Toyota Repair: camry fuel problems, fuel problems, fuel pressure

Question
Hey Ted,
I have a 89 model camry and have recently had problems with what i believe to be a fuel line/pump problem. The car will run then after a few minutes will begin losing acceleration, sometimes it will then regain momentum and run fine for a bit but then will soon again loose acceleration and eventually stop, as if the fuel isnt pumping properly. I have tried clearing out the lines of any obstruction and changed the fuel filter, however am unsure as to what to do next, if it is the fuel pump why would it work sometimes and not others.
Any help would be greatly appreciated,
Regards,
Ray

Answer
There could be a restriction inside the tank at the fuel pump pickup screen, this could be caused by rust or other debris or even water in the tank, the first thing that should be done is to measure the fuel pressure while driving with a pressure gauge connected that is visible by the driver, if the fuel pressure drops when the problem occurs then either the pump is going out or there is something in the tank that prevents sufficient fuel to be delivered, if the pressure doesn't drop then it's not fuel related and more diagnosing is needed.