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You got a doozy here.
As I understand it, the jury rig does basically 2 things:
1) KILLS the FI relay by removing the ground on pin 31
2) runs the pumps via fuse 7 — toggle switch — double Y/R wires pulled from 87a
The result, if the above is correct will be power to the pumps, but NO POWER (from 87b) to:
A) the Lambda Relay, and thus the ECU, and Frequency Valve, plus O2 sensor is ignored
B) Warm Up Reg/Control Pressure Reg heater
This would mean running with no adaptive mixture control (no O2 sensor - F Valve).
The PO may (?) have got it to run like this (in a warm climate) by manual mixture adjustment, but that's just a wild guess.
But when you wire it back normal, with the relay operating and sending voltage out from 87b, you are again powering everything in A and B above, which seems to be conflicting with whatever the PO did to make it run withOUT the A and B stuff.
One more thing — you say "new harness". It's easy to mix up the plugs for the FV and WUR. When you restore normal relay operation, this would drive the FV full open (BLACK SMOKE). FV wire colors should be BN and GN, WUR/CPR wires are BL and SB.
Polarity on the WUR plug matters too. I think there have been posts where harness replacements have had problems here with blowing fuse 7, maybe it could also just cause high current? I don't remember the specifics right now.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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