W202 C220 Cdi Warm starting problem

[Melvin C. Yowser]

Good evening!

It's my turn to experience warm starting problems!

Originally it was a very occasional problem, but now it refuses to start every time the temp gauge is over,say, 60 degrees. This deterioration occurred without any underbonnet intervention from me! I've never experienced the car firing and then cutting out -the engine will always spin on the starter, but flatly refuse to fire. If I simply leave the car for an hour to cool down, it'll then immediately start at the touch of the key. The car always starts from cold, but I'm noticing that the car is taking longer to fire on the first start of the day.

I changed the fuel filter in September last year, several months before I experienced any starting problems. However, between April '07 and when I changed the filter I was regularly experiencing episodes of very rough idling. After the filter was changed this now happens much, much less frequently - I can't remember the last time it occurred. I've noticed the idle will still fluctuate very slightly when the engine is stone cold, but this isn't remotely as bad as the old rough idle symptoms.

The plastic fuel lines were very yellow, so I changed them all and the problem remains the same. When the engine is switched off, I can see diesel in the shortest plastic pipe that runs from the rearmost outlet on the fuel filter to a black plastic object behind it, drain away from the fuel filter so less than half the pipe is full of fuel. Does this suggest I've still got an air leak?

Any thoughts or suggestions would be hugely appreciated.

Cheers!

Melvin.

 

[Devonian]

most likely will be the crankshaft sensor. I understand you can get a new one via Bosch suppliers for about about £40.

 

[mister_cee333]

Perhaps one of your injectors is leaking. Have a leak off test done by a diesel fuel injection specialist, it should only cost an hour or so labour. I've had similar with the 2150cc engine twice, once a hot start problem, and once a cold start problem. Total cost for diagnosis, removal, repair and refit one injector was £185+vat. Apparently they're particularly prone to faulty injectors from 02-03 year.

 

[amb67]

At a guess I would say that you may have more than one issue here.

Was the fuel filter you fitted a genuine MB part?

From your description it sounds like you have a glow plug issue and a fuel pump/fuel line/air leak.

Finally, is the boot interior wet or show signs of water staining? The reason I ask is that the rear SAM units can become damaged by moisture and I have replaced quite a few that had caused poor running and starting issues.

I would get the current draw on the fuel pump checked out, it is not uncommon for the fuel pumps to fail intermittently.



I doubt that it will be the crank sensor, the sensors are Piezo solid state internals, they either work or they don't. Although the teeth on the reluctor ring may be damaged, but unlikely the cause of this problem.

 

[Melvin C. Yowser]

I'm delighted to report, after months and months of misery, successful warm starting has resumed! There's a black plastic cylinder with a plug socket bolted to the end of the fuel rail. Very limited space meant I had to remove it using an E8 spanner (difficult to buy separately, I found - Halfords only stock it a part of a set. After some extended internet searching, I found it available at www.awautomotive.co.uk - £8.23 delivered).
This black cylinder, which I assume contains the sensor that measures fuel rail pressure has three seals on it - two rubber and one plastic. Mercedes sell them together as a kit -Part Number: MA014 997 70 45. £5.82 including VAT. Problem solved!