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Look on the intake and find the fuel injectors, they are connected to whats called the Fuel rail, it supplies them with fuel
The fuel rail will have a test port on it, usually on passenger side of a V6
Test port "looks like" the air valve on a tire, because that is what it is, a Schrader Valve, it may even have a cap on it like a tires air valve, unscrew it, nothing will come out, same as tires cap
You screw on a fuel pressure tester and that presses the center pin in so you can read pressure in the fuel rail
Fuel injected Engines running pressure for 1985 to 1997 Ranger is 30-35psi
Also on the fuel rail is the Fuel Pressure Regulator(FPR)
FPR has the RETURN fuel line and a Vacuum hose attached
With engine running you want to unplug that vacuum line, and make sure no gasoline comes out, lol, and also see if fuel pressure goes up to about 43psi
Put vacuum hose back on
Pressure should drop back to 30-35psi
Shut engine off key off
Watch if fuel pressure drops, it should go down to 20-25psi and stay there, basically for a year or two, long time
If pressure drops to 0psi then either the check valve inside the fuel pump is leaking, or the FPR is leaking
Or a fuel injector is leaking but.................engine would run poorly and MPG would be about 5mpg, lol
If pressure is 0psi, cycle key on and off 1 time, should see about 10psi, cycle key again and should see 20psi, ect...it will top out at 43psi or whatever FPR showed with engine running and no vacuum line attached
The fuel pump only runs for 2 seconds with key on, that's a safety feature, so you have to cycle the key on then off repeatedly to build up pressure again if its leaking down to 0psi with engine off
1998 and up Rangers use 55-60psi fuel pressure and no RETURN line, FPR is inside the gas tank with fuel pump