Fuel gauge problem Mercedes C 200 classic 1997

[redoctopus1]

After filling the tank the gauge shows zero and low fuel light comes on intermittently but after using some fuel (About 45mins) it goes up to show almost full and works ok until the next refill.
Can anyone figure out how to fix it please?

 

[Mickymoody]

Gauge regulator fault? Located behind the dash?

Or a sticking float in the tank?

Or a venting fault on the tank? Requires a new fuel cap? When you have used a full tank of fuel, does the petrol tank 'hiss' when you remove it? Is it petrol or diesel?

Cheapest and easiest is replacing the fuel cap, then maybe the float in the tank. But a Merc being a Merc, could always be a fault on the dash electronics. As always check out the official owners club.

 

[redoctopus1]

Thankyou for that advise and I will get into some testing ASAP

 

[redoctopus1]

The Merc C200 1997 is petrol and no the fuel cap does not hiss on removel.

I thought that I might try to refuel it with the key turned to show dials working but motor off and watch what happens as the fuel goes into the tank.
It may then show at which stage the fault occurs or it might even recalibrate it's self.

 

[Mickymoody]

The Merc C200 1997 is petrol and no the fuel cap does not hiss on removel.

I thought that I might try to refuel it with the key turned to show dials working but motor off and watch what happens as the fuel goes into the tank.
It may then show at which stage the fault occurs or it might even recalibrate it's self.

After filling half way and above, when you remove the filler cap, it should hiss, when you remove the filler, so in theory, the tank isn't getting pressurised, and hence the float isn't reading correctly. So the easiest, and cheapest option is to replace the filler cap? Does it open with the vehicles key? Maybe get a temporary filler cap, or one from a scrapyard to try?

After you have filled up, it then creates a vacuum, that the float can now read, but the filler cap is faulty, thus allowing fumes to vent, and thus causing the failure?

 

[sisize]

Im a mercedes technician, the usual (but not always) fault concerning c class fuel gauges is the actual tank senders themselves. the potientiometer on the the sender unit dosent transmit properly, causing the above faults. I would still try a new fuel cap first but usually its the senders to fail. The instrument clusters dont tend to produce the fault your experiencing.