Trouble starting when warm

[Jon_K]

Greetings,

First off I'd like to mention I'm driving a 97 TSi AWD.

So, I'm having a weird problem...My car starts up just fine when it has been sitting for a while and is cold. The problem occurs when I've been driving (usually after 10 minutes or so) and I shut the engine off for a few minutes. When I try to start the engine it will usually just crank but won't fire. Most of the time it will fire up after I crank it half a dozen time, or I let it sit for a while.

Like I said, this only happens after I've been driving for a while and shut off the engine for a minute or two. Other than that, the car runs beautifully.

Any ideas?

- Jon -

[Paul]

Mods?

Paul

[sbiggi]

Upgraded fuel rail? The metal/aluminum ones can get hot and vaporzie the fuel in the rail.

[Carl Morris]

My VPC setup does that pretty bad when it's hot. Other than hot bubbly fuel, my only other theory was that my temp sensor for the speed density setup was super heatsoaked making it run lean. I know it's lean, though, because if I add a bunch of fuel it doesn't do it so bad. So...I doubt you're flooding it.

[D Walker]

well without knowing the mods it hard to say, but there are a few things that can cause this on a stock-ish car:

FPR solenoid disconnected or improperly plumbed back in. Many cars will allow you to bypass this completely with no issue, but some(a very few) wont. The ECU takes into account that this is working, so if youve disconnected it for some reason you could have simply pissed the ecu off.

Fuel pump check valve going bad, or pump itself dying- this is really pretty common. Basically when the fuel is hot the check valve the pump wont hold pressure in the line, or if the pump is on its last legs it takes a second or three to pump the hot fuel. The thing many forget is that the fuel circulates from the tank to the rail and back, getting heated at the rail in the process, and takes that heat right back to the tank. After a bit of driving the fuel in the tank can be pretty damned warm. The warm fuel isnt as dense and the pump has to work harder to keep pressure up. Both of these are very simple to check with a fuel pressure tester.

The coolant temp sensor can also be causing this, but check the other things first.

If you have any mods it would help gretly to list them, along with anything you have checked and what results you observed.

[Jon_K]

Sorry about that

Nothing too fancy. Mostly stock accept K&N intake, 3" turbo-back, BOV, electronic boost controller

I've noticed since I posted this topic it has been starting up just fine lately. I think it has to do with the cooler weather up here (Ft Collins). I noticed on days that were 90+ degrees that that is when this was problematic.