Fass Low Fuel Pressure

[DBuck]

Hi,

I have a 2001 24v truck with about 95K miles. Truck is essentially stock except for Fass 150/95 I added 1 1/2 year ago after the VP-44 ate itself. Learned a lot the hard way about limitations in stock lift-pumps and lack of stock fuel pressure gauges. At that time, I also installed the Isspro manual fuel pressure gauge with the isolator kit from Geno's garage. With Fass and fuel gauge in cab, I consistently see 14.5 psi pressure at idle, at 10 psi at WOT. I have about 10K miles on Fass so far.

Everything has been fine until about two weeks ago. I started noticing that in the mornings that is fuel pressure is a lot less than normal. It has slowly declined each morning. Now in the mornings when I start the truck, the fuel pressure is at 7.5 psi. During my 20 mile drive to work, the pressure rises steadily and gets to about 13.5-14psi (not quite the normal pressures from before) by the time I arrive. Living in the Portland, OR area our night-time temps are mild and gelling/thickening of fuel has never be a problem for me.

With 10K on the fuel filter, I don't immediately expect it to be dirty. Fass manual says 15-30K for filter changes. There have been no changes in the type of fuel (no bio-diesel, etc.) I use. I drained the water separator and the fuel looks and smells fine. Also, I have heard no change in the sounds from the pump.

I am just curious if anyone has seen similar things? I have a hard time understanding why the fuel increases as the truck (and fuel) warms up. Especially when this never occurred before. Now that the pressure is getting down to the "danger" area when cold, I need to find this.

What is the real world experience with filter change intervals? Is this the problem and I can only expect 10K on a filter?

At this point, I suspect the fuel pressure gauge. I have a fuel pressure test gauge on order from Geno's to check the pressure at the VP-44 inlet (same place as my in permanent gauge). I'll report back when I get it measured.

Thanks Everyone!