Decided too get my 1997 ford 350 super deluxe
back in service.
I would start often , take for short spins, use occasionally

Kept as a back up too tow heavy trailer


Gas truck, with two fuel tanks ,


Rear tank only tank that operates.
When I switch too front, dies within seconds.
This seems too be common problem on this forum

Rear tank fuel is clean, front tank fuel is bad. ( smells )
Once I correct switching , I will drain old fuel fill with fresh fuel any additive I should use ? too clean tank ???


Used local and one tank is fine but bugging me and want too correct


This is what I have done so far
Thinking, lets do the easy stuff first


Open benzel and fuel switch on dash is easy too get too
using 12 volt tester , power too switch, middle is hot , rear is hot when I switch

Changing switch position too front tank

using 12 volt tester and wedging tester into switch , turn key on not cranking, but enough too hear pump
lights for a brief second then off.
Thinking switch is N.G. - I had extra switch in glove box .
Changed
Same issue .

Put a jumper wire from main power source of selector switch too front tank , turn key on I hear fuel pump pumping ? will not try too start due too old fuel, but I hear fuel pump pumping .
I don't know if the sound of the fuel pump pumping is the rear , it will require two people but I clearly ran a jumper from hot too the non working side of switch and heard pump.
Switch in glove box bad also ? How can I test a switch


Thinking relay,
Did the basic fuse testing and everything seemed good.
Is there two relays one for each pump ?
Not sure which relay is fuel pumps but tested all the 50 amp fuses in motor area near the master cylinder and everything lights.
Have no knowledge of testing a relay


Is there a relay between the tanks along main support rail ?




thanks