Rear Fuel Tank

[grumpin]

It's my understanding that my F250 has two 18 gallon fuel tanks. I can run the front one dry and it will take about 18.5 gallons to fill it.

The rear though, will only take 16.5 gallons when I run it "dry".

Anybody else experience this? Asking before I decide whether to pull the tank or wait awhile. Plenty of other projects.

Thanks!

[Gary Lewis]

As shown here (Fuel Tanks) an 18 gallon tank was never used.  Your rear (aft-axle) tank should be a 19 gallon unit, so if it quits at 16.5 gallons then the pickup is not going all the way to the bottom.

And your front (midship) should also be a 19 gallon unit unless your truck is a SuperCab, which seems to have gotten a 16.5 gallon tank for some reason.

[grumpin]

Oh OK, 19 gallon. That's why I'm getting 18.5 in the midship tank. (as Ford calls it)

My truck is a Super Cab with the long wheelbase.

I'm going to have to pull that aft tank down sometime or another. Now I'm wondering if someone put the wrong pump and sender unit in back there.

Don't know why I thought 18 gallon, maybe from my 1994 F250 I used to have.

Thanks, Gary!

[NotEnoughTrucks]

Learned a few interesting things on that fuel tank page.

First, Bronco's were U150's?

Supercabs on the 139" wheelbase, (6' box) had that 16.5 gallon midship tank. So did regular cab pickups on the 117" wheelbase, (6' box). Looks like anything with the 8' longbox got the 19 gallon tank.

Found three unicorns as well. 17 gallon midship tank in 83/84 117" and 139" wheelbase?

I also found the rumored plastic tank which seems to be 80 only F250/350 SD with the 137" and 161" wheelbase. Seems to be references to 3 different date codes on the part numbers which suggest it may have been available as late as 1988? Also a 19 gallon and a 20 gallon version? Anyone know if this tank would fit the F150 chassis? I have never seen one, but now I know where to look.

I had never even heard of the 22 gallon midship tank that mounted external to the frame rail on the 83 model of that truck.

Learn something new every day in the Garagemahal.

[85lebaront2]

Ever since I went to EFI on Darth, rear tank takes just at 17 gals. from empty (quits pumping) front takes right at 19 if it quit on a level stretch, on a slope in either direction it will depend on what the angle was when it emptied the sump under the FPM. BTW, that one I have the sender where it is dead on. I need to drop the rear (loads of fun) and (a) check that the NAPA FPM is correct and reaching the bottom and (b) if it is trying to get the sender correct.

Front FPM is a Spectra Premium unit bought when I was doing the EFI conversion.

[Gary Lewis]

I hadn't heard of the 22 gallon tank either until I saw it in the catalog.  As for unicorns, now you can see why I don't tell people what part number tank they have.  Instead, I give them a link to that page and let them work it out.  That's 'cause it is way too complex and mistakes are easy and costly.

Bill - I'll have to do that trick of ensuring the pickup goes to the bottom of the 38 gallon Bronco tank I'm installing on Big Blue.  But I saw that another guy looked through the filler opening and was able to see the pickup, so know how to do it.

[85lebaront2]

My nice little cell phone borescope does quite well as does my older larger one for looking in the filler hole. I did that on the Chevstang to modify the Camaro pump and hanger so it sat deeper in the tank.

[Gary Lewis]

Probably just the reason I need one.  

On the FPM's, can you add tubing to get to the bottom?  Or do you have to lower the whole FPM?

[85lebaront2]

You would need to lower the whole thing down.

[grumpin]

85lebaront2 wrote

Ever since I went to EFI on Darth, rear tank takes just at 17 gals. from empty (quits pumping) front takes right at 19 if it quit on a level stretch, on a slope in either direction it will depend on what the angle was when it emptied the sump under the FPM. BTW, that one I have the sender where it is dead on. I need to drop the rear (loads of fun) and (a) check that the NAPA FPM is correct and reaching the bottom and (b) if it is trying to get the sender correct.

Front FPM is a Spectra Premium unit bought when I was doing the EFI conversion.

How do you correct the sender? My aft one is actually pretty good, The front gets to a half tank and makes a beeline for E.

Mine sounds like Darth.

[Gary Lewis]

There is no correction to/for the sender.  They have a potentiometer (wire-wound resistor) built in that frequently gets an open.  So when the slider gets to that point the gauge goes to zero.  There's really no fix to that short of at least replacing the potentiometer if not the whole sending unit.

Bill - I was afraid of that.

[85lebaront2]

Get the correct module for the Bronco tank, then everything should be correct.

[Gary Lewis]

Bill - That's the plan.  I hope it works.