Toyota Repair: 89 pickup 3.0 V6 starts for 4 sec then dies, fuel pressure regulator, haynes book

Question
Hello Ted;
I hope you find this interesting.
My son purchased a 1989 pickup, cheap cause it did not run. It has the 3.0, V6 with EFI. The original trouble codes in the truck when we got it was 24, 32 and 51. After resetting the computer, we only get the 51. The others may of come because I tried to run the truck with the intake disconnected. I later learned the truck will not run with the intake disconnected or any leaks in the intake or that matter. When you go to start the truck, it will run for about 4 seconds then quit. Try again and it will run for 2 seconds then sometimes not start at all after that. Wait awhile and it starts all over again, meaning it will run for the 4 seconds - quit and so on.
Each time I crack open the main banjo fitting near the fuel pressure regulator, gas (under pressure) comes out. Not much but it does come out.
If you feed starter fluid into the throttle body, it will continue to run. Therefore, we know it is not a spark problem. We checked the fuel pressure using two gauges directly into the fuel line before the filter and we get 42 PSI and the pressure holds. We changed the fuel filter with no change to the problem. I don't have a banjo adapter to be able to check the pressure at the fuel rail.
I checked, according to the haynes book, all the ohm meter checks one could do. ie; coil, relays, injectors (the ones I can get to) distributor, air meter, etc. The igniter (next to the coil) has been changed by the previous owner. The main relay (under the hood) appears OK and the circuit opening relay (in the kick panel) appears to be working properly.
Within one of your answers to someone else having this similar problem with a 91 4X4, you suggested jumping FP and E1 in the diagnostic connector next to the fuse panel under the hood. I did that before looking at the schematic in the book. Yes, we blew the EFI fuse. Maybe you meant to state E1 to Fc. But Fc is not in the diagnostic connector in our truck. Don't know about a 91.
After looking at the wiring diagram, I can see why. Fp is the 12Volts feeding the Fuel pump. I then shorted pins 4 (E1)and 5 (Fc) at the circuit opening relay which appears to bypass the Air metering system (like shorting pins 1 and 2 as in closing the switch) and it still did not help. I believe this would give it the hold current circuit to keep the circuit opening relay closed giving ground to the grounded side of the secondary coil in the relay. (That bit comes from my old electronics training)
Also, I started checking readings at that diagnostic connector and read 12V at B when key on, which makes sense and then 12V at Fp only when engine is cranking and running but drops to 0V when engines does come to a complete stop. I can also hear the click inside the air meter box at the same time. This tells me the holding circuit for the fuel pump is turned off which seems normal when engines stops.
I think the injectors are not working and can't figure out what circuit is telling them to stop working. We have a friend with a $5000 snap-on diagnostic system that I am hoping can connect to this diagnostic port and help us figure this out. I just ordered a new ECU from eBay, should have that in a few days. From what I've researched the airmeter can cause this by shutting off the fuel injectors if the reading is incorrect, and the distributor can also be a problem if its not reading the correct RPM. However, I would rather not go buying all of these expensive items unless I have a better idea of what I'm dealing with. I was also considering the TPS.
Are these engines and systems that sensitive that if there is the slightest problem in the intake, it will not run?
Any suggestions are welcome.
Frustrated Dad

Answer
The air flow meter can not turn off the fuel injectors but it controls the fuel pump to be either on or off, the injectors are controlled by the ECU, the ECU needs to see a couple of input signals or the injectors won't be turned on, these are the IGF and the NE signals, the IGF is the signal that tells the computer that there is spark to the spark plugs(which seems to be the case) the NE signal is an rpm input signal that lets the computer know the engine is turning over, if this signal is not there the injectors will not fire, there is a simple little test light available at most autoparts stores that plugs directly into the injector connector, it will flash if the computer is commanding the injector to turn on/off, if this does not happen the problem may be a loss of the NE signal or a bad ecu or a bad ecu ground or wire problem, there should be a steady voltage to one side of the injector connector, between 6-12 volts depending on whether an injector resistor is used, the other side of the injector connector is the on/off ground signal controlled by the computer which cycles the injector "ON" time according to engine demands.