Just bought a 1997 f350 crew cab 7.3 L. Has low power checked fuel pressure and it fluctuate between 35 and 60 is this normal.

 

What type of gauge are you using, does it fluctuate while idling or is it between acceleration and cruising speed

 

It fluctuate at idle and at 2000 rpm I used a mechanical gauge

 

I would suggest checking the components such as the fuel filter and line for leaks or holes or rust. Maybe you need to replace the fuel filter or check where the components meet for possible leaks.

 

If it is a steady pulsing that is perfectly normal. The pump is a mechanical, piston style pump (on the second stage) so the pulses you're seeing are the pulses from the piston pumping the fuel. Honestly, it is best to check the pressure at idle using a stick style tire gauge. Since the peak reading is what you're looking for, the stick style gauge evens out the reading. I've used other styles of gauges (and have a permanently mounted Fuel Pressure gauge in the cab) but for a diagnostic check that really is the easiest, cheapest method for measuring the pressure.