From reading this forum it seems most likely to be the Crankcase Position Sensor, if I describe the problem hopefully somebody can confirm.

DETAILS

On a warm sunny day a week or so ago the car was parked, I went into a shop and then starting the car the car starter motor would turn perfectly but the engine would not fire. After several minutes it turned and fired with no hesitation, no hestitency a completely normal fire after about 1.0-1.5s of the starter motor turning it. This happened again at the local supermarket. From cold it is always ok. I found this really puzzling because my experience of hot starting has either been fuel vapourisation in the lines with too little fuel, or flooding with two much fuel, both of which lead to a hesitant or weak fire/die situation, this is either 100% no or 100% go.

A couple of days I go I coasted down to a t-junction there was a soft thud and the dashboard lights came on, engine had died and I had to put it in neutral to roll it into my drive which it half managed and I had to push it 10 feet slightly uphill which took a great deal of effort.

On Sunday it died again on a busy highstreet I had to wait 20 minutes for it to cool down enough to start on double yellow lines feeling like a right idiot. It started again and 1 mile later died going down a hill and I managed to pull in but unfurtunately blocked someones drive and waited another 20 minutes for it to cool down hoping the owner would not want to get in. Finally I got it to my father in laws house where it is still parked while I went home in a £299 15 year old Renault Clio which is falling apart but still can be more guarranteed upon it seems

The C class is going to be booked into the garage today.

What strikes me is that from reading this forum it seems this problem has been going on for a long time and still it is happening. Why do Mercedes not swap this part out for a more robust part when cars are being serviced ? As well as being inconvenient and embarrassing it is also quite dangerous. My C class is the old C43 with wide tyres and heavy V8 engine and when it dies it requires a fair amount of muscle to get it to the side of the road with no power assistance after you have put it in neutral before losing too much speed. I was OK but my wife might have been stuck right in the middle of the road. Not good at all.

Anyhow, I will see if it is this part, I just hope it is and not something like the ecu !

All thoughts welcome

Regards

Andy

 

Yep, sounds like the crank position sensor is failing.

alot of people have a big enough problem paying for scheduled servicing (and I agree, it can be quite expensive at times) let alone replacing additional components because they have known faults that can occur in a few vehicles

 

Many thanks, it was the CPS as expected.

Prices are expensive in the UK so the price for the part was over £70 and the cost from the main dealer totalled £230. Oh well, they have cleaned it as well

Regards

Andy

 

Quick tip for those embarassing times you are stuck in an intersection. Keep a can of brake cleaner in your trunk...When the crank sensor overheats soak it with brake clean which will evaporate fast and cool it off enough to at least start it and move it out of the way. Dont expect this to be a permanent fix though, when you have to do this consider it the last resort before replacing the sensor.

 

Great tip....thanks! I don't know If I'll keep a can in the trunk but since I live in a Metro area auto parts shops are about every two miles (if not less!).