

I ordered a new maf, will update on results...

that was a great reply. wilson pickett loved it.

Going MAFless didn't change the issue at all for me. Maybe a new MAF will work for you.

Think I have finally found the problem - fuel pump relay! Car fires up like it should all the time with jumper in place of the relay

Thanks for the update. Maybe I'll try that too.

Put a fuel pressure gauge on it and see if it's holding pressure with the car shut off. Likely it's the check valve inside the fuel tank has failed and isn't holding pressure in the system. This is the reason it starts with the fuel pump relay jumped.

It should hold at least 2.75 bar (40psi) for quite a while. An hour or so after shutdown.

996t does not prime the pump at key on like a 997t does (and they only do it every 3rd time or so). It cranks forever because it's trying to build pressure in the system. Probably runs bad for a second or two once it does fire also?

+1 Found this to be the main cause in 996tt's with the warm crank issue, thing is that checkvalve has no oem part number and is a bit messy to diy...

With 997tt's its almost always the starter, those things seem to have a life of about 4-5 years in hotter climates. They start fine when cold, but stop at a gas station for example and you need to crank it 2-3 times to fire the engine: only explanation would be it drops resistance badly when all heat up. New bosch starters are less than half the new oem price and fixes the problem for good.

Good luck.

Reviving this thread. I bought OP,s car back in 2017. This problem persists. I suspect the fuel tank check valve. Any good articles on diy? Or, anyone added a check valve else where?
Any help appreciated in advance.
Thanks
Mo

It's doesn't make sense that's the check valve is the problem if it starts when cold and not hot.If it's loosing pressure then it would be hard to start when cold too.
I believe your problem is in the ignition system where the ECU isn't recognizing the engine rotation.
Or the fuel pump is old and drawing to much current when hot. Check the connector for evidence of burning.
My 02 fuel pump died a while ago and I replaced it with an aftermarket pump, not the OEM assembly. Since then I've had the opposite problem when the car sits for more than a couple of days I need to cycle the ignition switch a few times to build pressure to start. And yes the pump does prime because I've seen power at the fuel pump connector.
Recently I found the Venturi system isn't working and it's out of gas below 1/4 tank and the basket is empty. I need to find out why.

The thing is, if I start it right away when hot, it will fire right up. It’s only after it sits for a bit. Maybe 5 minutes or more. I’ll hook my fuel pressure gauge up to it.

How does it start after a few days of sitting?
I pulled my fuel pump last night and crimped clamp on the fuel pump is not tight enough. I'll put a jubilee clamp on it and see.