Question for those with FASS System

[sag2]

One of my students installed a Fass Titanium on his 2001 truck. It worked great for about 30 miles then truck would die and not start for several minutes of trying. We put a pressure gauge on it and it pulses between 15-25, then sometimes will not pump anything until you break the line at the VP44 or the filter on the FASS. Fass is giving him the run around saying he and I don't know what were doing. Fass could not explain the surging and unstable pressure, saying essentially we were no smart enough so he was not going to explain it. Last night we removed the FASS inlet and return, placed then in a can of diesel and it did the same thing. We put a Rock Auto $8 transfer pump in the truck next and it started right up.
He is sending them the pump today, but based on how they have treated him on the tech line I don't expect much.
So what kind of pressure are you seeing, and is it rock solid?

 

[Ozymandias]

I see the same on mine and i also have a question mark about that behavior.
It only builds pressure when the engine is turning and also with jumping pressures.

 

[DHayden]

I have an AirDog on my 2001 which is basically the same thing. I had issues somewhat similar to yours. My issue was bleeding the T just before the VP44 where my pressure sensor was T'd in.

 

[Dirtbilly]

I have the FASS 150 on my 1999. Holds 18-20 psi at all times.

 

[sag2]

I was thinking it might be sucking some air at the connection to the tank but the pump did the same thing using the gas can as the source. Also I thought the whole idea behind FASS besides good filtration was the ability to remove air from the system before it reached the engine.

 

[Ozymandias]

I thought about the idea that the pressure regulation valve is somewhat sticky, that also releases the air and overflow fuel to the tank.
It's just a ball and a spring.

 

[JR]

It's been a while so memory may be a touch off, but the spring stiffness for the ball should be so that idle pressure is supposed to be 16-18 psi. So long as the overflow (return line) from pump to tank is unobstructed I don't see how it could be building that much more pressure. You have a short run of 1/2" hose basically unrestricted to the tank (again, assuming nothing is plugged).
I also don't see how air in the line could cause more than regulated pressure, less yes but not more.

The only time I ever saw a higher than regulated pressure was when my return line actually gelled. I was on a long road trip and temps were well below zero. Over the course of about 20 miles My fuel pressure gauge slowly began climbing all the way to 30 psi before I got too nervous to continue and pulled off at a local rest stop with a service station. The guy was kind enough to let me bring in my filters to thaw but upon bringing them in I found zero evidence of gelling so after some thinking pulled the return line and found a conglomeration of wax and sludge and ice packed around the spring and ball. How it froze there but not in my filters i can't explain but it sure did.
I know that's all useless info to you but just wanted to explain the one and only time I've seen those pumps build excess pressure. Any time i had an air leak it would be accompanied by all the obvious symptoms, none of which was building higher pressures.

 

[garylmoore]

My Titanium Pump builds pressure every time outside temps drop below 20 degrees. I normally run about 15 psi in the summer, winter spikes will exceed 25 psi and stay there till the temps rise.