Welcome to TRS
1992 4.0l uses Batch fire injection, 6 injectors, one for each cylinder, and Ford EEC-IV OBD1 60-wire computer
Throttle body injection just uses 1 to a few injectors, at the throttle plate, and a stand alone non-Ford computer
So if you indeed have throttle body injection you will need to find out what brand and model number of the computer you are using to trouble shoot it
The 50/50 test(spraying fuel in manually) indicates the spark system is working and timed correctly, and compression is good
In a 1992 4.0l Ford used the EDIS-6 module and coil pack, timed by crank sensor
Yes, the fuel pump should run for 2 seconds each time key is turned from off to on
The usually means you are using stock Ford computer, also that the inertia switch is OK, and fuel pump relay
No, there is no other "solenoid" or valve on the stock fuel system
There is a fuel filter that can block flow from tank to engine, in the frame rail under drivers seat area, but would have to be very very clogged up
The "throttle body injection" term is what is throwing me off
Can you elaborate more on that, and are you using the Ranger fuel tank or a custom tank(fuel cell) and pump setup?
That would effect fuel gauge readings