I have a 99' ml430 that i recently bought. It had about 118,000 miles when i bought it and it drove fine. Currently it has 119,200 and it just started acting up. Here is the run down, I drove out of town for about a 1.5 hour drive and then it decided to shut-off on me while i eas driving. After trying to start it back up and realizing it was not going to start I waited for about 20 mins. then I turned the key and as if nothing had happend it turned on, no wierd idle or and funny noises. So on the way back home the next day in the exact same spot it died again. Did the whole waiting thing again and it worked, drove home for about 1 hour and 20 minutes no problem. a couple days later took it out for a drive and after a stopped at a gas station while i was driving home it did it again. This time i watched the temp. guage and it went up 3/4 of the way to its max. So can anyone on here give me a heads up on where to start looking for the problem or have an idea what it can be. Any info will be greatly appreciated THANKS.

Sounds like your dealing with a faulty crankshaft position sensor a common fault on 99's. After the vehicle cools down its starts again. Tim

My former 99 ML320 exhibited the same symptoms just before the fuel pump died...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

So the temp guage inside the car, where is it normally supposed to be at?
Because before the problem it would sit right on the 80 now its usally in between the 80 and the next line.

If you can take it to your maybe not so friendly Mercedes dealer, or any mechanic that can plug an OBD II diagnostics computer into the car and "talk" to the computer, chances are a fault code will be stored if it is the Crank Pos Sensor. I'm not sure that a failing fuel pump will throw up a code one these. Normally,, it doesnt. May cost you a few bux, but the money and aggrevation you save in trying to figure it out, maybe worth it.

Rick

Actually it is very unlikely that either condition will set a code. crank sensors almost never set a code. The only way they set a code is if they run intermittantly for a period. They usually just won't let the car start and because the controller doesn't see the engine turning it doesn't fault them.

It is easy to monitor the fuel pressure so if it isn't that then it is the other. BUT!! if the crank sensor doesn't show rpm the controller shuts off the pump so the test is useless for a no start. In that case you bypass the pump relay and verify pressure.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

i appreciate all the advice. thanks for everything. I replaced the CPS and so far its working fine.