"Was it a dirty ground at the front fender ground point?"
• Right you are, Jon. The one on the right side. I suspect that battery fumes had their effect over several years, but haven't yet looked at the left side ground to compare the two.

"No one seemed to mention the impulse sensor... I don't think Regina has the same telltale movement of the tach (dropping to zero) as the Bosch setup does."
• The Tach is driven from the Rex ignition's version of the EZK Power Stage, meaning the basic ICU (driven by the CPS/impulse sender) was working.

"Anyhow, glad you found the problem. I'd like to know, as my '92 740 has Regina as well. Like mentioned before, I bet its simple, but overlooked."
• I think most people don't realize how similar the Rex/Regina is to the Bosch EZK/LH 2.4. Same functions, just different components. The 940 greenbook diagrams show both versions, making the comparisons fairly easy.

This stall-out came down to process of elimination:
1) Steady Fuel pump current said the FI was getting "go ahead" pulses from a working ICU.
2) The tach also confirmed the Ignition and Power Stage (but not coil-dist-wires-plugs)
3) Had the Coil, etc. been the cause, I would have expected some sign of fuel soaking when I looked at them between test runs, but they were a nice tan-white with no sooting.
4) That left the Injectors (voltage supply), from the well-known Radio (noise) Suppression Relay/RSR. (An item the 240's are [luckily] missing)
5) A new RSR didn't change anything, and the power to the RSR coil (From FI System relay 87/1) was also common to the Fuel Pump Relay coil and the ECU. Any of those failing would rule out the steady pump current in #1 above.
6) So I went for the RSR relay ground, which looked cruddy but was apparently making an intermittent (and maybe under-hood ambient temp-related) connection that allowed some OK running when warmed up — as on the two good 7-mile runs home from the store.


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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.