ML 320 will not start in HOT weather

[KnicK]

My wife has a 1999 Mercedes Benz ML 320 with 64,000 miles on it. It will not start in the HOT mid-day sun. It will start first thing in the morning and at night. The battery is good. It turns over and runs for 2 seconds and then shuts down. I just had a fuel pump kit installed for $600 bucks !!! and it still will not start when the temp. gets to say 80 degrees and more. We live in the San Francisco East Bay area.
Could it be the fuel filter? A sensor, or maybe a fuel line? Any suggestions would be most appreciated.
KNICK
Email: gomatsfrosh@yahoo.com

[benzboyz]

maybe the fuel pressure has internal leakage, the regulator is builtin with the fuel filter. to be sure try to install a pressure gauge. the presure should not drop down below 2.5 bars after the engine is off, even after 30 minutes.

[benzboyz]

maybe the fuel pressure has internal leakage, the regulator is builtin with the fuel filter. to be sure try to install a pressure gauge. the presure should not drop down below 2.5 bars after the engine is off, even after 30 minutes.

[SOPRANOO24]

CHECK YOUR CRANK POSITIONING SENSOR. MIGHT BE GOING OPEN ONCE IT GETS HOT.

[tntadano]

I have the same problem with my 1998 ML 320. After driving it for a while (engine reaches normal operating temperature of around 80 deg C) and then turning off the engine for about 30 minutes to an hour, it will not start. this happens about once every five attempts to start. The engine does not appear to be getting any fuel (like a vapor lock). After trying to start it a few times and then letting it sit for 5 to 10 minutes, it starts up without any hesitation. I always have to let it sit for 5 to 10 minutes after the first attempt to start it. Otherwise, it runs smoothly so I do not think it is a fuel pump or fuel filter problem. It could be fuel pressure. However, why do I have to let it sit for 5 to 10 minutes before it will start. And when it starts it is as if nothing ever happened. It does not cough or stutter. I do not think it is related to the environmental temperature but instead to the engine temperature (normal hot temperature of 80 deg C).

For your information, I had a "Check Engine" light caused by "Fuel Trim Malfunction in Bank 1 and 2 which I fixed by replacing the Mass Air Filter or Air Mass meter. No more error codes or check engine light however the start problem still persists.

Any help would be appreciated. I will let you know if I solve the problem.

[junkman]

I may be way off base here but I've had similar experiences with some domestic cars and 9 times out of ten it was a coolant temperature sensor. I don't know if this applies to the Benz system or not but it may be something to check.

[LhaitzSS]

You need a new crank sensor for sure. WOuld cost 120.00 bucks tops. Good luck.

[jmarenas]

OK< I have 170,000 miles on my ML 1999, SAME THING HERE!! Replaced the CPI, Fuel Filter, still does the SAME THING!!! WHAT GIVES HERE NOW ONE KNOWS WHY!!!!!!