FASS 150...nothing but problems
 

Alright, so I'll start from the beginning - I have a 99 24v, and thought it would be a good idea to do the normal upgrades (lift pump, exhaust, etc...). Before installing the FASS the truck would crank and start with ease. Now I have a pump that has no visible leaks, loses prime, experiences cavitation at random times, and is now running at about 20psi after the needle gets done bouncing around after start up. Here's what I've done so far -
*Checked and rechecked all fittings
*removed the water separator filter and reinstalled (this eliminated the bouncing pressure, and ran at a solid 14.5psi for about 2 hours, then started bouncing again)
*5 gallon bucket test - still had a loss of prime and needle bouncing everywhere.
*replaced the water separator - again, ran without issue for about 2 hours and then started bouncing again.

Here's a video of the start-up madness:
FASS 150 Problems: http://youtu.be/lYTMatt7IIU

Have you called FASS?

I have, and they've been great so far. They requested I do the 5 gallon bucket test and monitor the voltage to the pump. Bucket test resulted in no change, and the voltage is a constant 13.8 volts. I'm just trying to avoid having to pay shipping on something that's already cost me almost 700 in purchase price, and 70 bucks in diagnostic stuff. Especially if the pump turns out to be good and its an issue somewhere else in the system. I poised my situation on a Facebook group, and so far we've narrowed it down to a possible restriction in the fuel filter causing the pump to backfeed on itself. When I first pulled the water separator the pump ran at a solid 14.5 psi for 2hrs on a 3hr trip, and started sucking air out of nowhere doing 70 down the highway. I swapped the water separator at my destination and the pump ran at a solid 16.5 psi for the rest of the day, and 2hrs into my trip back; then started sucking air again. I then removed the filter again, reprimed, and after it gets done bouncing it'll set at 20psi. Hopefully it's just a restriction in the fuel filter. If it isn't, I'll be sending the pump back in.

try and bump the starter and listen for the pump. If it sounds weird like cavitation, I had the same issue. If so, take out the return spring and stretch it out a little, and reinstall. My symptoms were the exact same plus weird pump sounds

See if it sounds like the video on here. another fuel pressure issue - Page 2 - Dodge Cummins Diesel Forum

I have only gotten it to cavitate three times - twice during the bucket test, and once with all the lines hooked up normal. Other than that, the pump is very quiet. So quiet in fact that I have to keep my head out of the truck to hear the initial prime run. When the truck is running I literally have to put my ear on one of the filters to hear it running.