89 Escort LX 1.9L CFI -- Fuel delivery is out of wack

The continuing saga of a dear friend's 89 Escort LX 1.9L with Central 
Fuel Injection (it has a throttle body with a single injector)...

I have ruled out spark as the problem. Spark is good.

I caught the fuel injector in the act of not injecting fuel when it 
should, and all the while the coil is firing a healthy spark to all the 
plugs.

I replaced the fuel filter on the off chance that I was having a good 
day and that would solve the problem.

The gods would have none of it. I wasn't having a good day... not as far 
as reviving my dear friend's Escort goes. Many other things went 
surprisingly well. Little things, but very much appreciated.

Wiping the previous slate clean, I offer the following symptoms:

Sometimes the injector will spray gas and sometimes it won't. When the 
injector will not spray gas, there is fuel and pressure in the fuel 
pressure regulator. I confirmed this by unscrewing the fuel pressure 
regulator cover and watching as fuel sprayed out with surprised force 
and duration. Therefore I have taken it into my head that the problem 
must lie with either the injector, a sensor, faulty wiring or the 
computer. I can hear the electric fuel pump doing its thing and the fuel 
pressure regulator seems to be full of pressurized fuel. Whether the 
pressure is up to specs, I don't know, but I was mightily impressed with 
the force with which is sprayed out when I loosened the screws of the 
fuel pressure regulator cover.

Another symptom is that the engine tries to stall immediately after 
starting. I can keep it alive by constantly pumping the gas pedal. No 
one position on the gas pedal will keep the engine running, but pumping 
it will. But that is no way to go through life. At present, the engine 
seems to start consistently but will not run.

I don't have a noid light to check the signal to the injector wiring, 
but since the injector sometimes works I have to assume that the wiring 
sometimes works as well. The Chilton manual suggests that the Throttle 
Position Sensor plays a role in the correct operation of the fuel 
injection system, as does the PCM (Powertrain Control Module, or engine 
computer). I'll give that last one a great big 'DUH'.

The Chilton manual spells out some diagnostic procedures which I will 
endeavor to undertake in the coming days. However, my vast arsenal of 
tools does not include noid lights to check injectors as I am new to 
fuel injection. I may buy some... or I may not. It all depends on 
whether or not I solve the problem without them while I waffle on their 
purchase.

God, I hope to hell, for the sake of future generations, the world 
transits soon to electric vehicles.

-- 

"Forget it, Jake. It's the Internet."