Like clockwork, my C43 has decided to pop another electrical failure right before service time......my fuel gauge has stopped working correctly. It's basically an intermittant erroneous reading of empty (or close to empty if light isn't illuminated) that seems to generally be happening on hot starts. Perhaps of note, or more likely by coincidence, this was first noted after my most recent trip to the gas station. Not knowing really anything about the w202 fuel system, does anyone have any idea what might be going on? Fuel float failure, CAN failure, ???? Thanks in advance....I'd like to try and take care of this myself so I don't have another $800 bill (for the windshield wiper motor last time).

 

Anyone? bumpity bump

 

How's your battery?

 

No way to be sure without checking it electrically, but the most common point of failure is the fuel gauge sender in the tank. When in doubt, go with the moving part.

 

Battery is 100%, or at least I don't have any reason to believe otherwise (easy cranking on cold start, no alternator warning light, etc). I figured it probably is the sender....is that a DIY kind of thing, or does it necessitate disassembling the fuel tank? I'd probably be up for that even, but most of my tools are 3000 miles away in storage unfortunately...

 

I think there are two senders at the bottom of the tank. I also think you need special tools to get them out and I recall there can be complications. Something to do with the fuel pump and something else to do with new senders possibly requiring version coding with the dealer's Star computer.

http://www.detali.ru/cat/oem_mb2.asp...SGR=015&SGN=01

All told, probably a good one to leave to a pro.

 

Yeah, like I said it is due for a service so at least it's not inconvenient. Definitely seems to be a hot start thing.....anyone know if the sender unit a resistor type unit, or a float?

 

The WIS says the first thing to check is that the sender isn't hung up on the fuel line and the lines aren't kinked. Per the C43 secton of the WIS, the R&R procedure is as follows:




You did see the part about "no smoking", right?

Post back whether this helps, if the line was kinked, hung up, and how you fixed it. THanks

 

Very common for these fuel senders to fail. The new senders (genuine at least) have gold contacts to prevent premature wear/corrsion. The contacts in the tank can be cleaned but since they are a little more labor intensive than other models to remove from the vehilce then it makes more sense to replace them.

I just had to do it to my car last weekend........not happy!

Probably best left to a workshop to do because it's hard without a hoist.

 

Same problem with my '99...fill the tank and the gauge read empty and the fuel light would remain illuminated. After 50-60 miles the gauge would then move to "full" but would remain "full" for 150 miles or so, then begin to drop rather quickly to 1/2. Really whacky! I read some posts here and was skeptical, but gave it a try and, in fact, the use of fuel injection cleaner does appear to solve the problem entirely! With this last tank, I drove until the fuel warning light went on, added 2 gallons and the light went off and reads just under 1/4 tank, then filled it completely and the gauge reads full!! YEA!!!

 

Any idea what the bill is for this kind of repair out of curiousity? Thanks for the help guys BTW!

 

Maybe I'll try that. On "normal" mode, it seems to be decreasing at a normal rate for the mileage I have covered since the last filling, but I will keep an eye on it. I remembered to set the trip odometer when the gauge failed for the first time (immediately after the filling) so it should give me a pretty accurate guesstimate of when it will need gas. Maybe I just got a ****ty tank of gas???

 

The WIS mentions the gauge issue specifies replacement of the sending units with new ones that have gold contacts; $600-800... Apparently the oxygenates used in gasoline corrode the wiper contacts...

 

yay....thats basically the average then. Not to sound cheap, but I'm not sure why MB can't make a car that doesn't charge you 800-1000 bones every 10 months for random electrical gremlins. And on top of this, I have a phantom A/C sensor failure....like it refuses to turn on the cold A/C air on occaison, and after shutdown and re-start its all good. Man I need to sell this piece of ****

 

Awww..is the honeymoon is the honey moon over?

 

For the AC, have you gone through the diagnostics via the HVAC controller? Many times it's an inexpensive sensor. IHTH

 

Yeah, I'm pretty sure that what it is doing is just not sensing that the A/C needs to come on.....because the system is 100% otherwise, and has been serviced 3 times in the last 2 years.

 

haha...the honeymoon was over 2 years ago, but this just drives the stake a little further in. It's too bad they couldn't do as well with the "accessories" as they did w/ the drivetrain and body.

 

Fly,

My C43 currently is in need of an evaporator, so dont feel bad about your AC issue. i had the EXACT same symptoms when my '97 C280 AC started acting up. Took her to the stealership and 1 evap temp sensor later i was back in comfort. 170 bucks but they didnt charge me for labor, so i guess in this case theyre just a regular dealership, no stealing that time, at least on the labor

 

Does this work on the 95s? Probably not since we have a different A/C head unit.

 

You'll have to try it. Hold in the REST button and see if the codes are available. I know my W208 has fewer codes available than the W209. I'm guessing the earlier the year, the fewer the codes.

 

Cool, good info guys....I'm glad to at least hear I'm not the only one

 

im tellin you, evap temp sensor. the AC would be running good and then all of a sudden the air would turn humid and not cold, this symptom will come and go intermitently until the sensor decides to go bad all the way... just replace it, its pretty cheap

 

haha....I wasn't doubting you man, thanks for the help!

 

Another satisfied customer I see...

I had my fuel sending unit go out twice while under warranty...