I have the Isspro Performax gauges and my fuel pressure gauge started doing something strange. It works fine while driving but when I come to a stop it slowly drops all the way to zero and the slowly goes back up to normal level. The truck does not run any different. I have a Airdog 150 and it does not seem to sound any different either.

 

Can you hear the pump running during this time? is that what you said doesnt sound any different? or the truck? Because My FASS does this too at low fuel tank level. The draw straw may not be all the way down where the stock one was, and when it sucks air, it cavitates and your pressure drops because the pump isnt made to compress air like it is a fluid.

 

Nope, plenty of fuel. My draw straw goes all the way down. I have run my truck down to E and it runs fine. Truck and pump sound the same.

 

I can run my truck down to E as well, runs fine however any time I get less than a quarter tank my fuel pressure will drop then slowly rise again. If I park and shut the motor off with less than a quarter tank I have longer start times as well. If you do a search you will find lots of people with issues the same as yours. I too spent lots of time to make sure the draw straw was sitting on the bottom of the tank with a slight bevel. I think many have this problem due to installing the draw straw while the fuel tank is sitting on the floor ( like I did) rather then installing the straw with the tank suspended in the truck. JMO

 

Yeah, I thought about that when I installed mine. That is why I installed the draw straw with the tank on the truck with about a half of a tank of fuel so that the tank had the full bow at the bottom. I'll have to keep an eye on it to see if it does it when the tank is low. Maybe it has been doing it and I just noticed.