fuel pressure low

[stokesu]

1997 4.0
I'm got about 32 psi

New fuel pump, EGR, fuel pressure sensor, maf, pcv.

I'm still getting to lean codes.

 

[Curious Hound]

Fuel filter? With the engine not running - turn the key to the run position for about 5 seconds. Then turn it off. Then back on. Do that about 3 times. Then check your fuel pressure. Each time you turn the key on, it will run the pump for 2 or 3 seconds. See if that gets the pressure any higher. Not sure if a 97 needs 35psi or more like 50-55psi. It changed somewhere around that time.

If the pressure doesn’t come up that way, then i would think it’s probably the pump or filter.

Otherwise, check pressure with the engine running. If low, maybe fuel pressure regulator which you haven’t mentioned testing or replacing.

 

[stokesu]

Fuel filter? With the engine not running - turn the key to the run position for about 5 seconds. Then turn it off. Then back on. Do that about 3 times. Then check your fuel pressure. Each time you turn the key on, it will run the pump for 2 or 3 seconds. See if that gets the pressure any higher. Not sure if a 97 needs 35psi or more like 50-55psi. It changed somewhere around that time.

If the pressure doesn’t come up that way, then i would think it’s probably the pump or filter.

Otherwise, check pressure with the engine running. If low, maybe fuel pressure regulator which you haven’t mentioned testing or replacing.

I changed that

Fuel filter? With the engine not running - turn the key to the run position for about 5 seconds. Then turn it off. Then back on. Do that about 3 times. Then check your fuel pressure. Each time you turn the key on, it will run the pump for 2 or 3 seconds. See if that gets the pressure any higher. Not sure if a 97 needs 35psi or more like 50-55psi. It changed somewhere around that time.

If the pressure doesn’t come up that way, then i would think it’s probably the pump or filter.

Otherwise, check pressure with the engine running. If low, maybe fuel pressure regulator which you haven’t mentioned testing or replacing.

I changed that all so
Not sure what the correct pressure is to be.

 

[rusty ol ranger]

@adsm08 @RonD

Just because you got a lean code dont mean its a fuel issue. It could be (and probably is) a vacuum leak or possibly a bad O2 sensor.

 

[McWillies]

Specifications​
Engine Displacement (Cubic Inches)	245 CID
Type	OHV (1990 – 2000) (VIN Code X) SOHC (2001 – 2007) (VIN Code E)
Bore x Stroke	3.95 x 3.31 inches
Compression Ratio	9.0:1
Fuel System	Sequential Fuel Injection
Fuel Pressure	39 – 40 PSI (30 PSI @ idle) (OHV Engines) 64 – 75 PSI (SOHC Engines)
Horsepower	160hp @ 4200 RPM (1990 – 2000) 207hp @ 5250 RPM (2001 – 2007)
Torque	220 @ 2400 RPM (1990 – 2000) 238 @ 3000 RPM (2001 – 2007)
Oil Pressure	40 – 60 PSI @ 2000 RPM

Copied straight from the tech library. Sounds like you have solid pressure if the 32PSI is with the engine idling. Lean codes could be a number of different things. I'd start with checking for vacuum leaks, as rusty said.

 

[adsm08]

I agree with Rusty.

97 should be the last year for a return style system. ~35 PSI at idle is spec, but there is some leeway on that number. 32 PSI is not causing lean codes.

I would be looking into things like MAF sensors and air leaks.


If you can, with the engine at temp, get me your long and short fuel trim numbers at idle and also at 2500-3000 RPM. There is some fancy math I can do to tell you which direction to look.

 

[RonD]

Simple test to check for Vacuum leak

Warm up the engine, i.e. drive or idle for at least 10min

Let it idle and open the hood
Unplug the 2 wire connector on IAC Valve, valve will close
Idle RPMs should drop...........to about 500rpms, engine barely running, or engine may even stall, either is GOOD, no vacuum leaks

If idle doesn't change, then you have a vacuum leak

Do you have 1 or 2 Lean codes?
And what are the exact codes, full list here: https://www.therangerstation.com/tech_library/OBD-II_codes.shtml

The code a computer chooses to use is important, but the 900 other codes it does NOT use can also help you eliminate possible causes for that chosen code