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I'd like to add a few comments here:
1) In the North American and Scandinavian markets at least, a 1990 740 with GLE trim level came with the B234F 16-valve, LH 2.4 fuel injection (ECU) and EZ-116K ignition controller. In some markets the B234F used the Regina ECU and "Rex i" ignition. You say you have a B230F. In that year it would also either have LH 2.4/EZ-116K or Regina/"Rex i" (or Rex-Regina as it's often known). The fact you have an OBD(I) diagnostic socket means it's definitely not LH 2.2.
2) At the OBD socket, the 1-1-1 code in socket 6 means the ignition side is more or less happy -at least the sensor signals are okay. You didn't mention checking for codes at socket 2 for the fuel system ECU.
3) You tested the injectors by directly applying 12 volts. It's better to use the OBD system do that. There's a description of how to run diagnostics using the OBD system here in the 700-900 FAQ OBD Diagnostic Procedures section.
4) Has anyone mentioned a failed/failing crank position (RPM) sensor as a possibility? The original symptoms sure fit -no hot restart leading up to intermittent no starts then no start at all. Check the Crank Position Sensor section of the 700-900 FAQ for more details.
Of course people should be jumping on me for even suggesting that because a) the crank position sensor is connected to the ignition system and b) the OBD socket gave you a 1-1-1 code and not a 2-1-4 code for a bad crank position sensor. The fact that the engine ran when you manually dumped in starting fluid apparently may or may not mean the ignition control side is functional -you need to check for a strong spark at the plugs as mentioned. In any event, in my limited experience, a weak crank position sensor does not always seem to raise the 2-1-4 code. I just went for a replacement sensor based on dry plugs and the no start symptoms and all was well.
I do have a theory how the ignition side can be functioning okay with a weak crank position sensor when the fuel injection side is not. The ignition controller has to pass the crank position sensor signal on to the ECU before the injectors will get pulsed. A weak crank position sensor signal (seemingly the most common form of failure) may be adequate to keep the ignition controller happy, but the signal passed on to the ECU may not be enough to keep it happy. If the ECU is unhappy with the crank position sensor signal, you're supposed to get a 1-3-1 code. As mentioned, I've had bad crank position sensors causing no starts that didn't raise any codes. BTW the 2-1-4 and the 1-3-1 diagnostic codes do not set the Check Engine light (go figure, but then again I suppose checking the engine is a rather obvious thing to do when it won't start).
There is a partial test for the crank position sensor. This is not a definitive test -if the test fails you do have a bad sensor, but if it passes you may still be getting a poor signal, such as when the braided shield is damaged when it rubs against the cooling system return pipe. Disconnect the crank position sensor at the firewall. Then using a DVM, measure resistance between the red and blue wires. You should get 170+/-30 ohms at 20 degC (room temperature). There were also early sensors (with a yellow band on the cable as opposed to the later ones with a white band) found in the 1988 to early-1990 production years (possibly yours). These were known to be weak. The test for the early ones is 240+/-25 ohms. You actually have to check the part numbers on those with the yellow band as there was a small production run of revised yellow banded ones that weren't weak. You should also check that there is continuity (virtually zero ohms) between the sensor black wire and chassis ground (there almost always will be unless the cable is severely damaged).
Because your initial symptoms so closely match that of a failing crank position sensor, I would even go so far as to suggest replacing the sensor on spec before getting too carried away replacing any of the more expensive parts. In particular, for the power stage, which is another prime suspect, it would be nice to have a known good one to swap in for testing before replacing it since new ones are rather pricey.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now
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