Stahlroad

Hi, new here and hoping to get some collective wisdom (assuming any allroad owners are wise) . My 2005 will not start after sitting in hot temperatures. Here are the symptoms. Starts up great in the morning and funs fine weather it is hot or cold outside. But, turn it off and leave in hot Texas sun for 15 min or more and guaranteed not to start. The engine cranks normally but no ignition. Let it sit until evening and it will start right up. Reminds me of the days when you heard of such things as carbs and vapor lock. The engine light comes on after cranking for a while and throws some generic codes related to general ECU communication problem (but where?) The mechanics who have looked at it have all concluded that when the engine is not starting, there is a fuel delivery problem. Here's what we've done: (1) replace the fuel filter (no improvement) (2) replace the fuel pump (no better) (3) replace the crankshaft position sensor as this is the most common problem based on other forums. (still no better) I have ruled out the coolant temperature sensor since failure there would cause the engine to flood , not starve from lack of fuel. The fuel pressure regulator is producing proper voltage.
The engine runs very strong even in under the hottest conditions. Ergo, this problem with the fuel delivery, what ever it may be, affects only starting. Anyone have any ideas? what about the fuel relay? would faulty fuel relay affect only starting the engine? Vacuum hoses?

Thanks in advance for reading!

Stahlroad

I forgot to mention that this is the 2.7t version with automatic transmission.
Thanks

MrKid

Good luck with your problem...

YKallroad

I had a hot-start problem, but it was not able to crank (turned out to be a bad positive wire on the battery.)

Not helpful I know, sorry.

John535is

are there any other lights on when the starting problem happens?
I had a very similar problem, I too thought it was fuel (vapour lock for us old timers) then I realised the ESP and EPC lights were on. That results in the brake light switch failure. Just happened to start doing from hot starting which was just a coincidence.

With the poor starting, easy to overlook the other indicator lights. Another way to check is when it doesn't want to start, see if the brake lights are working.

something to try anyway.

Ottoman56

I have a 2001 allroad 2.7t automatic. Same exact problem. I did all the things you did plus the coolant temp sensor and the fuel relay. I can drive it to work with no problem. If I try to drive it to lunch, it won't start. But, by the time I am ready to go home at night it starts right up. My wife says we are saving money by me not going out for lunch!
I just noticed that you wrote this in August, did you figure it out? I would appreciate a hint.

NativeYardsMT

We have a 2004 manual 2.7 allroad. Three months ago it wouldn't start after driving through town. Now it has gotten worse, usually won't start after sustained interstate driving, so we figured a hot start issue. The one thing that is notable is we can always roll start it. It is now taking longer for it to start after failure, sometimes over an hour (in cool weather), but it always does restart. We have had Coolant temp sensor and Crankshaft position sensor replaced, and now it is stalling at stoplights in a snow storm when engine isn't even hot yet- no good! It seems like out issue is a little different than what I have seen, so any insight would be appreciated. Thank you!!

PetrolBear

No MIL?
If not , also check for fault codes. Without this it would be a riddle only.
You should check the throttle valve function. That small electric item works a lot and are prone to age around 200-250t km in any of nowadays cars. Just a hint.
SSP198 summarizes the engine managment system, very detailed. Google it out, download.

Ottoman56

I solved my problem. Mine was the injector seals. This makes sense if you think about it. The engine heats up and one of the seals that has deteriorated expands, so then when you try to start the car again the seal leaks. When the engine cools the seal contracts and no longer leaks. If you know where your seals are located and can get to them you could try this. With the motor warm and still running, spray a little bit of starting fluid by each injector seal. If the engine revs, then you have found your problem.
Let me know if this works

NativeYardsMT

We finally got our problem, which was stranded us more and more often, fixed. First we replaced the CTS (less than $100) - no fix
Then the Camshaft Position Sensor, a real bear to change. $455 later it still didn't fix the issue. Finally, we had the Crankshaft Position Sensor replaced. Sure enough it was cracked, and that has fixed us up and we are good to go. I hope this helps someone else out there