Engine/Transmission (1998.5 - 2002) Fuel pressure

[Kalaehina]

Another fuel pressure question, I have a stock 2001 HO 6 speed with 55,000 miles on it. I relocated the lift pump to the frame of the truck and replaced it with a FASS fuel pump. After doing a filter change in June I noticed my fuel pressure gauge (Westach with electric sending unit mounted on filter housing) would give readings between 15 (idle) and 11-12 cruising on the freeway (60 mph cruise control on). My concern is that before the filter changes the gauge would read 15 all the time, no matter what position the throttle or load was at, then today as I was reversing into a parking stall at idle I noticed the pressure dropped to 13. When I started up a few minutes later the pressure had returned to 15, and dropped back to 11-13 as I drove away. I've only had this truck for about a year now, so gauges and pump is about the same age, I put on about 17,000 miles. I plan to change the filters again just to be sure I didn't get a bad filter, I also double checked the electrical connections at the sending unit, they seem tight and wiggling them didn't make the needle move. Where else should I be checking? Any advice or suggestions would be greatly appreciated. Thanks!

 

[Sticks]

I have not seen 15psi on my FASS 150 for years. I see 14 at idle, 12. 5-13 on the highway, but never lower.

A lot of possibilities.

I would verify the fuel pressure with a mechanical gauge first. You should have your fuel pressure gauge mounted to take readings at the VP - outlet side of the final fuel filter, or right at the VP inlet banjo bolt.

Is the FASS the 150 (one of the ones with the filter mounts in the housing) or the DDRP?

Your sock at the pickup tube in the tank may be getting restricted.

Relief valve on the VP may be worn out.

You might have some fluctuating voltage or high resistance powering the FASS - AKA Voltage Drop. It's amazing what a little corrosion will do to an electrical circuit.

 

[klcammie]

Is your sending unit the older style? About 3in long and 1 1/2 in diameter. Mine was giving weird readings up down, called Geno,s where I bought mine. They have been having problems with that style and have gone to a newer style. Changed it out and have been happy since.