Author Topic: Weird experience refuelling...  (Read 4040 times)

The Warden

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Weird experience refuelling...
« on: 01 May 2006, 10:49 PM »
Hello!

I went and refueled the 116 for the second time, on Saturday night. Partially because I believe that full tanks are happy tanks and partially because I've found that this is the best way that I can most accurately calculate my fuel economy, I'm in the habit of filling the fuel tank right up to the brim. On the 123, this can take me upwards of a half hour, because diesel fuel tends to foam up and I have to wait for the foam to die down. The presence of the foam means that, if you simply fill up until the pump clicks off, you won't get the fuel up to the same level every time (this is why one of my reasons for doing this is to calculate the fuel mileage accurately). Also, getting the fuel all the way up to the top of the fillneck means getting an extra 2 to 3 gallons in the tank as compared to stopping when the pump shuts off.

So, I went and fueled up the 116 like this...and came across a surprise. With every other diesel I've ever owned, once you get the fuel to the top of the fillneck, the tank would then "burp", the fuel level would go back down, and repeat the process maybe 7 or 8 times. The 116 was different. Once I got the fuel up to the top of the fillneck and the standard burping finished, the fuel level would SLOWLY surge down until the level was just barely visible...and it kept on doing this, even after topping it off countless times over the course of almost an hour. Fortunately, it was late at night so there wasn't a wait for my pump...

I at first assumed that the tank vent was plugged or something on those lines, and it was even more difficult than normal for air to get out of the tank. Then I saw that I had pumped 22 gallons into the tank. :o I was under the impression that the 116 had a 21 gallon tank, and the fuel gauge at least SEEMS to be reading accurately...it isn't swinging wildly, and the car was driving like there was still ample fuel in the tank, and I fueled up at 1/4 tank remaining (483.3 miles on the trip odometer). BTW, the pump first clicked off at 18 gallons.

So...is the 116's fuel tank a weird shape, or could the fuel have been going somewhere else? I actually checked the trunk and the rear footwells (as well as under the car) to make sure that fuel wasn't overflowing into somewhere that I didn't expect.

I know this is somewhat odd, but any thoughts would be greatly appreciated...

Thanks in advance :)
1979 300SD (W116.120), miles unknown, daily driver, keeping her on the road
1984 Ford F-250 6.9l IH diesel

michaeld

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Re: Weird experience refuelling...
« Reply #1 on: 01 May 2006, 11:18 PM »
Warden,
Wow.... and I thought my Saturday nights were boring! (Just kidding ;D)

You are (sadly... sigh :'() underestimating how thirsty your girl is.  If your 116 is like my 450SEL, your total tank capacity is 25.3 gal (US) including a 3.4 gal reserve.

Hope that helps,
Mike

The Warden

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Re: Weird experience refuelling...
« Reply #2 on: 02 May 2006, 12:28 AM »
I'm one of the most anal SOB's out there when it comes to keeping a log of everything... ;D

And, I didn't realize the tank was 25 gallons. So, maybe things are okay other than the vent being clogged? I hope that this means that I didn't get the tank all the way full on the first fueling (and I don't think I did; I didn't catch the "surge-down" until after I had put the nozzle away the first time)...but, if by chance I did get the tank all the way full the first time around, this means I only got 21mpg...which is lower than a 617 should be getting...
1979 300SD (W116.120), miles unknown, daily driver, keeping her on the road
1984 Ford F-250 6.9l IH diesel

OzBenzHead

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Re: Weird experience refuelling...
« Reply #3 on: 02 May 2006, 05:10 AM »
Warden:
Quote
I was under the impression that the 116 had a 21 gallon tank

Yup - 21 Imperial gallons; that's about 25 US gallons.

116.025

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Re: Weird experience refuelling...
« Reply #4 on: 03 May 2006, 05:31 AM »
Warden:
Quote
I was under the impression that the 116 had a 21 gallon tank

Yup - 21 Imperial gallons; that's about 25 US gallons.

Warden, in the case of your SD, you are essentially correct.  The SD's tank was 21.7 US gallons, or 82 liters, according to Nitske's Production Models 1946-1995  book.
Chad Johnson

'77 280SE Euro (4-Spd) Sold 1/5/09
'71 220D (4-spd)
'77 280SEL Euro (4-Spd) RIP
'89 420SEL
'78 350SE Euro
'86 300E 5-Spd RIP by Chevy S10
'83 380SL
"Don't Worry, Bobby, even a worn out Mercedes is better than a 2010 cracker-jack box

The Warden

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Re: Weird experience refuelling...
« Reply #5 on: 03 May 2006, 02:14 PM »
So, the diesels have a smaller tank? Or do the SWB 116's have a smaller tank than the LWB 116's?

Or, could the book be off by chance? I ask because the tank size you list is almost the exact same as the W123 chassis (which has a 21.1 {or 80L} gallon tank)...

Thanks again 8)
1979 300SD (W116.120), miles unknown, daily driver, keeping her on the road
1984 Ford F-250 6.9l IH diesel

OzBenzHead

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Re: Weird experience refuelling...
« Reply #6 on: 03 May 2006, 05:44 PM »
Warden: I can't argue with Chad about the tank size on diesel 116s because I have no direct diesel experience.

However, my 96-litre tank is on my SWB 116, so that doesn't seem to be the right theory.

Whilst keying that sentence, it occurred to me to refer to this forum's great library resource; on the page http://www.w116.org/library.php?116_120 it lists the tank size for 300SD as  96 litre.

michaeld

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Re: Weird experience refuelling...
« Reply #7 on: 03 May 2006, 08:57 PM »
US gallons, Imperial gallons, liters...  Thank God I bought a fancy H.P. business calculator that does conversions or I wouldn't have a danged clue what you European fellers were talking about!

From your typically isolationist, arrogant, narrow-minded American neighbor on the other side of the ocean.
Mike

The Warden

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Re: Weird experience refuelling...
« Reply #8 on: 04 May 2006, 01:43 AM »
US gallons, Imperial gallons, liters...  Thank God I bought a fancy H.P. business calculator that does conversions or I wouldn't have a danged clue what you European fellers were talking about!

http://www.megaconverter.com/mega2/

I use the above site to do my conversions; works beautifully thus far :)

FWIW, 96 litres = 25.361 gallons. :)
1979 300SD (W116.120), miles unknown, daily driver, keeping her on the road
1984 Ford F-250 6.9l IH diesel

116.025

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Re: Weird experience refuelling...
« Reply #9 on: 04 May 2006, 05:04 AM »
So, the diesels have a smaller tank? Or do the SWB 116's have a smaller tank than the LWB 116's?

Or, could the book be off by chance? I ask because the tank size you list is almost the exact same as the W123 chassis (which has a 21.1 {or 80L} gallon tank)...

Thanks again 8)

Nitske's book is usually on target, but there is the occasional misprint.  I think for some reason, they put smaller tanks on the diesel S-classes, because if memory serves, the 126 chassis 300SD has a 23 US gallon tank, whereas say, a 380SE had a 25.361 US gallon (thanks Warden  ;)) tank.  In my experience, Nitske's book has been good with the fuel tank size, I've made it into some stations by the hair on my chin based on the numbers in his book. 

Also, if you have the owners manual for your SD (or someone with one pipes up) it should tell you in there.

Gordon: Good point about the reference on this site.  I'd still be surprised if the SD had the same size tank as the gassers, but I could be wrong, it's happened before.  ::)
Chad Johnson

'77 280SE Euro (4-Spd) Sold 1/5/09
'71 220D (4-spd)
'77 280SEL Euro (4-Spd) RIP
'89 420SEL
'78 350SE Euro
'86 300E 5-Spd RIP by Chevy S10
'83 380SL
"Don't Worry, Bobby, even a worn out Mercedes is better than a 2010 cracker-jack box

The Warden

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Re: Weird experience refuelling...
« Reply #10 on: 07 May 2006, 12:09 AM »
Just a word of warning, however. A friend of mine with a 6.9 kept on topping up with the result that, somehow (?) the fuel found its way into the charcoal canister located next to the radiator, and he finished up shelling out $A200.00 for a new canister.

Yipes!! Good thing diesels don't have that charcoal cannister, eh? ;)
1979 300SD (W116.120), miles unknown, daily driver, keeping her on the road
1984 Ford F-250 6.9l IH diesel