C270 W203 not wanting to start

[EdmundIJones]

Hi,

My C270 CDI is going through a difficult phrase where she just won't want to start quite often. She is turning over with plenty of vigour but just doesn't catch sometimes. About 60% of the time she starts on the 4-5 crank then other times (normally when warm) she will take 30-60 seconds of cranking to get running.

Now, I took her to an indi friend of mine yesterday afternoon who kindly connected his fault code tool but nothing reported but he did get the realtime values which we deduced there was not enough fuel preasure to start. We understand that it needs around 300bar to start properly but it was showing around 120-200 bar when cranking, as soon as she caught and started it was over 300 and up to 600 under reasonable reving.

He thouguht that the first thing to try was replacing the O ring at the back around the connection to the common rail or something before checking hoses and the preasure pump (or something)

Does this sounds about right?

 

[BlackC55]

The injectors will need to be checked for excess leak off first.

 

[EdmundIJones]

He had a quick look but didn't have his tools with him to take the engine covers off. He said he couldn't see any sign of leaks but couldn't be sure. He thinks he has a spare new O ring in his garrage and is going to look today and give me a call, then he can take the car and look at it properly.

I was just wondering if the preasure problem was a plausable.

 

[EdmundIJones]

I should have added that once the car is started it drives and idles just right without any any problems.

 

[BlackC55]

There is more than one "O" ring.

Does he know how to check the injectors for leak off?

 

[EdmundIJones]

I beleive so, he is a very well experienced technitian with at least 15-20 years under his belt, he specialises in porsche's but also works on Mercedes and BMW's.

 

[alexander patie]

the pressure needs to be 120bar to start, no more. as blackc55 says, the leak off will need checking IF the 120bar figure is not being reached. if it is cranking in excess of 120bar and still not starting look elsewhere.

 

[EdmundIJones]

Right, the guy had the car last night and replaced the O ring regardless, he says the engine bay is clean as it can be and there are no signs of a leaking injector but he didn't get time to-do a leak off test.

What I can say is that the car is starting better, not brilliant but it's starting withing 2-4 cranks which is a big improvement.

He is going to take it again in a week or so's time and do a leak off test and see what he can find with a bit more research.

I'll keep people posted on what happends.
Ed

 

[andymerc]

injectors very common fault ,internal leak you won,t see any signs of leak ,need to put test tubes in leak off of injector the faulty one will fill tube on turnover,dumps pressure into leak off.

 

[wardpaa]

Ed, My 270 had an issue if left for longer than 10 mins. Turned out to be a fractured rubber fuel pipe rubbing against the engine cover (Stealer fitted it last) where the filter is. After that was done by a specialsist indy starting improved significantly ( a hole in a pipe is never a good thing) but it still played up occasionally. Replacing a recently stealer fitted fuel filter cured the problem once and for all.
Take the engine cover off and see if you can see any air bubbles in clear fuel pipes on the low pressure side, especially where the exit pipe from the filter is, which is at the highest point.

 

[EdmundIJones]

Hi chaps,

Just and update on my starting issue.
My indi friend had the car from wednesday night through to Saturday afternoon and he worked on it in his spare time, he did the leak off tests and had a good poke around.

The result being:
2x new injectors, cylindars 3+4
Oil change and filter
Fuel filter
air filter
Gearbox drail and refil
A selection of other bits I can't quite remember and a O/S lower ball joint arm

The car now starts like it should and runs nice and smoothly. Very happy with it all now and it's got a new MOT to see it though for the next year.

I'm now a bit lighter in the wallet area but a lot happier than if I'd taken it to MB to get it all looked at and serviced.

Thanks for all the help and guidence. Again it seems the intial idea of injectors for the starting fault were spot on.

Ed