Engine/Transmission (1994 - 1998) Fuel systems upgrade

[Jim Fulmer]

We watch the 24V guys update there fuel systems and we sit back with no total system make over like they have. Who out there has changed there whole system out from tank to pump, I was even thinking about modifying the tank pickup to a bigger line. We can add braided line for pressure and return as well as the small hoses and fittings and come up with something better. I feel like my fuel pressure is about to drop allot, like Piers said your not to bad now but it can be better, I'm at 17 PSI at WOT so it's sucking a little wind.



Jim

 

[Joe G.]

Jim,



You probably need to look at your overflow valve. Mine was pretty low once so I stretched the spring. And shimmed it. When I finally got around to installing a fuel pressure gauge I found that I had overdone the spring business. Removed the shim. Now my pressure is ok, but on the high side. It was at least 120K miles ago that I stretched the spring.

 

[Deezul1]

Jim

I also did the spring stretch thing and it made more pressure. Try . 550 length and see what happens.

John

 

[Jim Fulmer]

Idle and high RPM pressures are fine, it's a supply thing... lack there of. I was thinking of all AN line with a pusher pump for the near future.



Jim

 

[Strick-9]

Jim,



I've done it. Here was my problem. All pressures were fine with my truck 20+ psi (except WOT). I put extra shims in the overflow valve and of course the idle pressure and part throttle pressures came up, but WOT would still fall off. I also don't like the idea of high pressures at idle with the stock lift pump. Why work that thing any harder 95% of the time when you don't need the pressure.



My fuel pressure was falling all the way down to 3psi under WOT. So I changed my fuel filter. No difference. Then I changed my lift pump. No difference. Like you, it wasn't a problem under most conditions, just when I have the pump turned WAY up.



So I installed an auxillary pump. I used an electric pump designed to run all day at 50+ psi. I have a separate filter and pickup in the tank that I ran down through the top of the tank. I have a screw on high pressure (200+ psi) fram filter and 3/8" line from the tank to the banjo fitting on the P7100.



With the pump off, I have stock pressures. When the pump turns on the pressure jumps to about 45 psi and maintains 40 psi at ALL times.



I think it's a great system myself. I don't think electric pumps are nearly as reliable as our stock pumps. So I didn't want a system that relies solely on an electric pump. I also didn't want to give up my fuel heater. I don't like cranking the pressure on a stock system all the time by shimming the overflow valve because it is harder on the lift pumps and causes premature failure.



This way, I have a system with the fuel heater, just as reliable as stock and when I need excess fuel volume I flip a switch and have it available.



I haven't dyno'd it to prove anything, but the barrels on a P7100 will fill faster with 40 psi of pressure than they would with 3 psi of pressure. So it SHOULD help at high fueling rates and high rpm.



-Chris

 

[illflem]

Most folks who have installed pushers have had to remove their fuel heater, it's on the suction side, not designed for pressure and will leak. Same thing goes for the mechanical pump. Think it was Jannety who experimented with higher pressure to the injection pump and didn't get any more power out of it.

 

[Jim Fulmer]

Chris, that was the idea I had but didn't have that way pictured, makes sense to me. I guess the only other questions are how did you tap into banjo bolt area and do you have a check valve in that additional line to keep it from being pressurized with the stock system and on the tank pickup did you run a new hard line all the way through to the screen at the bottom of the sending unit.



Jim