Hey all
I've been digging in the forums for a bit, and I'm hoping someone can point me to the correct information.
My truck has dual tanks, only the front works, yadda yadda. I haven't done any troubleshooting beyond flipping the switch one time and watching the fuel gauge go all the way past full and keep going and having the truck sputter and die in seconds.
My first thought is to replace the sending unit assembly and fuel pump, but I can't find the correct one on LMC truck (97 F250HD, 5.8 V8) so I'm looking for what the cross-compatibility is.
Also, while digging on LMC I noticed there was a 34 or 36 gallon (i don't recall which offhand, sorry, but it was double the size of the stock tank) available for the rear tank, but it wasn't available on anything newer than a 91. What changed? Could I possibly make it work? I'd love to have that extra fuel range, and if I have to replace a bunch of **** anyways, I might as well get good ****, you know?

Also, how in the name of sweet baby jesus does this system work? I've had a 87 and a 95 and was blessed with working tanks on each of them. I know there's a high pressure frame mounted fuel pump, and a low pressure fuel pump in each tank. Where are they connected, and what keeps them from back feeding? Is there a valve, or do the low pressure pumps determine which tank it feeds from and there's a check valve of sorts preventing back feeding? I know some of this system, but if someone could hammer it out for me I'd appreciate it. This is a work truck, it gets 11 mpg and my closest clients are half a tank of fuel away, it'd be nice to not have to stop for gas EVERY time I went out.

Thanks in advance.

 

The 87 has a check valve in the high pressure pump on the frame. When a low pressure pump runs it will switch the selector valve on the frame to set it up for supply and return of the running low pressure pump.
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This explains how the fuel system on your 1997 truck works: https://www.ford-trucks.com/forums/1...l#post19774757

This thread has some information for installing a 38 gallon tank in the rear position: https://www.ford-trucks.com/forums/1...2-96-97hd.html

Some of the photos are obscured because the OP no longer has a Photobucket account. Bob expired a few years ago

 

The 95 has just a pump module in each tank with no pump or selector valve on the frame.
The running pump module will open its return shuttle valve and supply the pressure to over come its HP check valve to supply fuel to the engine.

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Thanks to both of you!

If I'm understanding correct, it would appear I can order myself a 38 gallon tank and a new fuel pump and everything should hook up nicely. I appreciate yall!

 

Sad days, they no longer make the 38 gallon tank, I guess I'll have to live with the 18 that came with the truck.

That said, I'm sure there are plenty of good guides in here for replacing the internal fuel pump on a '97 F250HD (should be the same as any other 92-96 truck, correct?)

I'm ordering a Carter P74107 fuel pump for the rear, unless they're problem prone? (it was the only one on rock auto that wasn't an "economy" option, but also wasn't Delphi and $150)