94 ranger keeps stalling
 

My ranger will start but only stay running for 30-60 seconds then stall out. Can any tell me how to systsystematically diagnose this problem

Under the truck in the frame rail(drivers seat area), is the fuel filter, $10 part, if you have noticed a drop in power at highway speeds recently then filter was probably getting full of debris, and now is completely clogged.
A filter rarely clogs "overnight", there would be warning signs.

And speaking of warning signs, have there been any?
Or has any recent work been done on the vehicle?
Did you just come out one morning and it had this 30-60 second issue, or did it happen first when engine was warm?

On the fuel rail passenger side top front of the engine you will see the Fuel Pressure Regulator(FPR), it is connected to the fuel rail and has a fuel line connected to it and a vacuum line, remove this vacuum line and see if there is fuel in it, there shouldn't be, if there is replace FPR
If there is no fuel seen or smelled, leave vacuum disconnected and try to start engine.
If engine stays running the FPR is probably bad, stuck wide open so fuel system can't build any pressure.

Ford only primes the fuel system for 2 seconds when key is first turned on.
So when you turn the key on listen for the fuel pump, it is loud enough to hear in the cab.
Now turn key off and then on again, repeat this 2 more times.
What you are doing is building pressure in the fuel system, it should be 35-40psi, you can't over-pressurize the system.
Now try to start engine and see how long it will run, if it runs for a few minutes and then dies the check valve in the fuel pump is most likely issue.

You can rent a fuel pressure gauge and test fuel pressure.

I assume opening the throttle a little when engine does start doesn't keep it running, but can you get the RPMs up by doing that?

I disconnected the vacuum line from pressure regulator n no gas. I also replaced the filter. When i did a pressure test i had to turn the key on n off 3 x's to get pressure up to 35, but it would then rapidly go all the way back down. It will only start for 15-20 seconds but during that time the pressure stays at steady 35psi then spikes to 40 briefly right as it stalls. I did forget to try to start with vacuum line off though. The only symptoms i had a week or so before i broke down was it wouls seem to hesitate kind of surge when going over 75. The only work i did recently was change a blown upper radiator hose. I drove it 60 hyway miles to work n on the way home it started sputtering, then ran okay for a couple minutes then it wouldnt accelerate over 40 and began sputtering real bad...wouldnt stay running after that n towed it home

Fuel pressure should hold for a few months.

There are 4 ways to lose pressure
1. leak in the fuel lines, you would small gas odor
2. leaking fuel injector, you would notice extra smoke out tail pipe, very HOT cat converter, very low MPG
3. bad FPR(fuel pressure regulator), it has a spring inside that holds it closed, keeping system pressurized, the vacuum line sucks the spring(valve) open when engine is running, extra fuel is sent back to tank in the return line.
If you remove the return line from the FPR and turn on the key(not the engine!), no fuel should come out of the FPR as the valve should be closed, if fuel comes out, then thats the pressure leak, replace FPR.
4. fuel pump check valve(backflow preventer valve), this is part of the fuel pump inside the tank, it prevent loss of pressure when pump is off.
After eliminating 1., 2. and 3. as the leak point this will need to be changed.