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If Chuck (porkface) is right, and the "chattering" you heard is from the injectors, then the ECU must have got the "Go Ahead" signal from ICU terminal 1 at the Chrysler CU. Bentley doesn't show it, but that wire from ICU 1 splits and goes to Coil 1 (as a pulsing ground) and also to the ECU pin 1 to get the FI system going (by grounding pump relay 85 blue-green wire, for example).
I think Bentley has the B-C jumper test wrong -- that is, the spark and FI action is triggered when the B-C jumper is removed, simulating an Impulse Sender "vane" leaving a "window" (which is when the timing pulse is initiated), rather than when B and C are connected.
So I'd say to try that B-C test again, looking closely for spark at a plug, and listening for the pump to run briefly (which Bentley doesn't mention), or the Pump relay to click ON for a second, when the jumper is removed.
Speaking of the Pump relay, you might try back-probing the Blue-Green wire at terminal 85. With the key ON, that point should be show +12v (reading thru the coil from 86 (IF fuse 13 is good). Then, when the B-C jumper is removed, that 85 relay terminal should go briefly from +12V to 0V (ground) when the ECU reacts to the B-C jumper removal.
I don't usually have much good to say for Haynes vs Bentley — but Haynes pages 4A-27 (fuel) and 5-7 (ignition) might be helpful here, showing how ICU pin 1 relates to the Coil 1 and FI ECU pin 1 for example.
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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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