Howdy all from the Windy City.

I just got tired of dealing with the fuel valves, pipes, lines, filter, gas tanks, tees... cleaning, draining, replacing... This week I took out the left side gas tank.

I am going to visit some junk yards this week-end and take some measurements of the XJ40 single tank. It seems it might fit in the trunk against the back seat.... yes, I will have to relocate the ecu and relays there, and make a hole to access the tank form the left side filler cap...

Has anybody done this before?

 

I can not offer any help as I didn't even know the XJ40 was a single tank setup, but please post more as you progress as this is an interesting mod.

Good luck,

Eric

 

OK, I did some homework:
XJ40 from 88 to 91 has a single tank, and the fuel pump outside.
I did check overall dims loosely from a friends car. It is a bit less than 40" wide. Approx. 12" deep and approx. 12" high.

The series3 back platform at the end of the trunk (there the ecu is) is a few inches more than 42". Between the inside face of each trunk lid hinge, there is a bit more than 41". Also, the ser3 could fit this approx. 12" deep x 12" high.

So in theory, it will fit in the same place as in the XJ40. Still, some holes will have to be done to route the inlet gas tube from the front end of the trunk (where the gas inlet is) to the top of the fender gas cover. An elbow passing through the empty-now place of the original fuel tank, will do the trick.

Also, the gas tank from a GM S-10 pick up truck seems as it will fit.
http://www.mtscompany.com/images/chevygmc/2100.jpg
It is 39" wide x 12" x 13". Best thing is that they are made of polyethylene! No rust ever. Gas inlet is on the long side. They come with the pump and level sensor mounted on top. Quick check shows the std GM fuel pump gives 60 to 65 PSI (S-10 with 4.3 liter V8). It should be ok for the v-12.
Downsize is the fuel level sensor for the gauge...

The XJ6 and XJ12 fuel level sensor shows:
Full 20 ohms, Empty 90 ohms
But the GM:
Full 90 ohms, Empty 0 ohms
So, it will be backwards...

FYI a Chrysler level sensor:
Full 10 ohms, Empty 73 ohms... an inline resistor (17 ohms) will do it for the application. Not really worry where the gauge would be at full... somewhere high or higher, but when empty, it will get the 90 ohms.

Still, looking at the GM poly tanks... the S-15 truck has a 39" x 12" x 13" size...

I will check the Dodge Ram and Dakota. Seems they are poly as well, 41" x 13" x 15".

I will double check the available dims. at the trunk of the ser3.

All these tanks above are in the 18 to 22 gallon (US) range. I just do not want to put an econobox tiny tank that fits easily, but limits my range. At least, I will keep it in the 20 Gal. range as original.

I will post more this weekend, if I get to go to the local junk yard.

 

I have been looking at doing the same, I have been looking at Fuel cells though. This is the one I think I want for mine.

19 Gallon Street Series Fuel Cell

The GM sending unit is a problem, but I thik I will change out the fuel gauge in the end.

 

what i did 16yrs ago,pic of poly. XKS tank, and pump with filter,and lines

 

What an inspiration! Thanks!!

 

If you tanks dont leak then you can replace you valves with a single pollack valve. I did this to my XJ6c about three years ago and it works perfectly. I have used pollack valves on other cars including a diesel and they never let me down. You will have to do some basic re-plumbing and some electical mods.

 

ive always thought about just using a t-piece and joining the two tanks to flow freely and leaving them to equalize naturally. filling would be an issue because you would loose a but of volume but hey for the sake of 10 liters.....
is there a major oversight ive neglected or is it simply the loss of volume when filling?

 

Just make sure to always park on a level surface ! :-)


Cheers
DD

 

I have been looking at doing this verses the single tank and really looking at it you have to be parked at a pretty extreme angle for harm to be done. The car tipping forward or back has no change in the tank level for each tank so this is not really an issue. it would be side to side that would bias the tanks to over fill one side or the other and remember the tanks would level each other so to overflow the level of fuel in both tanks needs to be over the lower most filler. The worst time would be if both thanks were full and again to reach the filler it would be a pretty extreme angle, maybe parking sideways on a San Fransico hill or something. But more than you would normally ever experience.