jeff ingrum

have alreay replaced drivers side sending unit and still same problems returns, when i fill tank fuel gauge will work ok but hangs up at half way line until fuel is exhausted,in other words half to empty gauge has no reading at all until out of gas,
so is this a common problem with this car

tjts1

Your passenger side fuel level sender is boned.

slagdemon

From reading here, the passenger side is the fuel pump The drivers side is the fuel level sender. Is this not correct?

tjts1

This this is not correct. There are fuel level senders on both sides of the tank

slagdemon

How can you tell which is bad if your gauge is reading incorrectly?

tjts1

You need an MB scan tool that can read live data from the rear signal aqusition module. That'll show you fuel level signals on both the left and right side.

slagdemon

Guess I should have asked how the home mechanic can tell which is bad. I don't have a MB scan gauge. Should be a resistance value or something I can go by though, right?

tjts1

This is for the 211/219 but the saddle tank setup on the 203 is the same as this.
https://www.ms-motorservice.com/en/t...-tank-modules/
Each side of the tank has its own float and sensor. The fuel return is used to siphon fuel from the driver's side to the passenger side so the pump is never starved of fuel.
sorry I don't know the pin outs or resistance values to look for.

slagdemon

Good info, thanks tjts1. I'm probably going to pull both sides and look for anything "weird". I'm hoping maybe there are some contacts that can be cleaned or something otherwise. Either way, I'll video it and throw it up on youtube.

C230 Sport Coup

There is the possibility that someone replaced the pump, and failed to connect everything correctly, perhaps?
Autozone has a pump tool to loan as well as pressure tester.

slagdemon

I pressure tested my pump and it was right at 55-57 psi. The only issue is the level. I don't think its correct. My tank showed 1/4 left when the guy sold it to me. I put a couple gallons in and it fired up after I primed the pump. Seems its reporting incorrectly or a pickup tube on the pump became disconnected or something.