fuel pressure test port and fpr where are these

[romoore]

Trying to find fuel pressure test port and FPR on 2005 ranger, 4WD, 4.0 Engine, cannot see them anywhere, please help.

Ron Moore

 

[RonD]

Welcome to TRS

1998 and up Rangers use a Returnless fuel system, so no FPR(fuel pressure regulator)

2005 Ranger 4.0l SOHC may or may not have a fuel pressure test port

Test port is a Schrader valve(same as tire's air valve) it will be on the fuel rail between fuel injectors, it comes from factory with a cap screwed on to it, like tire's air valve cap.
Cap doesn't hold pressure, same as tire's cap, just there to keep dirt out.

1998 and up Rangers ran 60psi fuel pressure, 1997 and earlier 35psi
Fuel pressure should hold above 45psi key off, for a few MONTHS

If you have a hard start
Cycle key on and off 3 times, this Primes the fuel system 3 times, generating approx. 15psi fuel pressure each time
Then try to start
If it starts right up then loss of fuel pressure, key off, is indicated

This is usually caused by Check Valve built into the fuel pump leaking fuel back into tank when pump is off


Stalling out, "running out of gas", at higher speeds usually means fuel filter needs changing or fuel pump is starting to fail

 

[romoore]

missing ob cylinder #3 at about 2700 rpm

Have a miss at about 2700 RPM on cylinder #3, new coil, wires plugs, TPS, IAC Clean MAF new EGR valve too and fuel filter. Sets a 303 code only.

Ron

 

[adsm08]

The fuel filter is the fuel pressure regulator on the mechanical returnless systems. Basically when enough pressure builds in the forward part of the system the excess fuel begins returning to the tank from the 3rd (smaller rear-facing) port of the fuel filter.

Not all 4.0 SOHC engines had a fuel pressure test port. The ones that did usually had it in the front of one of the two rails.

However, fuel pressure would not cause a misfire on a single cylinder. A lousy injector might though.

 

[RonD]

Is the misfire only under load or can you feel it when REVing engine in driveway?

Yes, swapping injectors #1 and #3 to see if misfire moves to #1 would be a way to find out if it was an injector issue

 

[romoore]

misfire

The #3 cylinder misfires under load only. does fine setting in driveway and reved up.

 

[RonD]

3 things are needed for cylinder to fire
1. fuel, in the right mix with air
2. spark, at the right time and strength
3. compression, above 120psi

Compression will be taken off the table, for now

Fuel pressure, as adsm08 said, would tend to effect more than one cylinder
Fuel mix from partially clogged injector could effect under load operation only
But I would expect higher speed highway driving, light load flat ground, to also be effected.

Spark, when accelerating fuel mix goes very RICH, so spark needs to be strong or it can't ignite the mix.
Each coil in coil pack sparks 2 cylinders at the same time, while it would be possible for only 1 cylinder to be effected it is a long shot.
I would first switch spark plug wires on #2 and #3, or any similar length wires, see if issue moves to the "other" cylinder
Next pull out #3 spark plug, check it's gap, 0.054 is a big gap and 4.0l needs it to get a good strong spark, if you can replace it with 1 new spark plug, or swap it with #2 or easier to get to spark plug.

If spark doesn't seem to be the issue then you will need to move on to #3 fuel injector

Coil pack wiring
3 4
2 6
1 5
front

The 5 6 4 side gets me

 

[adsm08]

Swapping plug wires from 3 to 4 would be the better test. Try to keep paired cylinders together so that you don't cause a miss from timing being off. One side of the coil failing and causing a miss on only one cylinder is far from a long shot. It is actually a common occurrence.

Fuel injector plugging happens on the 4.0 SOHC as well, but due to the way the rail is designed it usually happens to injectors 1 and 4.

 

[romoore]

New coil , wires and plugs but I will try it and see what happens, I have seen defective parts out of the box.