Fuel Gauge Shows Empty When Tank Is Full

[PamMcN 0]

About a week ago I filled up my Diesel Smart, and when I turned the ignition the fuel indicator showed about half full, then dropped to empty. I panicked and pulled back into the station only to pump another $11.00 worth of diesel. The pump had shut off after I filled up the first time. I got back into the car and the gauge showed a 3/4 full tank.

The tank stayed at 3/4 full, even though I knew I was going through fuel, and yesterday it dropped to 1/4 full. Today the fuel indicator showed empty and I pumped $12.00 worth of fuel before the pump shut off. The indicator is now sitting on empty although it's now showing 4.5 L.

Is this something my mechanic can fix or is this a trip to Mercedes?

Thanks,

Pam

[MikeT 744]

Don't waste your time and money at a dealer!

The fuel float is gummed up with waxy diesel sludge.

Buy some diesel fuel treatment like Petrolabs diesel additive and pour quite a lot of it into the tank at each fill, like 5-10 mL. After 5-10 tanks, it should clear up. If you add more additive at each fill, it should clear up sooner.

[tolsen 630]

Diesel bug slime perhaps. Complain to your filling station and get them to pay for sorting it all out.

Edited July 13, 2015 by tolsen

[smartnhappy 218]

Ya, what Mike said.

"Buy some diesel fuel treatment like Petrolabs diesel additive...."

I had the same trouble with a Smart with very low mileage.

Used Petrolabs for 2 or 3 tanks, and the problem disappeared.

Been using it since with great results.

[Alex 21]

Fuel brand matters. For my car, Husky makes my fuel gauge work well, Chevron and PetroCanada make it not fill up the last and sometimes second to last blobs. Fuel additives may help.

Disagree with the "waxy diesel sludge" bit though, I know my worst/strangest ever fuel gauge behavior was in hot summer filling up after 90 minutes highway drive then straight back on the highway. Diesel would be hot, thin and really good at dissolving wax under those conditions. It showed 2 blobs, dropped to one, dropped to none and a countdown at 0 liters, then gradually up to 8 liters, then all blobs came back at once. Something happens, but there would be a clear relationship between temperature, length of drive (fuel temperature and mixing) and gauge misbehavior if it was as simple as waxy deposits.

[TO Ed 9]

Find another place to buy fuel. I've had this problem a few times during the past 10 plus years. Had it again last month. Crap fuel appears to be the cause. My experience has been that it goes away with different fuel. Additives should help. I've always had this problem in the summer. Likely when refineries get rid of their crappy fuel.

[PamMcN 0]

Thanks so much for the reply. Can I ask where you got the Petrolabs? I called my local Canadian Tire with no luck.

Thanks,

Pam

[dmoonen 54]

The powerservice works good aswell use it in all my diesels, http://www.canadiantire.ca/en/pdp/power-service-diesel-kleen-cetane-boost-473-ml-0388048p.html

[Jerzy 8]

Thanks so much for the reply. Can I ask where you got the Petrolabs? I called my local Canadian Tire with no luck.

Thanks,

Pam

Hi Pam

I had same problem recently at Husky than filled up with Shell Power V and it came back to normal.

[tolsen 630]

Treat your fuel system with diesel bug biocide. Avoid slack tank, always keep your fuel tank pressed. Means less condensation and hence less water where fungi and bacteria can thrive.

[smart142 605]

Fuel brand matters.

My fuel gauge went ''wonky'' when I was in BC 3 years ago. It went back to normal in Alberta and has been good ever since.

[darren 192]

When I had my CDI, I only ever put premium diesel in it (Sunoco Gold, then Shell V-Power, and only VERY occasionally Husky or Pioneer premium diesel). I never had fuel gauge issues, and in fact had very few engine or turbo problems, either.

Buying quality fuel from a busy station really does make a huge difference.

Edited July 16, 2015 by darren

[Leadwing 565]

Pam, Just another thought...........

You may or may not know, diesel foams when it is being pumped into your tank. If you stop filling at the point where the foam causes the pump to stop, it is feasible to have much less than a full tank, depending on how much foam was created while pumping.

That said, yes, the brand seems to matter. I have never had fuel gauge issues, but I always use Husky except for the rare occasions when I am too far away from a Husky station and need a refill. The fuel gauge seems to be quite accurate in my particular car.

[SandyLane 1]

Ya, what Mike said.

"Buy some diesel fuel treatment like Petrolabs diesel additive...."

I had the same trouble with a Smart with very low mileage.

Used Petrolabs for 2 or 3 tanks, and the problem disappeared.

Been using it since with great results.

Ya, what Mike said.

"Buy some diesel fuel treatment like Petrolabs diesel additive...."

I had the same trouble with a Smart with very low mileage.

Used Petrolabs for 2 or 3 tanks, and the problem disappeared.

Been using it since with great results.

Sandy here. I had the same problem with my 2005 cabrio and Mercedes Midtown quoted me $3,000 to fix it, but recommended I just keep track of my mileage for refueling! Lame! I went to Active Green and Ross, Victoria Park, and they ordered a can of Petrolabs. Within an hour I was putting it in my tank. Within 24 hours, the fuel gauge started working again. It's been a few days now, the gauge is working perfectly and I've noticed the car's performance has improved. Thanks for the tip guys.

[Freedom95 1]

I had this problem for a long time with my 2006 Passion. I tried - really tried - additives but things just kept getting worse. I started going to a new independent Mercedes-trained mechanic and he insisted that I should only use Shell, Petro-Can or Esso diesel. Tried that, plus additives (including Petrolabs). No luck. Finally I took it in and he said I needed a new sensor, which is all part of the fuel pump. So I had him replace the whole shebang and I have had no problems since. (Still using "good" diesel and additives.) The only good news was that he sourced the pump directly from the manufacturer which was $150 less than getting the same thing from MB.

[tolsen 630]

That would have cost you an arm and a leg. A new fuel sender unit is cheap only £120 but labour is a real killer. Engine subframe must be dropped to lower tank sufficiently to remove sender unit. The job is more involved that one would think. A real pity there is no access hatch from inside the car like on some other makes.

I bet your sender unit was only fouled with diesel bug. A quick clean would have sorted it.

[dmoonen 54]

Bet that wasn't a cheap bill. Had to drop my tank to clean it out and it wasn't a fun task even with the proper tools and a lift.

[Freedom95 1]

Well, it may have been gummed up, but how do you know until you get in there? And once you have it apart (expensively), is it worth putting the old stuff back in and crossing your fingers? Cost about $700 but they changed oil and did a few other routine things as well. Mostly I posted this to say that sometimes it's possible that stuff just breaks. I was sure hoping the additives would kick in as they have for others here but it was not to be. The mechanic has been good. MB told me I needed new front brakes and I took it to him for a second opinion, and without even taking the wheels off he said I didn't need brakes. 10,000 km later, he still hasn't told me the brakes need doing. So I was comfortable with his diagnosis about the fuel pump. There were days when I tuned my SU carbs, and changed the clutch on an old Fiat in the rain on a gravel driveway by myself, but I'm getting past that now!