Well, I hate doing write ups on items which are half finished which is why this update took so long (that and I've prioritized my energy to other efforts and not forum posts lately...) but alas, here is my auxiliary tank write up which will hopefully help someone in the future. Certainly not a simple bolt on mod!
First off was discovering that the diesel tank acquired is nothing specific to the Sprinter but the standard
Titan Tank Spare Tire diesel tank kit which can be purchased at any of their retailers. This resulted in one significant problem - the tank would not sit flush again the bottom of the vehicle as the cross member interfered and would have resulted in crushed tank sides if you attempted to secure the tank. So... first hurdle was to build a drop down bracket which would allow the tank to clear the cross member and be sandwiched between the body and the tank.
Bracket tack welded
Completed bracket
Bracket in place in the tank
Moving on to the next hurdle, this one was self inflicted as I placed the filler neck exactly where I wanted it and that went fine - the issue was when I drilled a hole for the piece to go through the body and back to the tank. Unfortunately when I did so, I lined it up 'straight' and thus, the hole was just a bit too close to the rear leaf spring hanger and so I had to drill another. Whoops. Oh well, shouldn't be too hard to weld in a plate to cover it (or I take the easy route and silicone in a hole plug...).
Original location of the filler neck
BAD Location
GOOD Location!
The next step was to secure the tank to the vehicle and I used a HUGE piece of redi-rod to accomplish this. I may integrate a skid plate in to this rod so I went for overkill on the sizing. I had the room so why not?
Redi-rod was cut down from this - much easier to install the tank when it could hang lower.
Installed
Next was on to the plumbing and unfortunately the supplied fitting from Titan had a pinhole leak in it... it was quickly rectified with a small weld bead but still inconvenient.
Filler neck installed
Ran in to an issue with the plumbing where the 'obvious' spot to install the supplied fitting was not going to work - there is a check valve which prevents the diesel from entering the tank from this location. Bummer, would have worked beautifully.
So, it was a bit more complicated in that I had to drop the tank, remove the fuel pump, drill a hole in the top of the tank (while reaching inside to catch chaff) and then install a fitting to allow the diesel a uninterrupted flow in to the main tank.
Location of the diesel feed line hole - I went with a nice flat area on the tank. Little did I know but it aligned with a cross member and so a bit of cutting was required to get the fitting to clear.
My fitting was a bit too long and so I made a stainless/aluminum washer sandwich to prop it up a bit - there is another washer below the aluminum spacer
After doing some fitting I trimmed down the hose elbow to be as short as I could get it - this picture doesn't reflect that but does show the overall layout.
Notch created for the fitting - unfortunately I had to make it even larger but in reality it won't affect the integrity of anything.
Wiring along the underside moving forward to the cab
Titan controller installed