Engine/Transmission (1998.5 - 2002) FASS II Loosing Pressure

[seagrave2001]

Hey guys I've had a Fass II on my truck for about 6 months now and when I first got it my idle pressure was around 13psi and went down to about 11psi when I got on WOT. So I called where I got it and he sent me a new spring which then put me up at 17psi idle & no lower then 14psi at WOT... Over the past few months the WOT pressure has been dropping slowy and now is around 10psi with the Comp box untapped with the fueling set to come on early. . I upgraded all my fuel line from the tank to the Fuel Filter with 3/8" hose that came with the FASS II and yesterday I upgraded the hose between the Fuel Filter to the VP44 with the Vulcan Big Line Kit and my FP is being monitored between the Fuel Filter & the VP44... .



So I am a little worried about when I tap the pump wire my FP will drop way below 10psi. From a stop pulling away from a stop sign on level ground it hardly moves at all maybe drop a pound or so... But as soon as I give it more fuel it drops to about 13psi and if I got to WOT it drops to 10psi... I have a message in to the guy I bought it from so I will ask him as well, but I wanted to see what you guys think as well. . It almost seems like there may be a restriction some where maybe in the pickup screen in the tank??? It almost has to be something in the tank because I just changed my Fuel filter not to long ago. Does anyone have any other ideas or suggestions?



Thanks, Engcogod

 

[hammersley]

Well this always makes me wonder about

the accuracy of the fuel gauge..... we always assume they're accurate and we really have no reason to assume that..... afterall they're not a certified calibrated gauge. Do you have an electronic gauge running directly off the FASS? I would try and see if you can verify these pressures..... otherwise you may in fact have a fuel restriction. A mess to deal with.....

 

[pcarlson]

I have had my FASS II in for about 15,000mi and had what I thought was pressure problems too. I will have fluctuating pressure every now and then but it was not the pump but the pressure sending unit.

 

[I SPEED]

I've been running the FASS II since this past Febuary. Approx 15,000 miles. When installed FP at idle was 18psi. WOT dropped that to 12psi.



Since then it has been declining slowly, but has leveled off at 15psi at idle and 9psi at WOT.



I have the spring but have not installed it yet. I had someone check the fuel pressure and they told me it was the sending unit for the gauge.



Based on what I've read here I'll change the sending unit first. Then swap out the spring in the fuel pump.

 

[RAJohnson]

[/QUOTE]

So I am a little worried about when I tap the pump wire my FP will drop way below 10psi. From a stop pulling away from a stop sign on level ground it hardly moves at all maybe drop a pound or so... But as soon as I give it more fuel it drops to about 13psi and if I got to WOT it drops to 10psi... I have a message in to the guy I bought it from so I will ask him as well, but I wanted to see what you guys think as well. . It almost seems like there may be a restriction some where maybe in the pickup screen in the tank??? It almost has to be something in the tank because I just changed my Fuel filter not to long ago. Does anyone have any other ideas or suggestions?



Thanks, Engcogod[/QUOTE]



I run 19psi at idle, 16-17psi cruising, and 11-12psi @ WOT with my pump tapped. I measure my fuel pressure at the bottom of the stock fuel Filter housing with a electric AutoMeter FPG. Hope this helps, I do not think you will see any lower fuel pressure when you tap the pump.

 

[VHolloway]

a good friend had the same thang happen and he removed the filter from the tank to the pump

and now it works great

but what will this do in the long run???

 

[RTillery]

My Fass11 has been ok for about 41K now but I thought I had a problem at one point. When I installed it, I had about 22lbs but it quickly dropped back and settled around 17 on my Dipricol gauge off the CP3 inlet.



It held steady for several months and then one morning it was running down to 9lbs. The engine seemed to be running ok, and I could hear the pump running so I kept an eye on it the rest of the day. That night I pulled the gauge side of the nipple off of the isolator and refilled with antifreeze. Pressure is back to 17lbs and has been normal for now for months.

 

[I SPEED]

a good friend had the same thang happen and he removed the filter from the tank to the pump

and now it works great

but what will this do in the long run???

I swapped out the inline filter yesterday, as well as installing the new spring. Fuel pressure increased to 18psi @ idle. I wonder if it was the spring or the filter that affected this?