Fuel tank empty 1 side? W212

[Coolguy18]

Hi guys, hope you are all well?

I am after a little bit of information on how these saddle tanks work on these Mercedes w212.

short story but our e class diesel keeps braking down due to fuel starvation, the engine will die and the right hand side of the tank with the pump is bone dry and the passanger is full.

The pump is working fine, the suction part is working as it will move fuel from the right to the left BUT there is no flow coming back to the right hand side of the tank?

from what i understand is, the right hand side with pump will feed the engine with fuel and fees the left side with fuel. And I can't figure out how does the fuel get back from the left side to the right??

Pump is good
Both leVel sensor are ok

Any information would be a huge help, mainly on how the system works?

Regards

 

[star]

Have you had any work done recently on the injectors or needed to remove the injectors?

 

[Coolguy18]

Have you had any work done recently on the injectors or needed to remove the injectors?

Hi, thank you for the response.

Nope no work has been done at all.

Basically the car was driving fine and the fuel gauge was half way and the car broke down.

I plugged the car in and noticed the fuel pressure was at 0 bar upon cranking and the black fuel filter in the engine bay was dry.

I lifted the rear seat up and I removed the caps off the fuel tank and that's when I noticed the left side of the tank (passanger side with level float unit only) was full of fuel and the right side of the tank ( driver side with level and pump) was bone dry.

I placed some diesel into the right hand side of the tank and the car fired up perfect but I noticed while its running and the pump is supplying the fuel filter and rail with fuel perfect, and it is also pumping fuel from the right hand side of the tank into the left, but nothing frim the left side of the tank is coming back over to the right hand side, so the car will die again as it will run out of fuel due to pumping it in to the left side of the tank etc.

 

[Coolguy18]

So I am a little confused on if the pump is pumping it over yo the left, what controls the fuel going back into the right hand side of the tank?

 

[mersum1es]

Venturi system... very common fault in W203, has been not a big issue in CR3 and up systems... but not saying it wont happen.

 

[Coolguy18]

Venturi system... very common fault in W203, has been not a big issue in CR3 and up systems... but not saying it wont happen.

I think the venturi system is working as its pumping fuel from the right side to the left?

 

[Coolguy18]

And also I don't think you can mix up the pipes either so the fact whe. The pump in the tank is running it is also filling up the left side of the tank, so I would say it's working fine.

I just don't understand how the fuel is ment to get back from the left side to the right if the venturi is a one way system (pull fuel from right side of tank to the left)

 

[Coolguy18]

Any one please?















Still having issues where the

 

[star]

Ok I have seen the leak off pipe have a caught seal, not leaking but an air leak not allowing the tank to balance.

 

[Coolguy18]

Ok I have seen the leak off pipe have a caught seal, not leaking but an air leak not allowing the tank to balance.

Ok thank you I can check that.

Can you explain what pipe feeds the fuel back into the right hand side of the tank?

 

[andrew056]

We had the same issue with our petrol CLK , the local Indie sorted it in the end after some head scratching but did involve new pump and about £300. I'm still not clear how it works .

 

[mersum1es]

http://mbworld.org/forums/attachments/c32-amg-c55-amg-w203/212562d1308458116-fuel-pump-bad-c32-screenhunter_10-jun.-18-21.30.jpg

 

[Coolguy18]

Hi guys, thank you fot the response.

It's got a new bosch low pressure pump in the tank just for reference.

I did pull the pump out the tank and sender out of the left side so I could understand it a bit better.

So as I can see:

Right side sucks fuel up

Fuel goes over to left side of tank via a tube and straight out the top (green fuel line) which feeds the fuel filter/rail.

This side of it I think is ok...

Now the return fuel that comes from the engine goes in to the left part of the tank (black fuel line) though the left fuel sender and looks to ho though the suction jet which should feed the right side of the tank etc

I think that's correct....

I did smoke test all fuel lines and and they are fine no leaks.

If I am struggling to get fuel returning is there a valve or solniod that controls this?

 

[Coolguy18]

We had the same issue with our petrol CLK , the local Indie sorted it in the end after some head scratching but did involve new pump and about £300. I'm still not clear how it works .

A new high pressure or low pressure pump?

 

[mattkh]

I did smoke test all fuel lines and and they are fine no leaks.

Just read the thread again. It is a diesel, which does not like air in the pipes.
How many seals in the fuel lines have you replaced...?

 

[Coolguy18]

Just read the thread again. It is a diesel, which does not like air in the pipes.
How many seals in the fuel lines have you replaced...?

None have been replaced.

I have smoke tested the leakoff side and no air leaks, I have also smoke tested the return pipe from pump to tank and no leaks

 

[mattkh]

None have been replaced.

I have smoke tested the leakoff side and no air leaks, I have also smoke tested the return pipe from pump to tank and no leaks

One more wild guess..
Is there a air vent from the top of the tank to say the filler pipe.? If so, is it blocked..?

 

[Snake Charmer]

Interesting setup, I would like to see how the suction pumps are built. From what you describe and the link @mersum1es posted, I would be looking at No3 "Pressure Regulator Valve" and No2 "Bleed Valve" to see if they are working correctly and allowing No1 "Left Suction Spray Pump" to function as that looks to be siphoning fuel to the fuel pump in the splash bowl.

 

[andrew056]

A new high pressure or low pressure pump?

I think there may be two pumps in the tank I know they got the wrong one to start with but the second try fixed it , I would imagine that they are both low pressure. Somebody must know how this is supposed to work.

 

[Fastevo1]

None have been replaced.

I have smoke tested the leakoff side and no air leaks, I have also smoke tested the return pipe from pump to tank and no leaks

Out of interest did you sort this as I have a similar problem with a R class.