Either the pump is gunked up from gasoline residue or the brushes are wearing out in the pump. We took the pump off of a 280SE 4.5 and set up a gallon bottle with two hoses, Purple Power solution, and a power supply and run the pump both forward and reverse and flushed a WHOLE BUNCH of gunk out of it. If that doesn't fix it, then the brushes are worn and you'll have to get a new one or a better used one.