henri2497

Hi, I have a 2002 c240 automatic. Situated in South Africa.

Now here is the problem and any advice would be appreciated.

My vehicle acts like it is out of fuel with the fuel gauge displaying 1/2. Now I am quite sure at least half a tank of fuel is still inside. After reading various forums it has become apparent that fuel is not transferring from the left side to the right. The right side fuel pump was replaced in 2018 and the fuel filter in 2020. Now, to get to the point, in my opinion the sender unit must have gone bad, but after reading more about the issue it was mentioned that there is various things that can cause this problem.

If anybody has any advice and or anything I can check before replacing the sender unit it would be of great help as this will have to happend on a budget and I don't want to fix the wrong thing.

Thank you in advance.

Russell Ormerod

Simple. Check fuel delivery ! If pump cannot deliver no transfer will take place

henri2497

Thank you for responding. I am however not sure what you mean. How do I check the fuel delivery ? Excuse me, I am quite the novice.

Russell Ormerod

Remove the rear seat. Remove the cover to access the level sensor. ( PASSENGER SIDE) There you will find a 8mm hose. Remove the hose and place into a bottle. Start the car and?, you should get about 1 litre in 30 seconds

henri2497

Okay and if this is not the outcome, do I replace the fuel pump or sender unit on the left ?

And if this is the case, what else can be the problem ?

Russell Ormerod

There is only one pump and that's on the right side. If delivery is poor it needs to be replaced

henri2497

So the fuel pump is the only part supplying pressure and not the sender unit ?

Russell Ormerod

Correct! 1 x fuel pump for delivery of fuel and 2x sender units to measure the fuel level. System is designed to always keep the right half full. So when your gauge reads half tank the right half should be virtually full and the left almost empty.

henri2497

For starts in the moring, the car usually needs two cranks to start. From what I read this also indicates a failing fuel pump. My question to you is though, can a pump fail partially or is it instant and then it is dead ? My theory about a bad sender unit has bassicly passed now, and I am set on the fuel pump.

Russell Ormerod

Yes I can fail partially. That's why you check delivery! A pump that delivers 300ml in 30sec will still allow the car to start and run. But at high load the engine will starve of fuel and the tank will run dry at half level

David275

I had this similar issues few months ago, where the fuel run dry at the pump side which is the right hand side of the rear seat, the other tank at the sender unit will still have much fuel, I changed the fuel pump and not the sender unit and that solve the whole problem.

David275

I had this similar issues few months ago, where the fuel run dry at the pump side which is the right hand side of the rear seat, the other tank at the sender unit will still have much fuel, I changed the fuel pump and not the sender unit and that solve the whole problem

Russell Ormerod

Correct.. thats the reason why you check delivery always and not pressure.. if fuel volume is low it will not transfer. And you will end up with no fuel at the pump and the rest of the fuel in the left half of the tank