ok this is my problem. I bought a ford f-150 1989 with dual tanks. The man I bought it from said they were having trouble with the switchover valve and said he replaced it ( I believe he said it was a modulator) and everything was working fine. Well the first day i took it out for a drive it ran fine but when i parked it and tried to start it back up it acted like it was out of gas. I put more gas in and got it running and drove about two miles when it sarted to act like it was out of gas again so i switched it to the other tank which i had been told had five dollars worth in it. that didnt work either so i filled the first tank up and tried again and this time i was able to get it running and it ran fine. I talked with the previous owner and he told me i could switch tanks as i was driveing so i could keep it running till it got gas from the other tank. So as I drove home I was doing 55 and decided to switch the tank and see if it would work.It seemed to have worked fine and i left it on that tank and drove it around twenty mile before it just died on me. I tried to switch the tanks back but the switch wouldnt budge. I took the switch out only to find the wires on back of the switch were melted together. Well the first thing I did was to replace these wires and switch. But now it wont start again. I have been told that it could be my fuel pumps but these are located in the tanks and I dont relish the thought of droping the tanks and puting in new fuel pumps if that isnt my problem. But I dont seem to be able to get the pumps to start in like they should. Are there any fuses that would have kept them from being fried or have they been fried and how can i find out? Or any other possible reasons this has happened. I LOVE MY FORD But im really getting tired of breacking down everywhere.

 

Have you taken a look at the on the C-channel? I believe with an 89, you have low volume pumps in the tanks, and a high volume pump on the frame rail. I am having the same problem as you are. I checked the pump on the rail, and it is all rusted, so when I get that replaced, I'll let you know if it helped.