c220 diesel - fuel pressure to start?

[boolabang]

Hi all,

Have an odd problem with a C220 Diesel, won't start when cold unless easy start is sprayed into inlet, it will then start and run absolutley fine for hours - But once stopped will not re-start even when hot.

Believe its fuel pressure related just wondered if anyone knows what the fuel pressure should be when cranking?

Have checked and its only 50bar don't beleive this is high enough?

Have already changed low pressure pump (On front of head).

Not sure what to change next, any ideas?

Thanks
Wayne

 

[Alex Crow]

hello and welcome boolabang, you have come to the right place. firstly the cdi ecu needs to see 120 bar before it will fire the injectors. the most common cause of this fault is injector leak off, so just pull the pipes and watch them, if it is this it will usually be obvious which one is at fault. second likely are the o-rings on the control valve on the rear of the rail, just unbolt it and check them. good luck!

 

[MB Service Centre]

Yeh as above mate

 

[wullyuk]

This very fault was mentioned by the AA guy i had today word for word.

He said he seen quite a few CDI's with the fault you are stating and the point about easy start.

He did say the problem was with the High Pressure pump feeding the rail.

 

[Alex Crow]

i wonder if we have been a help to wayne, he was last on the forum at 9:18 pm this evening so has probably seen the advice. hope he comes back to say if it was useful.

 

[boolabang]

hello and thank you for reply's would a o ring fault on rail result in a leak of fuel, my fuel rail pressure is at 50 bar a lot lower than it should be 120+ surely that would result in a vbad leak.
checked leak off from injectors with kit seems fine all the same checked on another vehicle which starts ok for comparison
i am thinking possible high pressure pump worn not producing enough pressure at cranking speeds
any ideas thanks wayne

 

[MB Service Centre]

Dont jump the gun with hp pump< check it out correctly< remove the leak off and clamp it up, turn engine and you will prob find more fuel coming out of top of the inectors, there should be not much coming out at all, if there is thats a place to start with your pressure loss

 

[Alex Crow]

second likely are the o-rings on the control valve on the rear of the rail, just unbolt it and check them. good luck!

as mb service center says, DO NOT CHANGE THE PUMP until you can be sure it is at fault, there are other more likely things to go for.