Does anyone know the ohm range for the fuel sending unit that's attached to the fuel pump on the left side? I've searched and searched and cannot find a definitive answer.

In short, I replaced the pump and my gauge is fixed at half full, or half empty... After replacing the replacement, I had the same issue. Using a multimeter, it shows 20 ohms while empty and an exceptionally high range for full. This was tested on yet another pump of the same brand from a green big box store with the same results.

With a completely full tank, the on board diagnostics show the left tank 0.00 and right tank around 24 liters. When I leave it connected, I can pull the pump out of the tank and add the float drops, the gas gauge starts to rise.

Unless anyone can think of anything, or has the ohm range lying around, I think my only option left is to go buy another variety of pump from elsewhere. Thanks

 

Start by using a multimeter to check for an open in the left sending unit wire.

 

I did that, all checked out well. It was after that, when in frustration,I pulled the entire pump out and decided to throw the key in and saw the gauge changing its reading. As the float went down, the gauge read higher. As I lowered it back into the tank, the reading dropped.

 

Please provide car information - year and model.

Did you replace both the fuel pump and sending unit on the left side?

Do you have the Bentley factory manual and did you follow the instructions? Is it possible that the installation was done incorrectly?

 

She's a 2010 S, R57. No manual, and only replaced the pump. The right side has been pulled, but only to ensure the float was moving correctly and to change the filter. On board shows right side reporting correct values. I'm not certain how the install could have been flubbed. It's all pretty straight forward, especially after having torn the engine down to replace bent exhaust valves after the chain guides gave up.

 

If you're confident about the installation, your focus should be (1) the left sending unit and (2) excess resistance in the left sending unit wire or connector pins. The latter could be assessed with voltage drop tests.

 

Update:

All is well and back to normal. For anyone who might, and likely will, run into this same issue, the problem is the fuel sending unit, or rheostat, attached to the pump. The "hidden menu," option 6 is your friend here. On empty, each sender from both tanks should read 300 ohms, or thereabout. When full, they should read 20 ohms, or thereabout.

I went through three Direct Import brand pumps, all with the same issue. I've read, and can't say with any certainty, Direct Import is made by Delphi. Take that for what it is. I went with the slightly cheaper option, US Motor Works I think it was, and bench tested the sending unit to ensure it was reading as it should. After install, I got back into the menu and went to fill up, watching both senders reading correctly, and the tank indicator reading same.

Hopefully this will help someone as I spent more time digging than I should have. Also, simply switching the fuel sending wires WILL NOT cause it to read backwards, or correctly. Happy motoring and thanks to all who replied!