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Hi Dave,
Welcome back. First a couple of comments on your post... Then some guesswork...
"The harness has three ground points that connect to the intake manifold"
Slightly puzzling, as the Bentley shows only two manifold ground points for the '86 (3 for '87 on). Not a big deal, I suppose. Wish I had an '86 here to compare to.
"I substituted the missing ECU ground with the free end of a grounded wire placed into the back of the relay harness plug at 86/2 so it makes contact with the Blue/Green wire terminal.The fuel relay closed, the fuel pumps ran when the key was turned on..."
Did you try starting at that point? For now I must assume that you did try—but still a no-start, right?
Try starting again, as above (if you still have some battery life) then check for unburned fuel on the plugs, to see if the ECU is firing the injectors or not. You can hear them click too, using something like a thin screwdriver as a stethoscope between your ear and an injector.
A - If no fuel is getting to the plugs, even with ECU Fuel relay ground forced by a ground jumper, and pumps running while cranking, then we will assume there is still a fuel-related problem. Possibly ECU.
B - However, if fuel is (now) reaching the plugs, but still no start, the question is "Why isn't that fuel being fired? When it did fire the starting fluid?
Some guesses—
1) The spark is there, but weak? Put meter on Coil terminal #15 (verify terminal 15) two Blue wires, check voltage when cranking. How much does it drop below 12V? (or whatever battery shows with no load).
If it drops much below 9 or 10 volts, run a jumper from Battery positive to Coil 15 and check again while cranking. If not significantly better, get battery charged and try again. Remember to remove jumper wire.
2) Basic timing may be off. I think the more volitile starting fluid might tolerate this—and/or a weak spark— and fire sporadically.
• Rotate Crankshaft to 0°, #1 TDC using 15/16" socket on pulley bolt. Crank pulley/harmonic balancer 0° grooves on pulley edges must align with the 0° vertical reference mark about an inch long on the lower timing belt cover.
• The Camshaft should also have its 0° references lined up at this time.. I think your b230 has a notch in back edge of drive sprocket that should align with a mark molded into the rear timing belt cover (remove phillips head screw to check). My 940 b230 lacks this easy-to-see mark, so I'm guessing here.
• The Distributor rotor (centerline) should now be about 5/16" past (CW rotation) the 0° reference notch for #1 cylinder in the outer edge of the dist body. To see the notch, remove the rotor, then the plastic dust shield, then replace the rotor for reference to the notch. The rotor should be be past the notch, if the base timing has previously been set correctly to the nominal 12°±2° advance.
So with your car's unknown history, it's back to basics — Fuel to the cylinders, and a good spark — at the right time.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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