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.