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benzdude
08-19-2003, 11:28 AM
My fuel gauge doesnt work. actually it only worked when my tank was full and anything past 3/4 tank would register at 0.

now it only works now and again.

Someone suggested that it might be the fuel sensor/s. ( I believe there are two of them)

question: does anyone have any experience or knowledge about the fuel sensor/s location and/or removal? I supposed they are located above the fuel tank?

thanks

Luwin1026
08-19-2003, 11:40 AM
Not sure if they are actual sensors, but rather the fuel sending units.

kameraguy
08-19-2003, 02:41 PM
This is a problem that plagues a few of us as well. I also have the same problem, and yes, there appears to be two sensors that could be at fault.

If you check for trouble codes, you might see a fault generated to confirm that is your issue.

However I don't think it tells you which one has failed. When i saw the code it wasn't specific.

When i asked about fixing it, I was quoted around $700....$700!!!

Apparently this fix requires a lot of effort, which = $$$ Labour.

So i don't know if anyone has actually fixed this issue before?

CKlasse
08-19-2003, 06:38 PM
Fuel baffle maybe? It happened to my previous VW, I am not quite sure about Merc. It does take quiet a work to pull down the fuel tank, and replace the sending unit.

On my old VW the baffle simply stuck on the bottom instead of staying floating on the gas.

rad2000
08-20-2003, 11:12 AM
I had the gas guage problem with my 1995 C280. It was a faulty sensor. The dealer replaced it for free somewhat after the end of warranty. Apparently they were aware that this had been a problem. Not sure how old/how many miles are on yours, but it might be worth a try.

96W202
01-20-2004, 11:20 PM
I have the same problem, the fuel gauge jumps up and down after 3/4 tank. If the fix isn't a DIY and it really does cost $700, would it be wise to just leave it as is and just keep check on the level of gas?

How'd you get the dealer to do it for free Rad2000? Doesn't sound like something the dealerships would do for us without charging an arm and a leg.

sph17
01-21-2004, 05:54 PM
Driving home after a full tank of gas, gauge dropped like I had sprung a leak. My car is StarMarked, so dealer replaced Fuel Sending unit. No sure if they only did one or both, but problem has not re-occured.

kameraguy
01-21-2004, 06:08 PM
I read on mercedesshop, this condition is more prone to occur if the gas tank is too full. Many people who "top off" report this issue.

In my case, I don't top off per-se, but I let the fueling stop on it's own. But maybe when the trigger clicks to the off-position, the tank is technically too full?

I do notice it happens less if I don't fill up completely.....

Either way, it's a straight-up retarded problem.

I checked my codes and i get a P0140 open fuel system code ( I believe that's the TC # from memory....).

But I haven't had any issues because of it.

I just religiously fill up my tank and reset the odo. I get approx 280-305 miles to a tank with my C36. I just refuel around 260miles and ignore the gas guage.

Stupid gas guage....:rolleyes:

moebiusgold
01-21-2004, 08:37 PM
Kameraguy, if that's the code you are getting you have problems. I am confused because this has nothing to do with gas level and if this is read threw the OBD port, you can't get at any of the chasis or SRS or ESP or ABS or BAS error codes.
P0140
DTC Definition: O2 Sensor CKT No Activity (Bank 1 Sensor 2). My definition: Check your rear O2 sensor. I have a used but looks Brand new Spare, for a '95. They are more expensive than the front ones. This makes the computer unable to monitor Cat heating and efficiency. I bet it only affects WOT but I'm just guessing. Does engine load read 100%. Did you own it when this wasn't this way?

BTW I don't think it is ever a good idea to ignore P0 codes unless you know exactly what the consequences are.

From:OBD II codes (http://www.actron.com/code_lookup/index.php)

mis-u-jerr
01-24-2004, 08:09 PM
I've had the fuel sending unit replaced twice under warranty. The gauge doesn't drop after fill up, what mine does it that when you turn the ignition on, it will just stay at empty and does not move. My service adviser said that the MTBE in the gas kills the unit and that they get a ton of car in during the winter months...

jlomon
01-25-2004, 08:01 AM
I get this problem with my 94 C280 as well, but it only happens on a full tank, and in the summer when it is particularly warm. If I fill the tank, the fuel gauge will drop dramatically after a few miles of use, down to about the 3/4 mark. Then it will rise up to full again. When I shut the car off and restart it, the needle once again points to full. The gauge seesaws like that until I have about 3/4 of a tank left, then it stabilized. My solution? I live with it, and use the trip odometer to keep an idea of how much gas is in the tank. But the "overfill" suggestion that someone else made seems like it fits this scenario. If the gas you pump in to the tank is cooler when it is in the holding tank at the gas station, about 15 degrees C I think. When you pump it in to your tank, and its hot out, it should expand a little bit, creating the "overfill" scenario that is messing with the sending unit. If it was a cheap fix, I'd get it done. But $700? No thanks.

Jonathan

Eurosport
01-25-2004, 08:41 AM
i had the same problem couple of times
both times it happened i overfilled the tank
after taking some hard corners it came back to normal
hasn't happened since
(btw mine dropped the needle all the way down to empty just after refill, then it would bounce back to full depending on bumps in the road etc., just remember don't overfill specially on hot summer days).

SLAMMED_C
01-25-2004, 02:06 PM
In regards to the fuel sending unit issue.. its not a DIY job.. the fuel tank needs to be drained and then the fuel sending units need to be replaces.. they are located on the underside of our W202s on the bottom of the gas tank... need to get the car in the air.. remove covers for sending units, need special tool to remove sending units also! there r 2 sending units.. one on the left I think gets the return fuel from the engine and pushes it back into the tank to be reused again.. the one on the right side is the fuel level sensor/fuel tank pressure sensor.
and from what I know the topping off issue doesnt cause erratic fuel gauges.. but can casue no start problems due to large amounts of gas getting into ur purge system soaking ur charcoal canister.

rad2000
01-28-2004, 07:32 AM
In response to earlier post, I took my 95 C280 to the dealer about 6 months after the warranty ran out, and they took care of it. I guess it pays to be nice to your service tech. A Christmas present in your last year of warranty might go a long way (no, I didn't actually do that, but not a bad idea). Lately (108,000mi), I've had the problem crop up again, always after a filling up too much. If I quit after the first pump shutoff, I usually don't have the problem. Nonetheless, it is annoying that a Mercedes should suffer from this kind of engineering problem.

kameraguy
01-28-2004, 07:49 AM
Originally posted by moebiusgold
Kameraguy, if that's the code you are getting you have problems. I am confused because this has nothing to do with gas level and if this is read threw the OBD port, you can't get at any of the chasis or SRS or ESP or ABS or BAS error codes.
P0140
DTC Definition: O2 Sensor CKT No Activity (Bank 1 Sensor 2). My definition: Check your rear O2 sensor. I have a used but looks Brand new Spare, for a '95. They are more expensive than the front ones. This makes the computer unable to monitor Cat heating and efficiency. I bet it only affects WOT but I'm just guessing. Does engine load read 100%. Did you own it when this wasn't this way?

BTW I don't think it is ever a good idea to ignore P0 codes unless you know exactly what the consequences are.

From:OBD II codes (http://www.actron.com/code_lookup/index.php)

Thanks for the info moebiusgold. I believe this was always present, and to be honest I didn't even know it was there until I bought my PDA scanner. When I took the car to two dealerships for unrelated issues, I did ask them about this code. They actually said it's probbaly due to the fuel sending units responsible for the gas guage issue. So I though eh, I don't want to fix it now.

But if this is more serious or unrelated, i'm going to go postal on Smythe and Beshoff.

Is the rear 02 sensor supposed to connect to the intake pipe that has 3.6 on it? I know there are two locations for this, but there is only one sensor on my car...right after the airbox. The other one after it towards the end of the pipe has a plug. Could this be missing?

I also asked the dealership about this and they said it's "normal".

pnsji
01-28-2004, 08:08 AM
Originally posted by kameraguy
Is the rear 02 sensor supposed to connect to the intake pipe that has 3.6 on it? I know there are two locations for this, but there is only one sensor on my car...right after the airbox. The other one after it towards the end of the pipe has a plug. Could this be missing?

In '97 C36, the O2 sensor is right before catalytic converter. The one right before the 3.6 is mass airflow sensor.

If you are missing an 02 sensor, your CEL will go on.

kameraguy
01-28-2004, 08:15 AM
susanto,

how many sensors do you have connected to your 3.6 crossover pipe? One or two?

Mine only has one....the one you mentioned. But there is another connection towards the rear of the pipe...but this one isn't connected. it has a plug.

Am I missing this or is it supposed to be like that?

pnsji
01-28-2004, 08:43 AM
Honestly I am not sure what you are talking about. I will check later tonight. In the crossover pipe, I don't think I have any sensor (If I remember correctly). If you can take a picture of what you are talking about, then I might be able to understand.

Eurosport
01-29-2004, 12:32 AM
i know my car has 2 Ox sensors
one before the cat one after the cat

but since you guys have 97's you could have 1

and that might explain the mysterious 268hp vs 276hp? less restrictive flow or just a more agressive mapped ecu


anyway
i do know there's a plug on the 3.6 tube towards the right side, the one that kam's talking about it has a wire pluged into it, i think it goes down towards the first 02 sensor been while since i been down there though