I have a 2006 r350 with approx 80,000 mi. Last November had the balance shaft repair done at the local dealership. We took a 2000 mile round trip Christmas visit to grandmas house and on the way home first experienced the start issue. After a day and a half on the interstate, we stopped for gas and lunch. After filling up with gas we stopped to have lunch. After the car sat for 30 mins. While we ate it wouldn't start. It would crank, fire and then die. After several attempts to start and about an hour on the phone with customer care, tow company and rental car agent, it fired and ran. We drove the rest of the way home with no problems. Since then we have had many no start issues where the car will fire and die immediately or just crank and no start. The car has been back to the dealership many times and the following parts have been replaced. Fuel pump, fuel pump relay, and crank position sensor. Still having the starting issues. The problem seems to occur more often after filling with fuel. On the last occurrence, the car would crank and not fire. I opened the gas cap and opened the steel flapper and there was a release of pressure. I couldn't tell if it was positive or negative pressure but there was a definite equalization. After that the car cranked twice more without firing and then started, however it was a rough low idle start. I had the vehicle at the dealership this morning for a short test and no codes were stored. The tech also did a fuel tank leak test and the car passed with an actual pressure loss of 4.1 hPa. I went back through old records and the charcoal filter canister was replaced in 09 when the car had 40000 miles on the clock. Does anyone out there have any ideas what may be causing my problems? Fuel system or balance shaft (cam timing) issue? Please help.

Another no start today. Tried the gas cap with no luck this time. Pulled and replaced fuel pump relay and car started. Car had less than 1/4 of a tank of gas this time. Has been about a week and 300 miles since last no start episode. Took me about 20 mins of trying to get it started. Anyone out there have any ideas?

Car has died twice now while driving in town. Dealership says we need a new engine control module. $3,000+. Unbelievable.

Start by replacing the crankshaft position sensor, common failure and leaves no trace.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.

I'd try to find a good, used part before I shelled out $3k for a new one. With that said, I agree with above post. I would have at least one more look at the crankshaft position sensor before I bought into the computer replacement.

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Jim

Crankshaft position sensor was replaced in March. Issue still progressively got worse after the replacement.

Can you tell any difference cold start versus when it is up to temp?

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Jim

Used to be when it was warm which is why we chose to replace the crank sensor. Now it is either hot or cold. Used to happen more with full tank of fuel. Now happens with any amount of fuel in the tank.

OK, first the bad news. Your dealer may be correct about the engine ECU being the problem. The good news is that there's a simple voltage test that they can do to be sure. Keep in mind that the no-start must occur while the test is being performed.

Ask them to look at document LI54.21-P-052569. It concerns hot-start issues on M272 equipped vehicle produced from 11/2006 thru 5/2007. It's possible they've already done so, but it can't hurt to ask. In my experience, it's a rare failure. I've only see it happen a couple of times but it's worth looking into. Good luck and let us know what happens.

Dealership installed new ECU. Called today and said car is ready to pick up. Wife went to pick up car and had no start at the dealership at pick up. She said the Service Manager was speechless. She is back in a loaner, not sure what they will come up with next. Does anyone know how the crank position sensor reads the position of the crank shaft? Is there a sensor or magnet on the flywheel that can fail?

Nothing on the crank except a "missing" piece of steel or a steel nipple. What was the source of the crank sensor that is currently installed? If it is not a MB part I'd be suspect.

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Jim

It was done at the Mercedes dealership. I assume it was Mercedes. I will ask.

ELoomis
My 06 r350 is doing the same thing and know one seems to be able to figure it out. What did you do to repair yours?

Here is something:

http://repairpal.com/mercedes-benz/r350

It comes comes down to the CAM Sensor

Best of luck,

Martin