how to lower fuel pressure?

[dasfinc]

I have a 98 ranger with a 98 Explorer motor in it, running a 96 ECU and 99 Returnless fuel rails and injectors

it is running PIGGGG Rich *assuming because the fuel pump is pushing 72PSI, not the 45 that the ECU is expecting*

There are no CEL codes from this, so I know it is killing my fuel mileage and power.

Any way to fix this issue without replacing the entire fuel pump assembly? Inline FPR, Etc?

I have returnless fuel rails, but I'd imagine swapping the FPR's on the rail wouldn't DO anything since the returnless FPR is at the END of the rails, so I'm not sure what kind of impact, if any, it has on controlling the pressure since the pump and rails are pushing 72PSI into the engine.

I'd read that there is a FPR inside the fuel pump? or is it a seperate thing INSIDE of the fuel tank with the pump?

HELLLLP Input????
________
health store

 

[V8 Level II]

I have returnless fuel rails, but I'd imagine swapping the FPR's on the rail wouldn't DO anything since the returnless FPR is at the END of the rails, so I'm not sure what kind of impact, if any, it has on controlling the pressure since the pump and rails are pushing 72PSI into the engine.

The item on the returnless rails that looks like a FP Regulator is actually the Fuel Pulse Damper and it has no influence on the overall fuel pressure. The FPR of the 99~01 returnless Ex is part of the intank pump unit, similar to the one in your 98 Ranger.

You're right about the pressure. The 99~01 returnless system runs at about 65 PSI constant pressure. By contrast, the 96~98 return fuel system runs at about 30~40 PSI variable pressure, regulated by the vacuum controlled FPR on the return side of the rails. The returnless system runs one step smaller injectors but there's still no way that the 96 PCM can scale back the pulsewidth enough to make it run correctly.

Using factory parts, I see 2 possible solutions for the overrich condition:

• Convert the system to return fuel using the 96~98 injectors and rails, adding a return line and a return style tank unit. OR
  
• Convert the electronic controls to be compatible with the returnless system that you have now. This would mean using a 99~01 PCM, engine harness, Cam Position Sensor and MAF. [If you are using a 4R70W automatic from a 96~97 Ex, that opens another can of worms because the wiring and controls are different in those years, making the transmission incompatible with the 99~01 PCM.]

 

[doorgunner]

I remove a section of of high-pressure fuel hose at the engine....slightly flared the ends of the steel lines at the engine and tank cuts....then installed a 3-port brass manifold...in the port that went to the engine I modified a .060 carb jet to reduce the fuel pump pressure from 70#s down to 6#s for my carb.....out of the 3rd port of the manifold I ran high-pressure hose as a return line to the fuel tank...it costs me about $35 dollars and 1 hour's work to get it done. I double clamped all hose ends where they attached to the original steel lines for safety. I also installed an in-line fuel pressure gauge into the setup on the engine side of the modification to help me get the right size jet for the fuel pressure I needed at the engine.

I would think you could do the same thing to your setup, but drill the carb jet larger in .005 increments until you get the 35#s pressure you'll need.


fuel rail}OEM regulator}high pressure hose}fuel pressure gauge}h.p.hose}3-port brass manifold (with one port with barbed fitting going to fuel pressure gauge/2nd port with barbed fitting going to hp hose connected to steel pressure line from tank pump/3rd port with barbed fitting connected to hp hose returning excess fuel to fitting installed in tank as a return line....hope this made sense.

 

[originalnitro]

you could install a vacuum controlled bypass FPR inline close to the engine.

 

[foxracing5491]

99 4.0 into 95 2.3

i have a 99 4.0 in my possession and i own a 95 2.3 already have the 4 cyl out and the 4.0 ready to go in with the ecu and wiring from the 99, but the 99 is returnless and my 95 is return. i cant put a returnless fuel system in my 95 because the body wiring is different for the returnless. i picked up a return fuel rail from the junk yard today out of a 95, so im all set with connecting the fuel lines, but what i have read the ecu from the 99 varies the voltage to the fuel pump to control the speed of the pump. so with the return fuel pump, return line and rail with a fpr on it, will the fuel pump not get the voltage and in turn not send enough fuel to the rail.

 

[breidhaupt]

install a aftermarket fuel pressure regulator that is adjustable in range of pressure that you want.

 

[JoshT]

Or try starting a new thread in the 4.0L forum, or "other engine swaps" forum instead of digging up a year old thread in the V8 swap forum.

 

[foxracing5491]

id rather digg up an old thread since people in this thread sound like they know what there talking about, and the fpr on the fuel rail i have know will regulate the pressure just fine. just dont know if the fuel pumps going to send enough pressure since the ecu regulates the voltage to the pump for the variable speed pump since theres no fpr or return line on the fuel rail of a 99.

 

[breidhaupt]

i didnt think the post was that old. besides there's nothing wrong with trying to help people out. and as for what i was saying about the fpr was that even it you couldn't put it on the fuel rail you could always cut and flare the fuel line the put it inline after the fuel filter.

 

[V8 Level II]

just dont know if the fuel pumps going to send enough pressure since the ecu regulates the voltage to the pump for the variable speed pump

Rangers do not have ECU controlled fuel pump voltage like some other Fords do. The pump runs at system voltage whenever it is on.

theres no fpr or return line on the fuel rail of a 99.

The 98+ Ranger regulator is inside the tank on the fuel pump assembly. The 98+ Ranger fuel pressure delivered to the rail is regulated to about 65 PSI except for some 3.0 FFVS which are spec'd at a constant 55 PSI.