07 ranger3.0 125k. Bought used from a dealership that just got it from an auction.
triying to fix an intermittent misfire at idle.. fuel trims show im running lean.. connected a fuel pressure gague. Someone has been there before. The cap for the valve on the fuel rail is cross threaded and the metal clip that holds on the fuel line is bent.
pressure at 10 psi. Engine off.. Cycled key once came up to 45. Started it came up to 65psi. It lost 10 lbs of pressure in a couple of minutes engine off again.
​​​​​it always starts easily..
question: is this a tired fuel pump causing the misfire? Or just a leaking check valve?

 

No, probably not, running pressure should be 55-60psi, 65 is fine
Raise RPMs to approx. 2,500 and hold there while watching pressure, if its slowly dropping change fuel filter FIRST
Retest, if its still dropping change pump

The drop in pressure key off is only an issue with start up, and if one key turn(off to on) gets above 30psi then it will start no problem, as far as fuel is concerned

Lean codes are CAUSED by mis-fires, they usually don't cause mis-fires unless it mis-fires ONLY at highway speeds

Lean codes don't mean you are "running" Lean
Lean code means computers calculated open time for the fuel injectors was no long engine, Fuel Trims are + and -
0 fuel trim is computers calculated Open Time, +2 fuel trim means computer is opening injectors 2% longer than calculated to get a "good burn" as measured by O2 sensor on that side of the engine
-2 fuel trim means computer is close the injectors 2% sooner than calculated

+15 will set Lean codes
-15 will set Rich codes

So engine was never running Lean, computer is adding extra fuel as needed, the Codes are to tell driver/owner that there is a problem because calculations are off by more than 15%