OM611 fuel line O-rings and leak

[Crosscut]

I have an air in fuel problem.
This is a OM611, four cylinder, mechanical low pressure pump, no lift pump in tank

I've read in several places that there are 6 O-rings on voss connectors in the fuel system, I can only find 5:

1- top of the fuel filter
2- Low pressure pump in
3- Low pressure pump out
4- Low pressure fuel sensor (under intake manifold)
5- Fuel rail (at the back under the injector cover)

all the diagrams I can find don't really relate to my system.

I have changed all these o-rings (each one I have changed has improved the symptoms)
I have put on a filter without the water in fuel sensor and checked/remade the connections several times.
I fitted a new fuel filter to low pressure pump line.
I replaced the rubber line between the filter and the tank feed
I trimmed the ends of the rubber pipes I could see and remade the seals
I fitted a new return valve (the plastic thing on top of the fuel filter)
I fitted new O-rings on the fuel rail pressure regulator
All new clips around the filter (the correct type from the dealer) - the only one I haven't looked at is the tank end under the van.

I still see bubbles at the clear pipe where it enters the low pressure pump.
There is a vacuum build up in the fuel tank, driving with fuel cap loose doesn't seem to make a difference. Is there a valve to let air into the tank? Is it possible to get at without dropping the tank?

It's really getting annoying now.

If anyone has any ideas what to do next I would be eternally grateful

 

[lindenengineering]

Yes replace the suction hose at the tank connection to chassis fuel line with a genuine MB part and DON'T cobble it up by adapting a length of fractional inch commercial fuel hose, if you have done so!

Rather use the factory hose having an 8 mm format molding one end & 10 mm at the other.
Every van that comes in the shop with fuel aeration issues gets a new one.

Try that first.
Dennis

 

[Crosscut]

Yes replace the suction hose at the tank connection to chassis fuel line with a genuine MB part and DON'T cobble it up by adapting a length of fractional inch commercial fuel hose, if you have done so!

Rather use the factory hose having an 8 mm format molding one end & 10 mm at the other.
Every van that comes in the shop with fuel aeration issues gets a new one.

Try that first.
Dennis

Brilliant, thanks, is that the same scenario at the filter end?
It seems like a standard piece of fuel hose doesn't work very well there but at the dealers they said they don't stock that part and just to buy regular fuel hose. The piece I removed was all chewed up inside from the fuel filter union.

 

[hkpierce]

Presuming you have indeed no/eliminated air leaks at the points you have identified - I am not familiar with the OM611 fuel filter. But on the OM612 there are 4 other points to look at: 1) the bleed valve on the top of the filter; 2) the water drain valve (2 points of leakage - the base of the valve and the needle valve); 3) the WIF sensor because either the O-ring is not sealing or the sensor has not been properly seated with the required 90-degree turn; 4) a cracked fuel recycle valve that is located on the top of the filter.

 

[lindenengineering]

The hoses you need are suction A9014761826.
The return hose (less important) 9014761526.

For info the parts list drawing is total crap so no parts man wants to try to decipher a silly line sketch, more akin to a 3 year old kids scribble on notepad.
All the best
Dennis