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Garage => Test Drive => Topic started by: WrightSounds on 26 November 2012, 09:06 AM

Title: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 26 November 2012, 09:06 AM
I recently purchased a 1980 300SD from a guy that had bought it from his uncle who had purchased the car new. His uncle was a WWII fighter pilot which translated on the Interstate to, "once he got on the road with his car, he didn't like to stop", so he had a 17 gallon reserve fuel tank installed into the trunk. So he had almost 40 gallons of fuel when filled up. He used to drive from Ohio to Florida... without stopping. It's gravity fed down into the standard fuel tank. The little red lever opens and closes the valve.

Anyway, I though it was pretty cool but a month later I'm thinking I'd like the thing removed. One reason beside it taking up a good portion of trunk space is that it's blocking access to the vacuum supply tank in the trunk. My central locking system isn't working and if that's the problem then I'll have to remove the tank to get to it.

Anybody ever seen something like this? IDK, maybe it's fairly common?

(http://gallery.w116.org/dl/41552-1/2012-11-25+15_15_00.jpg)

(http://gallery.w116.org/dl/41557-1/2012-11-25+15_15_33.jpg)

(http://gallery.w116.org/dl/41565-1/2012-11-25+15_26_49.jpg)

(http://gallery.w116.org/dl/41561-1/2012-11-25+15_16_22.jpg)
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: adamb on 26 November 2012, 09:21 AM
That's the most bizarre and IMO pointless addition to a W116 ever. Combined with the fuel economy of a 300SD, the standard 96 litre tank is plenty big enough giving a range of about 500 miles. And you've got to stop to take a piss anyway. Is there an additional container between driver's legs?  :o
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 26 November 2012, 10:53 AM
Is there an additional container between driver's legs?  :o
Ha! No, but I'm thinking he should have had one installed for his poor wife that rode shotgun with him on those 1,000-mile road trips.

I'm right there with you adamb. It's gone from a novelty to completely superfluous in a few short weeks. I'm wondering how I'll plug the holes
that the tubing is going through?
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: s class on 26 November 2012, 10:55 AM
My red 6.9 has an apparently factory second tank behind the standard one. 
No change-over taps etc - its seamless, and gives a total of about 150 litres - which is only about 500 to 600km range when driven hard, so it does make sense......
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: JasonP on 26 November 2012, 12:28 PM

It'll be good for days like this ....


http://www.youtube.com/v/hirZFmRwXvE

Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 26 November 2012, 07:25 PM
Ha! Well that's what most of my days seem like here so maybe I should keep it in there!
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: oversize on 27 November 2012, 02:52 AM
My red 6.9 has an apparently factory second tank behind the standard one. 
No change-over taps etc - its seamless, and gives a total of about 150 litres - which is only about 500 to 600km range when driven hard, so it does make sense......

I'd like to see that setup!!!  Most MB fuel systems have a 'reserve' tank, but I'm not sure I understand the concept....
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: oversize on 27 November 2012, 02:55 AM
Spillage on that custom tank would make one hell of a mess and it wouldn't be permitted here....  Unless you're planning regular long drives and hate re-filling to the power of 10, I'd remove it and regain some boot space...
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: wbrian63 on 27 November 2012, 04:46 AM
17 gallons of diesel = 121 lbs (267kg) of additional weight to haul around as well.

In the 80's, I had a friend that purchased a late 70's Cadillac Fleetwood sedan from a former over-the-road salesman. It was equipped with the horrible GM converted gas-to-diesel engine. This fellow apparently didn't like to stop either, so he had two tanks in the trunk, one on each side of the spare tire.

I think "in those days" the availability of diesel was limited compared to today - that was probably some of the justification for the extra tanks.

For those uninformed, large GM sedans of that era had the gas tank mounted under the floor of the trunk, between the frame rails. The filler neck was reached by hinging open the rear license plate. The spare tire mounted on the "shelf" where the trunk floor rose up to follow the frame rails over the rear differential. In a full size car like this Cadillac, that left about 1 foot of space on either side of the tire.

The add-on tanks attached to the floor of the trunk and were contoured to follow the shape of this shelf, filling in the vacant space to the left and right of the tire.

Each tank held 10 gallons, which when added to the 26 gallon capacity of the main tank, provided nearly 1,000 miles of range between fuel-ups.

The installation was really cool becaused it used otherwised unusable trunk space. Not that the Cadillac suffered from a shortage thereof. Anyone shorter than 6 foot tall would have to crawl into the trunk to unbolt and remove the spare in case of a flat - that's how deep the trunk was.

This is one of the great things about diesel that is not available for gasoline-powered cars without special provisions: no need for vapor recovery, so the tank caps are sealed tight. The extra tanks in the Cadillac were gravity fed into the main fuel tank, with no valves required. You filled the main tank, then put the cap on and filled the extra tanks. They fed the main automatically. The fuel gauge would remain on Full for about 400+ miles of normal driving.

Of course, if you were stupid or otherwise uninformed, opening the cap on the main tank before the fuel gauge had begun to drop from Full meant a flow of diesel fuel out onto the ground and onto your gucci's...
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: JasonP on 27 November 2012, 06:06 AM
I think "in those days" the availability of diesel was limited compared to today - that was probably some of the justification for the extra tanks.

(http://meandmymercedes.ucoz.org/_ph/10/441676387.jpg)

Copyright 1978, it came with my 1979 300SD.

I always try to go to the high-traffic diesel stations, to avoid diesel that has been "sitting" for a long time. My sister thinks that is silly, given how many people own pick-ups and farm in Kansas, but it is probably some wisdom from the days of yore.


Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 27 November 2012, 12:09 PM
I was thinking the same thing wbrian63... the extra weight. That's like two more kids in the backseat (I'm fine with just one for now :)
Plus the weight of the tank itself. I'm definitely going to take the thing out. I'm just wondering how I'll fill the two holes that were drilled for
the hoses that lead to the standard tank?

Thanks again for the input everybody!
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: andyatcrux on 27 November 2012, 12:42 PM
I own a 1980 300SD that has a reserve tank installed as well. It is fed through the same fill neck as the standard tank. At first I thought about removing it too. However, it has been useful for filling with the high quality B99 that Sequential sells here in Portland when the prices drop momentarily. I have saved $100 this year by being able to source it out at opportune times. Also, I am considering installing a switch to allow me to transfer over to B20,B50, or plain #2 diesel depending on temperature. Here in Portland it is possible to run on B99 almost year round with this setup. When diesel shot up to $4.60 here I was getting the B99 for $3.99 and will be getting a $.50 tax credit per gallon. That said, I do sometimes wonder about the possibilities of extra trunk space. If you do pull it, sell it. It will garner a pretty penny here in Portland.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 27 November 2012, 02:01 PM
That's the only thing we're (my wife and I) are still debating. The loading up on cheap gas when it happens. I'm still even learning about biodiesel. If I were to use that all the time is it recommended to change the hoses? Or is that only if converting to veggie oil fuel? I'll have to read about all the different sequential flavors. I've got a lot of reading to do! Thanks again!

Is your W116 White?
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: andyatcrux on 27 November 2012, 02:40 PM
Biodiesel is a solvent. People often change to viton hose. I haven't. I have only changed the return lines and the "cigar hose" under the hood. They were slightly soft and weeping fuel. I did this before using the B99 and have not had to change the lines since in the year that I have owned the car.  Even Viton hose will wear out, so I am not a fan of the higher cost. Any wear on the hoses is very slow and easily spotted. Order extra hose from Autohauz and change as needed. You would need some fuel filters too if it has not been on Biodiesel recently. The stuff cleans the engine out. You will find good information all over the net. One thing I am planning on doing is adding an additional fuel filter to help with water separation. It has not been high priority due to the quality of B99 we have here having a very low water content for biodiesel.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: andyatcrux on 27 November 2012, 02:42 PM
"Is your W116 White?"

It is a tan kind of color.....
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 27 November 2012, 05:11 PM
When diesel shot up to $4.60 here I was getting the B99 for $3.99 and will be getting a $.50 tax credit per gallon.

Andy, what is the .50ยข/gal tax credit about? Is it for using Biodiesel?
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 27 November 2012, 05:17 PM
Just read about it on the SeQuential site. Very cool.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: ZCarFan on 27 November 2012, 05:51 PM
Hmm...  short of an apocalypse, I don't think it is necessary but looks well-implemented.  When I was a bit younger, 500 miles in one shot was easy, not so much now. :)  My LeSabre would do just about that far on a tank though. 
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: Casey on 14 February 2013, 07:42 AM
I have a very similar tank I pulled from a junk yard.  It's not pointless at all.  In many parts of the USA, diesel stations are much harder to find than gasoline.  Besides which, I'd rather go to a station as infrequently as possible, and then get stunned looks from the cashiers when I prepay with cash and they see that it actually takes $200 in fuel when I come back for change. :P

If you don't drive that much, these also can make a lot of sense as you can fill up whenever the ever-fluctuating gas prices drop, and just skimp by on a few gallons when they're high.

Mine does not have a separate filler cap though - it just fills when you fill the main tank by gravity - there's a ventilation tube that comes from the top center of the tank to a hole drilled behind the regular fuel door.  I don't think you should need  to use the extra cap to fill yours - just loosen it to allow air to escape while filling the main tank - gravity will take care of the rest.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: Casey on 14 February 2013, 07:44 AM
17 gallons of diesel = 121 lbs (267kg) of additional weight to haul around as well.

...which won't make a lick of difference to fuel economy or performance in a 4,000lb car anyways.  I once loaded a couple *thousand* extra pounds (at least) in my first Mercedes diesel (a 1976 W115 240D) and took a 2,700 mile drive.  No observable drop in fuel economy at all, just a little sluggish when I headed up the steep Rocky mountains...  I averaged 42 miles per gallon on that trip.

Besides which, it'll help balance out the normally front-heavy car.  Remember an OM617 is even heavier than an M117.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 15 February 2013, 09:52 AM
Hey Casey,
What would you do to remove the tank? I started a thread but haven't got any responses: http://forum.w116.org/interiors-and-exteriors/tips-for-removing-auxiliary-fuel-tank-from-trunk/

I unfortunately don't get a lot of time with the car since my wife drives it to work Mon-Fri and I work weekends. She gets home late, it's dark, raining, etc, so I don't have much time (or light) to check things out myself. And when I do have time it's very short lived with plenty of spousal-pressure. Like when i tried to change the light bulb under the gear shifter... "Do you really want to try that now... we're leaving in 45 minutes" says wifey.  :(

I feel like just pulling it out and capping the two hoses and being done with it. Any thoughts or guidance is appreciated!
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: Casey on 15 February 2013, 10:30 AM
What would you do to remove the tank? I started a thread but haven't got any responses: http://forum.w116.org/interiors-and-exteriors/tips-for-removing-auxiliary-fuel-tank-from-trunk/
[...]
I feel like just pulling it out and capping the two hoses and being done with it. Any thoughts or guidance is appreciated!

I have no idea, without being able to see how it's installed better.  But in short, if you truly don't want it, I'd be trying to get the car back to stock as possible.  Probably the hoses are spliced under the car - on the one I removed, the line that came out of the fuel strainer on the main tank (accessible from the bottom of the vehicle) was spliced in to a hose coming from a hole cut into the bottom of the trunk.  So that would mean getting a patch of metal welded in to fill that hole, along with the holes drilled in the sides of the trunk to mount the auxiliary tank to the chassis, and replacing the line that comes from the bottom of the tank with a new one that did not have the splice.  Forgive me but it's been a long time since I've been under a diesel tank, and I know that the setup is different - on the gas models a short hose comes out of the strainer and goes into a fuel filter and pump.  I forget how the diesel setup looks. :/

Anyways if you get under the car and get some pictures of the bottom of the tank so I can see what's going on, I might be able to give better advice.

Are there extra holes drilled into your main fuel tank?  If so I'd just go to a junk yard, find a replacement, and replace the whole tank.  Really not that hard of a job.
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 15 February 2013, 10:46 AM
Thanks Casey. My wife is supposed to be home early (meaning some daylight left) so I'll get some photos of it. I do think you're correct, though. I'll post pics as soon as I can.

thanks!
Title: Re: Look at this 17 gallon reserve fuel tank in my trunk!
Post by: WrightSounds on 14 May 2013, 10:07 AM
Ok, I have removed the auxiliary tank from the trunk. I replaced one fuel hose that the auxiliary tank was spliced into. I have my trunk back, and access to the vacuum reservoir thing (that IS leaking), but better yet I have a 17 gallon auxiliary tank for sale  :)

Does anybody have an idea of market value for something like this? I know it's rather desirable, especially in the veggie oil world. This is the only thing similar I've found so far: http://www.ebay.com/itm/17-Gallon-RCI-Fuel-Cell-Gas-Tank-Aluminum-Heavy-Duty-Street-Racing-NEW-RCI-2171A-/290915948182?pt=Motors_Car_Truck_Parts_Accessories&hash=item43bbf11696&vxp=mtr

If anybody has purchased or sold one of these I'd love to know for how much! And if anybody in the Portland, OR area is interested, send me a message!

Thanks,
Matt