1988 Isuzu Trooper diesel conversion

The solution to the filler neck dilemma was to fabricate a tube to connect the new tank to the (shortened) original rubber fuel filler hose.

I began by ordering a piece of 1-3/4" I.D. mandrel-bent mild steel exhaust, something called a J-bend. This piece of tubing is used by custom header and exhaust fabricators and features a 180-degree bend and two legs of different lengths.

Next, I took a number of measurements of both tanks to determine the location of the filler necks on each. I used one of the mounting bolt holes on the tank flange as a reference point, as these holes were the same on both tanks. Using a straightedge and a long screwdriver (through the bolt hole, to obtain a reference line) I was able to measure the location of the necks fairly accurately.

These measurements were then used to generate a CAD drawing of the two tank necks. Additionally, I drew the J-bend and the rubber filler hose. All of this information was used to determine the best way to use the J-bend to connect the existing filler hose to the new tank. The CAD drawings were then printed and used as full-scale patterns to cut the J-bend, weld the pieces together and to cut the filler hose.

The filler hose was cut just after the first right angle bend (just as it begins to travel sideways after dropping from the gas cap area). The J-bend was cut into sections and tack-welded into an S-shape for initial fitting. After determining that the fit between the frame and bed support channel was too tight, I flattened the tube a bit in the middle in order to get it to fit. I also purchased a Gates universal 45-degree bent fuel filler hose, as I needed the 45* bend to connect the tube to the new tank's neck, which is at a more upward angle than the old neck.

My clumsy welding caused a burn-through during finish welding of the tube, so I coated the entire junction with J-B Weld to seal it. The final fit is extremely tight, but it works - leak free, so far.

The other difference was in the location of the overflow pipe. I had to bend it slightly sideways to get it to clear the body bed support channel, then buy a length of 1/2" I.D. fuel hose to connect it to the filler cap (the old one was too short).