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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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158 Posts
Discussion Starter #1
I just purchased a 1980 300sd at a storage suction. The owner passed away in 2010 and his wife had no idea about the car. In opening the trunk there is a massive fuel tank there. I saw a picture of the same style tank on Wiki and the caption was it was a 40 2 gallon tank. Does anyone have knowledge of these tanks. It was just used in the winter in So Fl and I cannot figure why there is such a massive tank in this car. Any ideas or info would be helpful.
 

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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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158 Posts
Discussion Starter #3
There has been no wvo in this car. It only has 113,000 miles total and the gentleman died in Sept of 2010. He was 66 when he passed and his wife has no knowledge of this cars history. She has her own Lexus and this car was only used in the winter in Ft Lauderal.
 

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1980 300SD, 1985 300D
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7 Posts
I bought a 1980 300SD last summer and it also has an auxillary tank in the trunk. The seller didn't know much about it. It was a professional installation, and I thought it was a factory option. I suspect it may have been installed here in the U.S. as the fuel line fitting in the tank took a 9/16" wrench when I attempted to tighten it. The line from that tank was severely rotted and cracked requiring replacement (my most recent disabling discrepancy), so I suspect that that line probably came from a different source than the rest of the fuel lines. I hope I can gain enough confidence in the mechanical integrity of that car to someday fill up both tanks and take a road trip.
 

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2012 Toyo Camry SE, 1987 420 SEL, 1982 300 CD (Gone but not forgotten)
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230 Posts
a blast from the past

Back in the 70's people were not diesel fuel savvy. There was a fear of running out of diesel (because it was sooo limited) so a popular after market option was to add a extra tank and double your highway range. Like you could run out of diesel (without the option of re fueling) on a major highway or interstate. Probably cost the original owners some good coin to install it.
 

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'77 6.9, 74 240D, 96 Ram 5.9L Cummins
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2,653 Posts
Can you post a picture? I have a spare fiberglass tank in the trunk of my W115 which fits in there pretty well but it doesn't eat up too much of the trunk space. I have never used it and so I think the capacity is 15 gallons. A 40 gallon tank must swallow up much of the trunk, even in a W116.
 

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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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158 Posts
Discussion Starter #8
There are 2 seperate feeds under the tanks connected. Both of the tanks have Mercedes screens in them. I have taken them out enough to recognize them. No leaks under and I finally went to fill the tanks up 2 days ago. The gauge registered slightly over half. The two tanks took 19 .7 gallons. Glad I filled them when as the price went from 3.51.9 to 3.70 today. The additional tank measure out to 20 gallons plus or minus 1 gallon.
 

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1993 400E, 1993 300TE Wagon, 1977 Euro 6.9, 1967 230S IMA Universal Wagon, 100 or so MB Parts Cars.
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195 Posts
Diesel fuel tanks will not blow up when rear ended, just sayin.
 

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1977 280SE
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11 Posts
I bought some parts from a guy that was selling W116s when they were new. He told me that during the gas crunch of the 70s, people were very afraid of rationing and so they put these massive 40-gallon tanks in these cars. He knew mine was gas so I'm assuming that it didn't matter if it was gas or diesel.

I don't think these were ever a factory option but evidently, they were a dealer-installed one.
 

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1980 300SD, 1985 300D
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7 Posts
Aux fuel tank

Here are pics of my aux fuel tank in my 1980 300SD.
It just so happened that I had a fuel leak in the hose from that tank and I installed a shutoff valve with the new line.
This car had an issue with idling rough immediately after exiting the highway as though running out of fuel. The engine would stall and die if left at idle. After several attempts to remedy, I discovered that when that tank got low/empty it would allow an air bubble to form in the filter, but only at sustained high rpm. It runs fine on the highway, but I suspect that the bubble gets pulled into the IP upon returning to idle. I discovered this by watching the air/fuel in the prefilter at different rpms. (This is my theory, anyway).
The shutoff valve was an instant fix for that problem. I may eventually remove that tank as I can never tell exactly when its going to give trouble and require the valve to be closed.
I doubt I would ever need that much fuel in between stops and I don't need to tote around fuel that I'm hedging.
 

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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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158 Posts
Discussion Starter #13
I am waiting for one of my kids to stop buy so that they can take a pic. Mine does not look anything like the one pictured. My fill goes directly into the stock tank but there is no hose visual. There are two outlets but no visual attachment between the tanks. Same type of mount to the body.
 

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AccountKiller
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179 Posts
Is it for sale? I'd have to see pictures to be sure, but I think I would really like to have this if you don't want to keep it...
 
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