This great old truck (a cherry picker) has the 7.3 liter gas engine. Prior to about a year ago, the stock A/B tank switch on the dash worked perfectly. Then one day a gas station attendant put gas in the wrong tank. (attendants ONLY can pump gas here in Oregon) I was close to empty in the tank I intended to have gas put in. Sure enough, the truck ran out of gas. I hit the switch and nothing happened! The "wrong" tank now had gas in it and I was stuck until I could get more gas into the tank i originally wanted it in! I've tried using the switch several times since then with no luck at all.

I have fairly good natural mechanical aptitude, but am definitely NOT in the class of a technician. Have any suggestions fellas...on how I might fix this problem?? Even if it's just to give a good Ford mechanic some direction...

Whatever happens, thanks for offering the free memberships on this forum. I may choose to go through the old truck at some point, and this forum would obviously be a great help to me.

Any/All replies appreciated!!

 

On the inside of the driver-side frame rail, near the nose of the front tank, there is a 6-port valve - the switch on the dash only tells this valve what to do, the motor/solenoid/whatever that is part of the valve assembly does the actual switching for you. It is possible that this motor has died, thus leaving the valve stuck on whatever tank you were using. This actually seems to be an uncommon failure mode for these things, usually what happens is they get stuck in away that they draw fuel from one tank but return to the other, the engine acts like a transfer pump in a sense... valve and motor are one assembly, and they can be replaced fairly easy, but new ones ain't cheap. You may want to look into 3-port manual switching valves (you'll need two, one for the supply and one for the return), it will likely be the cheaper and probably more reliable (in the long run) option...

 

thosevalves are around 200.00 bucks and are a chunk of junk ! if you switch to manual valves you will never again be left on the side of the road with gas in one tank and cant go any place !!

 

i have the issue with the selector valve.. can you guys recommend what kind or where you are finding the manual valves so i would have a better idea on them? thanks and sorry for hi-jacking the post from the OP

 

If the 89 is like our 88 F350 the selector valve is passive in that it uses the pressure from the little in-take pump to switch from one tank to another. The switch on the dash slects the tank pump and the fuel gauge.
Over time the passive tank switcher gets stuck on one tank. We were stuck on the front tank.
Ford had the 88 tank selector on the shelf for $286. I bought one for a newer truck and made it work.
If I was to do it over I would get a manual valve. You need a 6 port valve to handle 4inputs and 2 outputs for send and return.
A diesel tank selector valve for a boat will work.
designatedengineer.com (do a search) has valves. Expect to pay about $175. and do some electrical and plumbing.

 

this should help:

https://www.ford-trucks.com/forums/9...el-gauges.html

KindredSpirit,
7.3l (444)= diesel engine.
7.5l (460) = gas engine.

 

I lost both tanks in short order and after pulling the switch from the dash on my 88 F150 and confirming the contacts were indeed contacting as they should with an ohm meter, I headed to the transfer device on the driverside frame rail and concluded like oleman that it is passive and switches based on line pressure (look ma, no wires). My problem was that I had lost both in-tank fuel pumps and still had issues with the transfer device. I replaced one rusty midship tank, the transfer device, and one pump and dare anyone to flip the switch.

 

Oh and don't forget it may be the filter or the 3rd pump (high pressure) also located on the rail at least on the 150.