Ran Out Of Gas Twice - With A Half-tank Left?

[JIM HOPKINS]

I have a 1989 300E. Twice in the last couple of months, I've run out of gas. But, I had plenty of gas left in the tank. The first time, about 2 months ago, I had a quarter-tank. I've been careful not to run it past a half-tank until yesterday, when it went a little below 1/2...and, again, "ran out" of gas. Yesterday, it took 9 gallons to refill the 16-gallon tank. So, assuming the tank has not been crushed to half its size, which it hasn't, it is not recognizing or delivering any gas when it gets to 7 or so gallons left. I believe the fuel is pumped from the bottom of the tank. It runs fine otherwise, once it is filled again. No problems. Gas delivery is perfect. My friendly-neighborhood Mercedes repair pros don't recall coming across this exact problem. Have you????

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[oneill_1]

no...sorry, i havent run into this problem or heard of it at all....
just giving you some feedback so you wont think that we are ignoring you.

-OG

[DarkHand]

Fuel pump and fuel filter ok?

[shdoug]

If I had to guess, and I do, your pick-up tube is rusted half-way up.

[kiasu]

i have the same prob, my needle will show half tank and the warning light will be on, i have a 89 260E. Only on rare occasions will it show an accurate reading.

[rooney2006]

no idea, man.

[CharlestonN]

Yeah, i have the same problem with my car, the needle reads quarter/half tank but the reserve light is on, i usually rush to a gas station as soon as he light comes on, i have ran out of gas twice in this car because of this

Not sure what is causing it though, but i believe it is a fuel level indicating mechanism in the tank

[JIM HOPKINS]

When I refill the tank, COUNTING the gallon I pour in from the gas can, I can put in no more than 9 gallons. That means there were seven gallons in the tank when it "ran out of gas".

It won't restart until I put in that gallon from the gas can.

At the time it stalls, the engine sputters as if it is running out of fuel. So, the fuel is definitely not being delivered when there is about 1/2 of a tank left over.

I (and the Mercedes guys locally) don't think the fuel pump or relay is bad...since both work fine until 7 gallons are left in the gas tank.

I only found this exact problem on one other forum, and it was for a C-class...and went unanswered.

The gas light does not go on, so your problem may or may not be different. When your fuel light goes on and you rush to refill the tank, do you need to put in a full allotment? Or, do you also have a half-tank left?????

[marco402]

just for discussion.....the pick-up tube is the most logical culprit since all is well above 1/2 tank...does anyone know the shape of the fuel tank internally? I had an Audi A4 wagon that had an inverted U design..if we have any internal baffels or something like that, for anti-sloshing reasons, then I would guess that there is a restriction preventing the fuel reaching the pick-up...

[marco402]

wait a minute........couldn't the vapor recovery system, you know, the thing that causes the fuel tank to release all that vacuum pressure when you open the tank be the culprit? charcoal cannister, ect....if the vacuum is too strong around 1/2 tank it may be stronger than fuel pump pressure....next time you get near 1/2 tank....fill gas can, when car stops, release tank pressure, and see if it starts...before you add the gallon....just brain-storming here

[kiasu]

The gas light does not go on, so your problem may or may not be different. When your fuel light goes on and you rush to refill the tank, do you need to put in a full allotment? Or, do you also have a half-tank left?????[/QUOTE]


Its usually bone dry empty, but once filled up it will point the needle full..

[kth286]

Jim

How do you know your tank is not half collapsed ????

As marco402 has brainstormed, if the charcoal filter is not changed at the recommended intervals (and they often do not get changed because it is hidden in the wing) and gets clogged, it really can cause the tank to collapse.

[marco402]

i doubt collapsed is the right description....would it not be a pressure vs. suction equation?... the suction of the vapor recvry system overcoming the fuel pump pressure? could you not trouble shoot by disconnecting the suction vent from the tank, or even easier, just running with the fuel cap loose after you reach 1/2 tank?.....if it doesnt quit on you, then you need to check the char.cannister, ect. 2 cents, keep the change since you have said the tank really has 1/2 tank...

[JIM HOPKINS]

Thanks, guys. It is indeed the fuel venting system, although likely not the charcoal canister.

A rare disorder and you guys nailed it. Extremely impressive. Thank you, tons.

[bjay51d]

Nice one marco

[marco402]

[mgw_300e]

Wow Marco, I'm impressed!

[marco402]

ha, thanks, remember I do this for a living.....on aircraft, you dont shotgun parts, you inspect the problem, understand the systems, and diagnose before you start removing stuff...and with my current job, I get all of 20min. to decide if it can be resolved NOW, of will I need to delay/cancel the flight. I don't get the luxury of having the plane overnight, they just want to know when they can start boarding the cattle....moooooooo

[Gasdrinker]

When I totally fill my tank.. ($58.89 from reserve light @ $0.89 CDN) the pump stops, the tank is FULL and the gauge reads a little lower than a full tank . I just think these things can happen to any old car.

[rooney2006]

Originally Posted by Gasdrinker

When I totally fill my tank.. ($58.89 from reserve light @ $0.89 CDN) the pump stops, the tank is FULL and the gauge reads a little lower than a full tank . I just think these things can happen to any old car.

yeah, same here man. how many miles to a gallon do ya'll get? Just curious.

[marco402]

Originally Posted by Gasdrinker

When I totally fill my tank.. ($58.89 from reserve light @ $0.89 CDN) the pump stops, the tank is FULL and the gauge reads a little lower than a full tank . I just think these things can happen to any old car.

WOW if your quoting price per liter, OUCH..I'm at .69 CDN/Litre.
anyway.....
a fairly common issue with european cars, don't know about the jap stuff...usually due to dissimilar metal corrosion at the variable resistor..something about the water in the fuel, silver in the soldered contacts, and another metal (maybe copper?)....years go by and some dielectric action increases resistance---never achieves low enough ohm value to register FULL.. apperantly it is somewhat insidious by happening slowly, over time.......what was 1/2 tank 10 years ago, is now 1 or 2 gallons below 1/2 (per the gauge) something one wouldn't notice, since the fuel low light is still tripped at the same level of the float.... regardless of the 'gauge' reading...

Audi/BMW owners report good success with running a few bottles of TECHRON additive through the tank.(Autozone carries it for $2 cheaper then the Chevron station) ...usually 3 tanks in a row should do it (it DID work on my 99 A4 Avant) something in the stuff breaks down the corrosion, and you get the 2nd benefit of cleaning the rest of the system too , try that before replacing the sender unit...I dont think there are any repairable components....

[neanderthal]

possible contaminants in the tank in the area around the fuel pickup (usually the lowest part of the tank) may be blocking the fuel pickup or something.

i dont think there is anything there that R and R of the tank and a thorough cleaning (blow it out with compressed air) wont cure

[mrdoubleb]

Originally Posted by marco402

WOW if your quoting price per liter, OUCH..I'm at .69 CDN/Litre.
anyway.....
a fairly common issue with european cars, don't know about the jap stuff...usually due to dissimilar metal corrosion at the variable resistor..something about the water in the fuel, silver in the soldered contacts, and another metal (maybe copper?)....years go by and some dielectric action increases resistance---never achieves low enough ohm value to register FULL.. apperantly it is somewhat insidious by happening slowly, over time.......what was 1/2 tank 10 years ago, is now 1 or 2 gallons below 1/2 (per the gauge) something one wouldn't notice, since the fuel low light is still tripped at the same level of the float.... regardless of the 'gauge' reading...

Audi/BMW owners report good success with running a few bottles of TECHRON additive through the tank.(Autozone carries it for $2 cheaper then the Chevron station) ...usually 3 tanks in a row should do it (it DID work on my 99 A4 Avant) something in the stuff breaks down the corrosion, and you get the 2nd benefit of cleaning the rest of the system too , try that before replacing the sender unit...I dont think there are any repairable components....

lol here it is 1.40 euro a litre = 1.84 us dollar a litre = 2.15CAD a litre

[marco402]

$6.96/gal, mmmm.....we scream at the mean old oil companies for making 10 cents/gal profit, but the tax is under $1 in US and about $4.50 in Euro.....PER GALLON..who's the real thief....

[TacTownRyder]

I am having the exact problem with my W202. First it acted like it ran out of fuel with quarter tank, then with half tank. Starts and runs perfect after I add fuel. Gauge reads correct, no lights on. Tried to start after opening the cap but will not start until I add fuel. What was the fix???