E350Cdi - Bleed Fuel System of Airlock

MrGundam

Active Member
Joined
Jan 30, 2021
Messages
143
Location
Hampshire
Car
2012 C207 E350Cdi
Morning all,

So last week I did a bit of work on the fuel system by replacing a hose going to the fuel filter, as well as having to replace the injector return line. This meant having to remove the metal fuel pipes to the injectors to reroute the return hose correctly.

After priming the pump a couple of times the car started up and I took her for a 5 min drive, checked no leaks and hoped that was that. Next day and it struggles to start first time and usually starts second time around so I am assuming some kind of air lock in the system.

Is there a method to bleeding the system? I would need to run the engine with the bat wing off to get to the union nuts and kind of reluctant as may get a load of error codes then due to MAF sensors being unplugged etc. Or will the air lock eventually work itself out after a longer motorway drive?

Thanks
 

mersum1es

MB Enthusiast
Joined
Aug 9, 2012
Messages
1,822
Location
Finland
Car
W212, C219
Usually there is no airlock in system except injectors itself. Now when you didn't touch injectors, I doubt they have air lock problem, especially when it started first ok. Thats reason why injector changes are recommended to do one by one, runing engine in middle. SDS can perform bleed for injector, but you can try it at own risk by flooring gas pedal properly.

Start problem is usually due to leak somewhere, but since OM642 has primed system a leak (or moisture) should be seen if leak is severe enough. Double check all hose connections you made (inc T-piece seals etc), and also electrical connectors if you opened them.
 

KWER

New Member
Joined
Apr 14, 2017
Messages
17
Location
Surrey
Car
E350 CDi W212 Estate
Morning all,

So last week I did a bit of work on the fuel system by replacing a hose going to the fuel filter, as well as having to replace the injector return line. This meant having to remove the metal fuel pipes to the injectors to reroute the return hose correctly.

After priming the pump a couple of times the car started up and I took her for a 5 min drive, checked no leaks and hoped that was that. Next day and it struggles to start first time and usually starts second time around so I am assuming some kind of air lock in the system.

Is there a method to bleeding the system? I would need to run the engine with the bat wing off to get to the union nuts and kind of reluctant as may get a load of error codes then due to MAF sensors being unplugged etc. Or will the air lock eventually work itself out after a longer motorway drive?

Thanks
I thought these were self priming. When I changed my OM642 fuel filter I just topped up the filter popped the sender unit back in the filter and the engine fired straight away.
 

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