All of a sudden my 1990 f 150 starting bucking under any load..One guy says fuel pump another said water in gas and a third said fuel filter. Problem is my tanks won't switch from the rear to the front (If rear fuel pump is out can use frt). I swear one minute no problem next minute NO power...Limped it home. Was running tank low on gas..short on money these days...did have major weather change.....did put in bottle of heat.......no difference!HELP!

 

I had a similar problem on a 91 f-150. It had the 300 6 cyl. I started checking the connectors to the fuel injectors and two of them were loose. I pushed them down tight and the truck ran like a charm. I got some cable ties and secured them so that they would not come loose again. I assume you have fuel injection so it would be an easy place to start.