Fuel guage problems

[MadDog]

Hi allI,m having a bit of an issue with my fuel guage (in dash LCD bubbles) it doesent read correctly, sometimes its ok and then other times as i,m driving it falls to zero, I,m wondering if it is an electronic fault or the float switch in the tank and wondered if anyone else has had this problem.Any help greatly appreciated

[BJ]

Just before my first "B" service a couple of months ago on my 450 my car started showing odd reading for fuel level. Mercedes drained the fuel tank, confirmed that it was reading wrong... something about a fuel level sensor. They replaced a couple parts under warranty but it still often shows one bubble less than full after it's full and then a bit later reads full again. BARB

[Coast Steve]

I get the same thing from time to time, mostly when the tank get's low or it's filled to high.MB made a problem fuel gauge in the tank I would say

[ARTZ]

I thought that once a blob disappeared it would not return until the car was shut off and more fuel was added (or park on an incline). I know that when I get below 5 litres and starts to flash if I head one of the hills in Fredericton (which is built on a fairly steep grade) I can get my gauge to show 5.5 or even 6.0 litres remaining.

[Speedie]

The gauge sensor part is just a winding of wire with a metal slider - if any grunge builds up it changes the resistance of the circuit (basically the sensor acts like a variable resistor). I had the issue just before I started my trek a few daygs ago - couple tanks with diesel conditioner in them and the gauge is back to reading full when full and accurate when empty. It is a common issue - not just with the smart - in fact Shell had a big lawsuit about it with their fuel gumming up gas powered vehicles a few years ago.You will find that going on inclines can trigger the 5l count down prematurely - when the tank is empty the float can move in a much wider range and momentum can come into play.Cheers,Cameron

[garthD]

I had a problem with the gauge misreading that began last year just as winter was starting. Merecedes said that replacing the fuel pump might help...it didn't. Problem didn't fix itelf until after I'd had 2 or 3 tanks of summer fuel once the tempertaures warmed up. I think the cold temperatures and winter fuel just "gummed" things up for me...garth

[MadDog]

Hi All, thanks for all the replys it never occured to me that it might be the fuel gumming up the guage (Diesel is an oil after all) I will try the diesel conditioner that Cameron suggested and hopefully that will help, thanks again

[ARTZ]

Always buy your diesel from a place that gets lots of business; this way they are always getting fresh diesel and you know it hasn't sat around for a while.Why would diesel gum up now? It is still summer; at least in the Atlantic.

[MikeT]

The fuel gauge in my green car has been behaving very strangely for the past couple of weeks. Filling the car will often bring about the usual 4 or 5 blobs, then the next time I start it the gauge reads two or three blobs, than up to 5 again. It does this throughout the range, often reading 0.0 L when the tank has 7 L in it.I have started treating it with Howes Meaner Power Cleaner and I hope it "smart"ens up!

[Alex]

I have had these problems too, often reading one or two blobs low after a fill, sometimes it does go to full after a while, sometimes not. Once I had it drop to 0.0 liters right after a fill, it slowly came up to 4 blobs after 100 Km. Mostly on Chevron fuel.Since switching to Husky/Mohawk it has been PERFECT!!! Also a touch better economy. I'm sold after 10 tanks and no more trouble.

[bilgladstone]

Thought I had a picture of the fuel sender someplace............

Here it is!

B

[MikeT]

Ewww, an SU carb!

[Leadwing]

Ewww, an SU carb!

(Slightly off-topic...my apologies) I remember those from my "real" mini days and my morris minor convertibles. They actually worked ok for me, though others I knew had problems with them.

[Speedie]

Meanwhile back at the farm.....There is also another fix the Mercedes can do - when they reflash the computer in the car it also recalibrates the fuel gauge (guess they can creep) - I was having a problem with my guage never reading full (which is a lot better than reading full when it is empty!) - when they did the EGR they reflashed and the problem vanished - some fuel treatment won't hurt either. Caveat though to those we remaps - it also clears that too.So if you are still under warranty - complain about the EGR valve (if you don't have the latest) and you will get the gas gauge issue helped out as well. Cheers,Cameronp.s. SU carbs are real fun if there is more than one! I think I learned a few cuss words from my Dad while he tried to balance them.

[MikeT]

I drove the green car up to Parksville in the thick smoke yesterday and the gauge was reading correctly for the entire trip. The Howe's seems to have worked so far. Today the white car was getting A/C surgery at TPM. And we are in Seattle....

[MikeT]

Got the white Canada 1 back with a new l.p. fuel pump/sending unit, RE & RE is the solution for this problem for cars under warranty. Value of repair about $500.The green car's sending unit will be treated to a new fuel additive at TPM and by reports it should clean up after a while.

[bilgladstone]

Got the white Canada 1 back with a new l.p. fuel pump/sending unit, RE & RE is the solution for this problem for cars under warranty. Value of repair about $500.The green car's sending unit will be treated to a new fuel additive at TPM and by reports it should clean up after a while.

I thought MB absolutely forbade fuel additives?

[MikeT]

That's what the manual says. I know how you always are by the book.

[bilgladstone]

That's what the manual says. I know how you always are by the book.

There's a book?

[Francesco]

Maybe that's a 2006 problem? My LP pump broke within the first few thousand Km, too (my first warranty repair back in July 2007).

[MikeT]

The pump was fine, just the sending unit was erratic.

[Francesco]

Ah. No, mine was making clunking noises whenever I stepped on the pedal. I have a question for you in the smart-gebrauchtteile thread.