Engine/Transmission (1998.5 - 2002) Crazy fuel pressures

[HillCountrykid]

Yesterday I installed a Holley black pump at the tank and changed all lines to AN-6. Last night I took it for a spin and I was very pleased with the results pressure wise. It idled around 12~13 psi and I could drop it to 8 or 9 playing around (not an exact WOT psi). This morning while driving at 65 or so the pressure was at 12 and would INCREASE when I got much over 5 psi of boost, and then start dropping at pretty high rpm's. When it increases it completely pegs the neddle on the Auto-Meter gauge. I tried bleeding the line to the sending unit and looked to see if I damaged the wire to the gauge, but everything looks fine. Any ideas out there other than a bad sending unit. The pressure does'nt fluctuate and bounce all over the place all the time. Just shoots up real high when the motor's under load. TIA.



Brian

 

[fj40dave]

I don't know much about you install... . but I just put a FP Gauge (Mechanical) in my '01... . and when I first start it, the gauge never goes over 5psi until the volt meter begins to stay closer to 14v - I can get the psi up some by turning off the heating (eliminating all electrical draw).

I know - sounds weird - but that's what happens... .

So... . thought from me is look at electrical draw or surplus???

 

[Houser]

Houser Just piping in

5 psi seems kinda low for an idle. I just put a new lift pump and mechanical guage in mine and and get a little over 14psi @ idle with the EZ installed. About 13. 5 without the EZ. I notice a slight drop in psi when the intake heater is on but not 5 psi. maybe 1psi. any time there is a load on the engine the psi will drop a little. I have a stock LP with no extra fancy lines or fittings and cant pull the psi lower than about 8 towing a 24' travel trailer WOT up a grade. sounds like you guys might just be having guage troubles.



Good Luck



Houser

 

[HillCountrykid]

15+ lbs. of pressure is no lack of fuel. Jumping from 12 to over 15 while giving it more throttle should'nt happen. I suspect something is wrong with the sending unit on the gauge, but would like to see if anyone has a different opinion. The gauge has been on the truck for 2 years and has not given me a lick of trouble until yesterday. Maybe moving things around messed it up.



On second thought, the reason I finally got around to putting the new pump on was that 2 weeks ago I was pulling my boat back from the coast and I could drop the gauge to 0 psi. A couple of days later the pressure returned to normal (13 idle and 4 WOT)and stayed fine until I replaced everything. So maybe it is a bad sending unit.

 

[HillCountrykid]

Well, I ordered a new sender, so hopefully sometime next week I'll see if that fixes it. The needle bounces about 1. 5 to 2 psi while driving, so I'm hoping that's the problem.