Fuel pressure ?

Mustang_289 · 10-10-2005, 01:06 PM

Just bringing our 331 to life, got the fuel pressure set for 38 at idle, when motor starts to rev higher, fuel pressure drops off to about 25. We've got 24 lb injectors, and a 190 in tank fuel pump.

Do we have a vacuam leak or do we have too much motor for the stock fuel system and 190 fuel pump? We will be upgrading both the fuel system and fuel pump - when we install the supercharger this winter.

Gearhead999 · 10-10-2005, 06:36 PM

If the vacuum drops off, the pressure will go up....what's the vacuum??

Jeff Chambers · 10-10-2005, 08:43 PM

24#'ers won't satisfy a healthy 331 for very long. I've tuned two nice 331 combos recently and one was pegging 30# at 5500 rpm and the other was at 90% duty cycle at 6000rpm. They're making 380rwhp and 360rwhp, respectively. On a return-style system, if your fuel pressure begins to fall off with RPM, then the fuel system isn't up to the task.

Mustang_289 · 10-11-2005, 06:19 AM

We'll check the vacuum this weekend. Fuel pressure is not going up it's going down.

Our plans are to upgrade over the winter to 60#lb, new fuel system Aeromotive, or others if anyone can suggest, with our Vortec T-trim sitting in a box ready for its new home.

Would upgrading the fuel system now without upgrading to 60#lb injectors or MAF help the problem of dropping fuel pressure? We're doing our car in stages with the ole $$ money factor.

We've got a stock fuel tank, is that return-style or not? If it's not, should we also upgrade to a return-style tank?

10-10-2005, 01:06 PM	#1
Mustang_289 Registered Member Join Date: Sep 2001 Posts: 512	Fuel pressure ? Just bringing our 331 to life, got the fuel pressure set for 38 at idle, when motor starts to rev higher, fuel pressure drops off to about 25. We've got 24 lb injectors, and a 190 in tank fuel pump. Do we have a vacuam leak or do we have too much motor for the stock fuel system and 190 fuel pump? We will be upgrading both the fuel system and fuel pump - when we install the supercharger this winter.

10-10-2005, 06:36 PM	#2
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Re: Fuel pressure ? If the vacuum drops off, the pressure will go up....what's the vacuum?? __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

10-10-2005, 08:43 PM	#3
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Fuel pressure ? 24#'ers won't satisfy a healthy 331 for very long. I've tuned two nice 331 combos recently and one was pegging 30# at 5500 rpm and the other was at 90% duty cycle at 6000rpm. They're making 380rwhp and 360rwhp, respectively. On a return-style system, if your fuel pressure begins to fall off with RPM, then the fuel system isn't up to the task. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

10-11-2005, 06:19 AM	#4
Mustang_289 Registered Member Join Date: Sep 2001 Posts: 512	Re: Fuel pressure ? We'll check the vacuum this weekend. Fuel pressure is not going up it's going down. Our plans are to upgrade over the winter to 60#lb, new fuel system Aeromotive, or others if anyone can suggest, with our Vortec T-trim sitting in a box ready for its new home. Would upgrading the fuel system now without upgrading to 60#lb injectors or MAF help the problem of dropping fuel pressure? We're doing our car in stages with the ole $$ money factor. We've got a stock fuel tank, is that return-style or not? If it's not, should we also upgrade to a return-style tank?

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