I have a 1990 f150 5.8 XLT 4x4, I am not sure about the history of the truck, got it for $100 bucks and the transmission was messed up, so we had an extra one so swapped it out and it runs beautifully except:

There is a problem with the dual tanks, when it is on the front tank it runs great no problems, if I try to use the back tank it runs but then if I try to change it back to the front tank it will run some and then dies. It will do this maybe 4 or 5 times and then it is fine. So I am using only the front tank on it. But I would like to beable to use both tanks.
Second I noticed a clicking what I thought was under the dash board, almost like the card in the bicycle sound but it is only happening when I lock the lockers in, doesn't have to be in 4wheel drive, just has to have the lockers locked, any ides what this could be.

Thanks for the help

 

Congrats on the new truck! I had(ordered new) a 1990 F150 SB/SWB 4x2 with the handling package, 4.9 six & 5 speed trans...GREAT TRUCK....had it for 17 years! Yeah, the fuel selector valve.... those had a recall and were replaced....sounds like yours is in the process of failing. Just need to make sure the switch and wiring are good then replace it!

 

So when I went under my truck I could not find a fuel selector valve like all the videos show, is there maybe a different set up on this truck?

Is there another kind of valve that could be under there?

Thanks