efonz

I have 126,00 miles on an 05 E5 and the car will not start sometimes. It is difficult to explain and diagnose in my opinion because I cant figure out a pattern as to when it does and doesnt start.
I was pretty sure it was the crankshaft position sensor because the car seemed to only start after cooling down and the sensor as I understand heats up loses contact and then resettles into a closed
circuit when it cools but I replaced it and the car seems to start with no problems only when it wants too, cant say it another more specific way unfortunately.

I have replaced or checked:
crankshaft position sensor
brake light switch
charged battery in trunk
check AUX battery

Also and something I am sure is related is that recently I would say 2 weeks ago I noticed that on uneven ground I would not be able to shift from drive into reverse the shifter would not allow me to go past neutral.
Later I noticed I could shift into any gear without pressing the brake. This morning the car turned on no problem but would not allow me to shift out of Park, so I turned it off. It wouldnt start the next few times I attempted
to do so, although I am sure it would start if I went out there right now. I have opened the gear shift selector by removing the console but I am not sure what to look for. Any ideas as to why it turns on at random? I am able
to turn the key all the way to the right and the lights work and everything but its almost exclusively a no crank no start unless it starts I think once it cranked for a half a second but never started. Any advice I would appreciate.

LexBrett2

How can you be sure this is NOT the Crankshaft Position Sensor (CPS)? CPS problems may only occur intermittently, and you may have the problem even without the code p0335. I found the hard way these cars are very sensitive and prone to CPS problems, changed my CPS with a sensor from Advanced Auto and then that failed and I bought a Bosch and things seem okay now. The CPS is a doable DIY, but definitely requires the correct tools, a lot of time, and a lot of patience

Bahnstormer

Fuel pump going bad?

efonz

I am thinking the same thing but the last month the Fuel tank and Fuel pump assembly were replaced. The tank was done by Mercedes under warranty and
had the pump replaced at an independent shop (currently waiting for reimbursement). The guy who serviced the pump isnt who I normally go to and I have doubts
about his work but the pump was replaced a day before the tank was inspected and replaced by Mercedes so I am and have been assuming that they would have
noticed something wrong with the pump when they replaced the tank and tested for functionality. It does seem like a fuel sending issue but it could be so many other
things to be honest its overwhelming. I ordered an icarsoft MB II and it will be here this thursday so im hoping that it will lead me in the right direction. How would I know
or verify if the fuel pump is sending fuel when the car doesnt start, remove rear seat cushion? what am i looking for the actual fuel lines or just listening to hear the pump
turn on?

efonz

Well I bought a bosch crankshaft position sensor from pelican parts installed at first I thought I had remedied the problem but no because the next day same thing no start no crank. I dont think it needs to be replaced again as the symptoms before I replaced it and after are the same. Also I read that a faulty crankshaft position sensor would result in a car that cranks but will not start and a camshaft pos. sensor is the no crank no start. can anyone confirm this?

Also is there a relay associated with the fuel pump, can anyone tell me where it is?

Daniel Olivares

I had the same problem. It is difficult to know if it is the Fuel pump relay you kind of have to wait until the car fails so you can test it. When mine died, I put the jumper wire and it still did not start. I took the rear seat off and removed the fuel pump cover. There was no sound with the pump. Checked the connectors and nothing. I got frustrated and lightly tap the pump and it started working. (This was with the jumper wire installed the whole time). Put the relay back on and the car has run fine since. It was odd because the pump is only a year old from the dealer (under warranty).

LexBrett2

At least in my experience, a bad CPS will cause the car to sometimes start and sometimes NOT start. Also, the car would die while at stoplight occasionally.

LexBrett2

Where you getting a OBD trouble code??

EuroDriverSD

Best thing I can suggest is to obtain a diagnostic at the dealer or someone with a proper STAR-DAS diagnostic scanner. I went through this exact same headache (minus the not wanting to shift gears - that sounds like a separate issue) on my '08 E350 last year. I had no check engine light at all but the car started when it wanted to (more difficult when warm) and on mine it turned out to be a fried throttle body.

efonz

I removed the rear seat and checked the connections that are on the drivers side rear seat. the passenger side i am assuming that is the actual pump and I am supposed to unscrew that huge *** thing right?

thanks for everyone's opinion I will keep all of it in mind. I just got the carsoft mbii in the mail and ill see what codes come up soon. The car started on two consecutive attempts since my initial post but since then i have had the negative cable disconnected so I dont know if tapping the fuse pump relay and re seating the connections under the drivers side rear seat actually did anything (one of the wires in the main connector appeared loose to me but im really stretching for an answer here)
I am going to get a new battery under warranty I just want to rule that out for sure 100%

C230 Sport Coup

Wrong thread.