I have a 1993 6.5 with a 5 speed Manual. It surges at all speeds. I can be rolling along at 65 then a major change in engine sound and it takes off like I pushed the pedal to the floor...it sounds as if it is going lean or something. It really rattles and just takes off. It does it all speeds. I guess it is the pump, I have changed the filter regularly and am just looking for some input.

Your drawing air in the fuel supply somewhere.

Check supply pressure at the fuel filter drain cock with the truck idling first, if you have pressure than attach a rubber hose and run it in to a container and check for air bubbles. If there is no pressure then you probably need a new supply pump, bubbles could also be a supply pump problem or a problem with the pick-up in the tank.

That is good advice...

Check o.p.s.

huh?

The Oil Pressure Switch, located behind the fuelfilter housing. It powers the liftpump after start-up.


you can test it by opening the air bleed at idle. if no fuel comes out, you have no pressure.