muleears

I know this is a common problem and we have tried the common fixes. Replaced all the lines and O rings, fuel thermo, banjo/check valve on back of IP and O rings on prefilter. No luck. Car starts fine when cold, VERY hard to start when warm. I can see large amounts of air in some of the fuel lines while the car is running. See this link: http://detali.ru/cat/oem_mb2.asp?TP=...SGR=120&SGN=04

In the second diagram fuel lines 74,56 and 119 appear to be about 50/50 air/ fuel. Line 32 is empty a few seconds after shuting off the car. Other fuel lines drain slowly as car sits after shutoff, but seem to slowly refill as car cools. Car does not leak fuel.

Car runs OK, hesitation on acceleration, I guess do to the air.

I have posted this on another forum and gotten some good ideas, I am just looking for a different set of eyes.

My next steps are: Replacing O ring on shutoff valve (if not the valve itself) replacing the K40, replacing the fuel pump.

What do you folks think?

Ausmbtech

There is a MB retrofit kit for a external fuel shutoff valve and one way check valve (at fuel tank) which helps solve this fault. I have successfully retrofited the kit to a C250TD which still had air in the lines after i had fixed all the fuel lines. I can get you the part number tomorrow.

Apart from that, does the air appear to originate from fuel line 74, 83 or 32 and which direction in the air traveling in these lines after shutdown?

Also try holding 2000-3000rpm and checking which hoses have visibal air in them, there will be some.

muleears

Sorry so slow in responding, been out of town. After replacing the O ring in the prefilter with the proper one, it appears I have solved my starting problem. I still see some air in the lines and the car hesitates upon hard acceleration but otherwise runs good. I may try the retrofit if you post the part number.