I have a 1991 F150 with an inline 6 cyl. About a month ago my truck started spitting and sputtering. I changed the fuel filter, plugs and plug wires. When I changed the plugs they were all loose. I could actually turn them by hand. After finishing with the work my truck purred like a kitten again. Unfortunately last night it started doing it again. I checkedmy plugs again and they were all tight and fine. Fuel filter is fine,too. This problem is mainly when I use the front fuel tank, but does it on the back fuel tank as well. Is this problem caused by a fuel pump? Or is there something else?? Please help!

 

Sounds like a fuel pressure regulator to me. A bad fuel pressure regulator can cause pressure to build up in the fuel rails and lines and damage the pumps. Sounds like one pump is worse than the other already. Do you recognize a "singing" or "whining" coming from your fuel pumps? If so the fuel Pressure regulator is probably stuck or has a bad diaphram. It is a cheap $18-$20 part and definately worth changing. Will probably perk up your acceleration and H.P. How is your fuel economy? If you are getting down to the single digits I would almost guarantee it is the problem. Eventually it will clog the Cat and cause overheating problems due too burning rich.

John