Updated 04/29/2009   How to replace the rear tank on a 94-97 OBS Power Stroke with a 38 gal tank Article writen by Bill T. of PowerStrokeNation.com

Get yourself a Spectra Premium fuel tank part # F26E.  You can also use a F26D fuel tank.  The difference between the tanks is the F26D comes with a vent tube inside the filler neck.  I found a new F26D on Craigslist cheap, so I used that one.

 

I was able to twist the vent tube out, it’s held in with 2 spot welds.

 

 

 

Modified tank with the vent tube removed

 

 

 

It’s a good idea to undercoat the tank a few days before so it can be dried by the time you tackle this project.  I did not wait and was staring at the tank drying. 

The deeper tank comes with some electrical connectors, steel tube, copper tube, spacers, washers, nuts and longer bolts.  You just need the hardware.  You don’t use electrical connector and tubing. 

 

The hard part…..removing the old tank: 

Start by unbolting the 3 – 7mm screws in the fuel door.  Loosen the hose clamp supporting the filler tube and have it hanging underneath the truck. 

You will need to get a 5/16 and 3/8 fuel disconnect tools.  Lower the tank so you can reach on the top of the tank to disconnect the fuel lines.  I had my trans floor jack around and used to support the tank while I disconnected the lines.  Don’t forget to disconnect the electrical connector.  I left the filler tube ‘til last.  I angled the tank down so I was able to reach in to disconnect the hose clamp for the filler tube.

 Modifying the sending unit: 

Get yourself some 5/16 and 3/8 tubing.  You need approximately 12” of each, you’ll use less but just in case you mess up.  I went to the hydraulic shop and bought some stainless tubing.  You can also order some stainless brake line from the companies that reproduce the brake/fuel lines.  I imagine you can also use steel brake line if need be. 

I extended the pickup and return using Ermeto compression fittings.  The pickup length depends how far down you want to extend into the sump.  I made the screen pickup to be approximately 1/8-1/4” above the bottom of the tank.  The return was extended also.  I tried putting a 90* on the return but it made it difficult getting the sending unit back into the tank.  I routed the return in the area of the screen. 

 Gauge float:

The stock float will not work, it’s not long enough.  I went to the Motorcraft supply place and bought a float for a Bronco, Motorcraft part # PS-22, Ford F0TZ-9A299-DB.  I swapped out the float unit.  You need to grind off a plastic nub to be able to get the float unit off.  Then bend the arm to your liking.

 

 

 

After you modified the sending unit, stick it the tank, take a flexible grapple, grab the float and test its path.  You can observe the path through the filler or the rollover valve hole. 

Once you are satisfied, secure the sending unit with the lockring.  Don’t forget the O-ring. 

The hard part is getting the bigger tank in.  I worked by myself and with some struggling I was able to get the tank back in.  Next is extending the spare tire rods. 

Went to fill up and 38 gals fit comfortable.  I was able to put in 39 gals and you might be able to stuff in 40 gals.  I put 19 gals in and the gauge read slightly about ½. 

Some thoughts:

•  Exhaust tailpipe might be in the way.  Mine was but was also rusted.  I need a new exhaust anyway so I cut the tailpipe out.

•  Be easier with 2 people.

•  Might be easier lifting the bed off.  Working from the top is easier.

•  I am going to replace the Grade 5 bolts that came with the tank with Grade 8 bolts.

 

 

Edited By Big K