Low fuel pressure!!!

[9miller]

Hello all, I have been coming to this forum since I got my ranger in November and you guys have some great information, has helped me many times!
Now I am having a problem I can't find an answer for, my fuel pressure is at 12-14 psi at idle and running really rough.
KOEO is at 22 psi.
remove vacuum line on FPR and it jumps 8-10 psi At idle.
haynes book says 35-45 psi KOEO, 25-35 KOER.
Voltage to pump is 13.7v, ground ohms at 3.5 to frame.
changed out the filter, FPR, and the pump, had no changE to pressure. Just for the hell of it I replaced it all again since the pump and FPR were under warranty, both times I did the whole pump assembly.
I am not sure what else I can do, there is no leak as far as I can tell. What else could be effecting my fuel pressure?
this is on a 96 2.3l 5 speed. Any help at all is greatly appreciated.

9miller

 

[9miller]

Is this in the correct sub forum admin?

 

[RonD]

Fuel pressure should be 35psi for your model year.

Fuel flow is created by the pump, fuel pressure is created by check valve in pump, FPR, and fuel injectors.

Obviously you don't have a fuel line leak or you would smell the gasoline fumes?

And since you replaced the fuel pump assembly the in tank fuel lines would have been replaced as well?

New FPR should work, but "new" now-a-days means "never tested", it no longer means "it works", lol.

So all you have left is fuel injectors.............

This is assuming your fuel pressure gauge is accurate?

Install gauge on fuel rail
Turn key on count to 3 and turn it off
Repeat this 2 more times
You are Priming the fuel system 3 times
Check pressure and watch the gauge, it should be holding above 25psi, if it continues to drop you have a leak in the system, as you surmised.

There is a test for leaking injectors using Clear Flooded Engine routine
After Priming the system 3 times again
Leave Key on
Press gas pedal to the floor and hold it down (this is Clear Flooded Engine routine)
Computer will now shut off fuel injectors
Try to start engine
It should just crank and NOT fire at all, it has spark but no fuel
If it fires, even a little, then fuel is getting in from some where, maybe a leaking injector

You can ID the injector using the above test.
Unhook spark plug wires on BOTH coils for #1 cylinder
Repeat above test, if engine still Fires then hook #1 wires up and unhook #2 wires, repeat for all 4 cylinders, when engine doesn't Fire thats the cylinder with leaking injector

 

[9miller]

RonD,
I tried what you said about testing the injectors, after priming 3 times and while holding down the throttle it cranked for 3 seconds then fired up, so I imagine I have a bad injector, just have to ID it now.
however, wouldn't a leaking injector cause a rich code? I get an intermittent lean code about every week or so. P0171

 

[9miller]

Okay, just went to ID them and it was the first cylinder. Guess I can replace intake gaskets while I'm there since I'm not sure of their condition.

A quick question, I'm gonna order from rock auto, and I'm not sure what I should do, I could either;
1. Buy a remanufactured injector for 30 bucks.
2. Buy all 4 injectors as remanufactured for 120 bucks, or
3. Buy one motorcraft injector for 65 bucks.

which would be the most beneficial in your eyes?

9miller

 

[RonD]

Just get a rebuilt.
Did you test the other cylinders just to make sure?
Its important, you could have a different issue.

OK, here is the skinny about fuel codes.
Lean code doesn't mean engine is running lean
Rich code doesn't mean engine is running rich

LOL, confused?

First, O2 sensors can't see fuel, they see Oxygen, hence the name
When O2 see's a higher level of oxygen in the exhaust computer reads that as Lean, to little oxygen and computer sees that as rich.
So nothing at all to do with fuel, just oxygen levels.

If a cylinder misfires what happens?
Nothing, no fuel is burned and more important, no oxygen is consumed(burned with fuel), so all that oxygen is dumped into the exhaust........................
And O2 sensor sees oxygen so...............computer sees Lean.

So computer adds a bit more fuel, and if you already had a leaky injector it could cause more misfires, so more oxygen in the exhaust, ect...................

The computer reads the MAF(mass air flow) sensor to get the air volume coming in, it then calculates the fuel to be added to this air volume based on the 14:1 Air:Fuel ratio, this calculated amount of fuel is "0" for the fuel trim routine.
A "+" number is added fuel, a "-" is less fuel(this is the dwell time, pulse width, of the fuel injectors, + means injector is open longer, - it is open less time).
When driving the computer tries to keep fuel trim between -5 and +5, at idle it will be +3 to +7, idle is richer.

When computer has to add or reduce fuel and it gets to -20 or +20 it will set a Rich code(-20), or a lean code(+20), the engine is never running rich or lean, computer is reducing or adding fuel, the code is to warning the driver than the calculation is off.
This could be from a bad MAF sensor, a vacuum leak, low fuel pressure, or misfires, also other things, lol.

So your Lean code could be caused because of misfires from a leaking injector, or you may also have a vacuum leak, but the lean code means the computer thinks it is adding more fuel than it should based on the 14:1 ratio

 

[9miller]

Well, just tried the test again and it fired up every time when I alternated all four cylinders with the clear flooded engine technique. Now I'm at a complete loss again.

 

[RonD]

Well you may not be getting into Clear Flooded Engine mode.

If possible have someone press down on the gas pedal all the way(or put a weight on it), then see if you can open the throttle manually a bit more, you could have a stretched throttle cable so you don't get Full Throttle.

The TPS(throttle position sensor) gets 5volts from computer, TPS is a variable resistor, like a light dimmer or volume control.
When throttle is closed TPS send computer .6-.9volts(under 1 volt)
When throttle is wide open TPS sends computer 4.5volts or higher.

0 RPMs and 4.5volts or higher from TPS is the trigger for computer to enter Clear Flooded Engine mode and shut off injectors

 

[9miller]

Okay, that makes sense. I'll have to give it another go around tomorrow when it's light outside. If another person doesn't do it I can put the voltmeter on it as well.
thanks again RonD, it's very much appreciated.

9miller

 

[RonD]

You are welcome

Top wire is 5 volts from computer(key on)
Center wire is voltage back to computer, I use a sewing needle to pierce wires and read voltage.

But this won't tell you if throttle cable is stretched