1988 F350 Lariat Super Duty
Have changed both the fuel pumps (in tank and on frame) Truck will idle but when i try to drive it.. it keeps dying .... restarts then dies again
Any clues to where to go next will be great
Thanks

 

I had a similar issue and mine ended up being the pigtail going into the lift pump on the frame. It had corroded out most of the way so when you needed minimal amperage (idle) it sounded like it was fine but under load it would not carry enough power trough it. You can test with a multimeter set in 10 amp and putting the leads inline on the positive wire to it.

 

I have seen many times where a defective coil will do this.