Hey Guys,
I started dreaming of a larger fuel tank years ago, and this weekend was going to be the time to fab up a nice large steel front tank.
I pulled the box off, to see what I was up against.
![Image]()
![Image]()
Then I read this post
http://www.powerstroke.org/forum/94...org/forum/94-98-7-3l-general-powerstroke-discussion/203561-front-fuel-tank.html
Which got me thinking, will an SD tank fit in an OBS. I had one from my 06 parts donor truck, so I had nothing to lose. I was pulling the factory front tank anyways, so why not try and fit it up.
Here is all the tanks.
![Image]()
The SD and the OBS tank both use the rear crossmember for anchoring, but the SD uses a different one for the front. It still lines up, but it leaves a bit of a gap where the front OBS tank would mount. It has an area molded to bypass that front OBS crossmember, but it sits 1/2 inch away from it.
![Image]()
The SD tank also extends farther rearward than the OBS tank.
![Image]()
This proved problematic, since on an SD, the shock on the drivers side is behind the axle, but on an OBS its in front of the axle. The tank ends up being about 1/2 inch away from the shock once mounted in place. It was closer when I started, but I put a bit of an angle on the tank, and that gave me more room.
So, the tank fits, but the sender is another story. The angles of the supply and return lines make the existing OBS fuel lines completly in the wrong spot.
I had to modify the SD sender, by bending up the alignment tabs, to rotate the sender in the hole, to allow the pickup lines to line up. This meant adjusting the direction of the fuel level sender. I had quite the gong show trying to move it (broke the SD sender, welded on an OBS sender, it was in the wrong spot, cut it off, did it again, bent the SD wire to fit the OBS sender) it just seemed nothing was working right). In the end, I got it where it needed to be.
While the sender was out, I also did the Harpoon mod on the tank:
Welcome to guzzle's In-tank Harpoon Mod Web Page.
The SD and the OBS fuel sender weatherpack connectors are the same, but the pinout is different. I dismantled the connector, and moved the pins to where they should be on the OBS.
![Image]()
After putting the sender in the tank, I wired it up and turned the key on. I wanted to see where actual empty was in the tank. The sender sits about 1.5" from the bottom of the tank so there is still quite a bit of fuel at under the red on the fuel gauge.
![Image]()
I then strapped the tank into the truck, so I could start fabbing up tank straps. I dont recall completely, but I think the skidplate on the 06 was the tank holder. Since I was impatient and was cleaning up the yard, I scrapped the skidplate for the tank. That was very unsmart on my part.
Fabbing the straps were more difficult than I thought, but I figured it was because I used a 12gauge steel strap that was 3" wide. Its way overkill, but I dont want this tank falling out either.
![Image]()
I welded nuts to the bottom, so I can fab up a skidplate later. I want to prove the tank is good, and everything works before getting to involved.
I painted the straps, and shut it down for the night. Tomorrow I will put in the straps, and get the lines hooked up. I will take more pics of where the tank lines up after everything is installed. I am intrigued to see how much it holds, Im hoping its at least a 28 gallon tank. I would be ecstatic if it was the 38 gallon tank.
I started dreaming of a larger fuel tank years ago, and this weekend was going to be the time to fab up a nice large steel front tank.
I pulled the box off, to see what I was up against.
Then I read this post
http://www.powerstroke.org/forum/94...org/forum/94-98-7-3l-general-powerstroke-discussion/203561-front-fuel-tank.html
Which got me thinking, will an SD tank fit in an OBS. I had one from my 06 parts donor truck, so I had nothing to lose. I was pulling the factory front tank anyways, so why not try and fit it up.
Here is all the tanks.
The SD and the OBS tank both use the rear crossmember for anchoring, but the SD uses a different one for the front. It still lines up, but it leaves a bit of a gap where the front OBS tank would mount. It has an area molded to bypass that front OBS crossmember, but it sits 1/2 inch away from it.
The SD tank also extends farther rearward than the OBS tank.
This proved problematic, since on an SD, the shock on the drivers side is behind the axle, but on an OBS its in front of the axle. The tank ends up being about 1/2 inch away from the shock once mounted in place. It was closer when I started, but I put a bit of an angle on the tank, and that gave me more room.
So, the tank fits, but the sender is another story. The angles of the supply and return lines make the existing OBS fuel lines completly in the wrong spot.
I had to modify the SD sender, by bending up the alignment tabs, to rotate the sender in the hole, to allow the pickup lines to line up. This meant adjusting the direction of the fuel level sender. I had quite the gong show trying to move it (broke the SD sender, welded on an OBS sender, it was in the wrong spot, cut it off, did it again, bent the SD wire to fit the OBS sender) it just seemed nothing was working right). In the end, I got it where it needed to be.
While the sender was out, I also did the Harpoon mod on the tank:
Welcome to guzzle's In-tank Harpoon Mod Web Page.
The SD and the OBS fuel sender weatherpack connectors are the same, but the pinout is different. I dismantled the connector, and moved the pins to where they should be on the OBS.
After putting the sender in the tank, I wired it up and turned the key on. I wanted to see where actual empty was in the tank. The sender sits about 1.5" from the bottom of the tank so there is still quite a bit of fuel at under the red on the fuel gauge.
I then strapped the tank into the truck, so I could start fabbing up tank straps. I dont recall completely, but I think the skidplate on the 06 was the tank holder. Since I was impatient and was cleaning up the yard, I scrapped the skidplate for the tank. That was very unsmart on my part.
Fabbing the straps were more difficult than I thought, but I figured it was because I used a 12gauge steel strap that was 3" wide. Its way overkill, but I dont want this tank falling out either.
I welded nuts to the bottom, so I can fab up a skidplate later. I want to prove the tank is good, and everything works before getting to involved.
I painted the straps, and shut it down for the night. Tomorrow I will put in the straps, and get the lines hooked up. I will take more pics of where the tank lines up after everything is installed. I am intrigued to see how much it holds, Im hoping its at least a 28 gallon tank. I would be ecstatic if it was the 38 gallon tank.
