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 e220 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

kajtek1

You have 2 pumps, where technology has some changes between MY.
Older models have Venturi pump, powered by return fuel who would pump fuel from "dead saddle" to the 1 with active pump.
I think newer technology has 2 electric pumps, but I have no experience with it.
Either way, that makes quite tricky job, where even professionals do lot of screw ups.
Seeing this is your 1st post, what is your experience?
Welcome to the forum

Coolguy18

Hi there, thank you for the reply.

this must be a venturi style as it has a large pump in the middle and a larger plastic outer plastic case with 2 pipes that go over to the other side of the tank, I take it as it has this style there is no transfer pump between the 2 sides?

So basically if i remove both caps off the fuel tank the fuel pump in the right hand of the tank will feed the engine but will also pump fuel into the left hand of the tank untill there is no fuel left in the pump side.

I will always end up with:

1. Engine cuts out.
2. Left side of tank full of fuel.
3. Right hand side bone dry.

All pipes are connected as they should inside the tank.

I am confused to why the pump is using vacuum to send fuel from the right side of the tank over to the left but no fuel is coming back to the right side of the tank which is causing the fuel starvation issue?

kajtek1

Did you search old topics? We do have forum member handle konigstiger, who has access to WIS and is great in helping with those.
If you don't find old topic with the file, PM him for help.
From what I know small misalignment makes 2nd pump not doing the job, so working blindfolded on them is not going to work.
The cars I know have main fuel pump on left side, when sounds like you might have different model.