Okay so ive been fishing a stall no start issue for the last few days thats getting worse IF and i mean IF i can get it started it seems to run well and at any given point will just cut out. tach drops straight to zero. I sometimes can get spark out of the coil but it normally doesnt last long. Fuel pump is kicking on that 1-2 seonds when key is turned and i can hear the relay clicking on and off during the start cycle.
i have replaced the following parts

Cap, Rotor, Wires, Plugs
Coil Pack
IAC
MAP
RPM Sensor
ALL the relays in the center dash.
both relays on the reservoir.

Im lost and cant give the wife her car back until im sure its fixed.

I'll throw out the ingniton switch as this happened on my 93 a year or so back. Wouldn't start, then would start, etc. Seems like you have replaced everything else. Also, make sure vacuum line to MAP sensor is good, there is a rubber piece at the sensor that can fail and leak (probably not a start issue). Mike

"i have replaced ... both relays on the reservoir."

Not being familiar with relay locations on the '91 Regina, I'm guessing those relays on the reservoir are the Fan control and the RSRelay. The RSR controls voltage to the injectors, and except for the "tach drops straight to zero" part, your symptoms are quite a bit like my 940 in 2009. [See Geezer Stumped post... RSR Coil Ground Fault]

Since you've replaced so many parts, here's something quick, cheap, and fairly easy to try.

1) Locate the RSR (4 wires, the 2 larger ones are RED and RED-GREEN)

2) Bypass the RSR by inserting a jumper in place of the 2 larger wires (R and R-GR) in the relay harness connector plug.

3) Drive it and see if that helps. NOTE: You can leave the jumper in place. There will no voltage to it with the Key Off. The coil +12v comes from the Fuel Pump relay and the ground side is ECU-controlled.

If you still get the problem, remove and scrape clean the 2 grounds on fuel injector brackets (Brown wire on front, Black wire on rear). The Black one can definitely affect ignition. Not sure about he Brown one.


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

I have experienced the same flakey issues on my 1992 Rex/Regina 745.
I ran auxiliary ground wires from battery negative to every ground point under the hood - including to the two grounds on the intake manifold.
I replaced the coil pack first with a used one, then with a new one. The new coil pack solved a variety of issues.
Have you replaced the high voltage lead between the coil and the distributor? It is very long an susceptible to damage. I carry a space at all times.
Have you checked for spark by disconnecting this long wire from the distributor and hold it near the engine block while someone cranks the car? If you get a spark, the coil is working. No spark, your problem is elsewhere. Funny, I had a coil pack that refused to work until I did that grounding trick. Then it fired up fine. Repeat every morning until I replaced it.
The two plugs that connect to the coil on the drivers side street column sometimes corrode inside. The white one, three leads is on top. The black one, two leads is on the bottom. I have sprayed both with contact cleaner. That helped with a no-spark condition.