I have a 2000 Ford ranger 2.4 i4 that only run if I add starting fluid to the engine but then dies.

I replaced the whole fuel pump assembly three different times ,the fuel filter, battery, and the fuel pressure sensor. I have checked the inertia switch and it seem to be working correctly. I also swapped the fuel pump relay with the horn relay as well as changed the fuel pump fuses.

I get electricity to the fuel pump because I checked with a light test but don’t know the exact voltage getting to the fuel pump.

What else could I do or fix!!!!!!

 

Welcome to the forum

Fuel pump will show Battery voltage(12.3 to 12.8volts) for 2 SECONDS when key is first turned on, then after that 5 to 8volts, but NO AMPS, so not fuel pump power, thats computers "monitor circuit"
So the test is just for first 2 seconds, you can repeat key off and then on again as much as you want
So if you see key on 5-8volts on fuel pump wire at the tank then wire is OK
You can also test this at inertia switch, should show the key on 5-8volts on BOTH terminals, this means its passing voltage

The fuel pump WILL get full time voltage when engine RPMs go above 400(engine started), cranking speed is 200rpms
So when you start the engine by adding fuel manually to the intake, RPMs will go above 400 so the fuel pump should start to work full time

2000 Ranger with 2.5l I4 won't have PATS, so thats not the issue
There is a fuel pump fuse in engine bay fuse box, you didn't mention that
There is no fuel pressure sensor????

Battery(12v)------fuel pump fuse---------fuel pump relay----------------inertia switch------------------------------------------------fuel pump------ground

There should be 4 wires on the fuel pump assembly
Pink/black stripe wire should be 12volt from inertia switch(5-8volt after 2 seconds)
Black wire, fuel pump Ground

Yellow/white wire, to fuel gauge in dash
Black/orange wire, fuel gauge(sender) Ground

Make sure the grounds are OK, there is no 12volts unless there is 0volts(battery ground/negative)

There should be a fuel pressure test port on the engine, passenger side on the fuel rail, where injectors are connected, looks like a tires air valve, because that is what it is, a schrader valve
And it works the same way, if it has a cap on it unscrew it, you will see a pin inside just like a tires air valve, CAREFULLY press in the pin, there should be 40+ PSI in the fuel rail if pump was working, so fuel can spray a long ways, BE CAREFUL
Release the pin fuel will stop, same as letting air out of a tire

There can be an EVAP air pressure sensor on the gas tank, no connection to fuel system, its an emissions system part