Dual tank question

[garlicbreath]

Hi all.
Just bought my first powerstroke, it's a 1997 f350 4wd.

First question for the board.
It has 2 tanks.
It was a municipal water and lighting truck.
Someone wrote with a sharpy over the rear tank fuel filler "no fuel here"
I would like to have 2 tanks for trips of course so I need some guidance on where to start looking for the problem.

I did start by putting in 10 gallons of diesel to see if it just leaks.
No leaks.
Tonight I will switch the tank selector with the truck off to see if the guage reads anything.

I am worried about just switching to the back tank and going for it because of horror stories of running a diesel out of fuel and them being a real pain to get going again, bleeding injectors etc.

If the guage reads, what would be my next step?

Also, on dual tank setups, do they have a feed and return line for each tank?
I am thinking it would be some type of 4 port selector valve, an out and return for each tank, is this right?

[sea71]

WELCOME to the site!! Not real familiar with the dual tanks, but my work truck has them, and I had some switch/solenoid that controls the switching from one to the next go bad. I could hit the transfer switch to change tanks and it would just shut down because it wouldnt completely switch over. The garage changed the part and all was fine. Hope you find out that its something simple.

[Big AL]

Next, I'd get me a catch pan (maybe a clear jug), break the line before the filter & drain some into the container so you can see what you've got.

[Big AL]

By the way - WELCOME!

[garlicbreath]

well, the guage works for the rear tank.
shows between 1/2 and 3/4 full, which is about what I put in.

Should I switch to the rear and run it for a while then pull the hose off? Otherwise wouldn't it just be fuel from the front tank?