Fuel Pump Pressure ?

[mike uz]

What should the fuel pressure be at idle and at WOT? the fuel pump is a stock lift pump ( original ). you can see the mods. done to the truck in my sig. i did have a problem with the return line valve, i replaced it with a new one a week ago and it made a huge differance in the performnce , since it read 0 on the guage. the new return valve jumped it up to around 20 to 25 PSI at about 2000 RPM. also can i shim that valve if the pressure should be higher? some times it runs like a bear , and next time it runs like a cub . just trying to get this thing tuned its a new build. THANKS FOR ANY AND ALL THE HELP. mike

[joe03dodge]

That sure sounds like a lot of pressure for a stock lift pump. a air dog only runs around 20 at idel. I am not sure on stock pressure.....

[Dual K20s]

Thats decent, but I'd check your lift pump. with the truck idling pinch the fuel return line closed at the rubber part. The fuel pressure should immediately start climbing to peg the gauge, if it doesn't then your lift pump is dieing. Shimming would be fine, if the overflow is the problem

24 valves, and CR's are totally different animals. And Airdogs along don't make enough pressure either, you have to run an AD with a raptor FASS 95,180, and 200 pumps are fine.

Stock specs You want at least 17psi @ idle and 25+ @2500 rpm no load.

P-pumps make there best power when feed @45psi and power significantly starts to drop if you go below 20-25psi

[mike uz]

Dual , can you get a stock lift pump to feed the p- pump 45 psi ? or is that useing a aftermarket set up regulated at 45 psi. thanks mike

[Dual K20s]

Cruising the pressure is not a problem, its volume at WOT that you will struggle with. The stock setup probably won't be able to pump enough volume to maintain the 45psi at full tilt. A small pusher pump, Holley blue/black are popular, that supplies the stock pump so all it has to do is pressurize might get you close. Under 500hp a healthy stock system seems to do okay and most wouldn't worry about messing with it.

What kind of WOT pressures do you see? Shims may help, but if the pump can't keep up, ridiculous pressures at idle won't do you any good. Try to keep the max psi to the pump below 50psi for reliability if you can.

[mike uz]

Thanks Dual, I am going to get alittle better guage hooked up on mon. and see what going on at wot. under a load. i do have a couple of holly blue+red pumps around, If i hook one up should i feed the lift pump or just run it to the p-pump and reg it at around 40-45 psi. Is there a problem hooking it up directly to the p-pump ? Also i read joe g fuel system artical i am going to check for the air leaks and get rid of the heater. this is the original lift pump on the truck 248,000 mi. I also did the return pinch hose test and the pressure shot up to 45+ so i assumed it was ok. I THANK YOU FOR ALL THE HELP mike

[Dual K20s]

I'm not sure if the Holley's like running 45psi, plus I hear they like to die suddenly

Feeding the stock pump I think would be easiest. If you tried to feed the stock filter you would have to find the correct banjo fitting (metric sizes might be difficult I'm not sure) to take care of the injector return. Plus if you had a problem with the Holley, it could easily be by-passed on run on the stock pump.

[illflem]

I don't know, perhaps I'm old school but considering how reliable the mechanical pumps are and how much the 24 valve guys whine about electrical pumps I think I'd stick with the stock system unless I was pushing big hp, like over 600.

[clc]

I have a FASS feeding 17 PSI to the input of the stock pump on my 96. I have 40 PSI at idle after the stock filter. The pressure drops if I turn off the FASS but the truck keeps running so I have performance AND reliability.

[mike uz]

Thanks, to all of with feed back. I wil let you know what i decide , and how well it works. mike