1998 C280. The fuel gauge fluctuates between full, empty and 1/4 even when the gas tank is full. There could be a problem w/ the fuel sender. Does anyone know where the fuel sender is located or get access to it? I thought it's under the back seat, but after removing the back seat, i didn't see anything there.

 

There are two of them located in the lower front of the fuel tank (it has two parts). Unfortunately, these are a common problem item that need repair.

 

Do I need to remove the fuel tank to get access to these two sensors, or just simply jack up the car and do the repair without removing the tank? Should i replace one or two sensors? thanks.

 

Try a couple of bottles of Techron Concentrate,
I had a similar promblem, and now all is well.
Give it a shot.

 

I tried the Techron cleaners already, 2 bottles, 2 tanks. No improvement. And indy shop quotes $400k to fix the problem. No thanks. Since it's accurate at below 1/2 tank, I'm not going to fix it. Someone in one of the postings mentioned that the float in the fuel sender may need to be readjusted.

 

$400 doesn't sound bad as the sensors are over $100 each online, and the tank has to be dropped as I recall. As xvv said, it's a common problem. I think some people have had success with repairing only the wires to the sensors. My car went from vaguely accurate, to accurate when less than half a tank or so, to essentially no gauge, I just live with it for the time being.

 

Phil is right. For $400, it might be worth letting them do it due to the hassle factor.

 

It's a common problem for the C-Class. Unfortunately in my case, my gas always comes with techron and it didn't fix the problem.

 

Well, i just got a 1995 c280 with arratic fuel gauge, added a whole bottle of Seafoam to the full tank of 94 octane gas. It seems like after about 3-4 days the gauge calmed down, at least at the bottom half of the tank. Filled up the tank to full again, willl monitor to see if the top half will be OK.

So, I'd suggest to use Seafoam once in a while, it will clean the fuel system at least.

I've used this staff on my bikes to clean rough rinning and it works.

 

I have a similar problem with my '95 c280 except the sending units have been replaced(don't need to drop the tank) and I was told it's probably the internal leveling mechanism in the tank that balances the fuel between the saddle tanks. Before changing the sending units I lived with this problem for some time by just filling up after 150 miles orso and am inclined to do the same again. Any thoughts or advice will be much appreciated.

 

No need to remove the tank just jack up the car and remove the covers at the front of the tank and remove the sensors. Hopefully you haven't left much fuel in the tank.