Would be happy to share what little I know, but this is going to be a rather long post, so prop your eyelids open.
First, Steve Wood's website
Vortex Buicks is a valuable resource for troubleshooting. The Turbo Regal website
Turbo Regal Web Site also has a troubleshooting section. I used the Steve Wood site, because the information was grouped better to my liking.
After following the no start flowchart step by step, indications were that the ignition module was probably at fault. But, the coil pack could have been a problem, also, since the injectors would fire, but no spark. Either the module or the coil pack or
both could be bad.
I determined that injectors were working by pulling off one of the electrical connectors, and checking for voltage across the connector terminals with an
analog vom on low voltage range while cranking engine. If ok, you can see a blip on the meter needle when the the voltage pulses. There will be no movement if there is no pulse. A digital meter is not fast enough to register a pulse. You can also use a Noid test lamp instead of a vom. I wouldn't try to use a regular 12v bulb, since the filaments probably would not light with such a short pulse. Being cheap and having a vom handy, I used it instead of paying for a Noid kit. Afterward, pulling a spark plug and observing that it was wet with gas helped verify operation.
To eliminate one possibility, I removed the coil pack from the ignition module and tested the coil pack with a digital volt meter (analog vom would also work). Check secondary (top post terminals) by measuring resistance across 1-4, 2-5, and 3-6 packs. From what I've gleened from web search, secondary should be about 12K ohms or so on this car. Mine was in very close range, except for the 2-5 pack, which measured about 25% higher at 15K ohms. That should still be useable and fire the plugs, even though the spark might be a little weaker on that pack.
Next, I checked the corresponding primaries on the bottom side of the pack which should be less than one ohm each. Mine was .9 ohm across each, well within range.
An open across any of the above measurements means the coil is unuseable. Throw in the trash. This is a cheap, quick and dirty test, but I felt all coil packs were alright.
All fuses were good, so was probably some internal fault of the module.
The ignition module was filled with sticky goo which was probably the dialectric which melted after an overheat condition after failing. I'm just guessing here. But what a mess! I cleaned off the spade terminals and took the module to O'Reilly's who have a coil/module tester which performs five or six different tests. My module could not even start the first test.
The store had a BWD brand module in stock. It is made in U.S.A., but that really doesn't mean much anymore. They put it on the machine, and all tests ran successfully. They let it cycle three times and it passed each test each time.
I took it home, slapped the coil and module together (be careful to get the spade connectors in the right places), and buttoned up everything. Turned the key.....fired right up. Muy bueno.
Have heard that some aftermarket modules can malfunction and set a code 42. To check for this, I shorted the ALDL connector A and B terminals with a paper clip and looked for any set codes while the SES dash light did its semaphore signaling. The only code was 12, which repeated itself continuously, indicating normal operation.
I'm not trying to be condescending here, but I'm assuming the reader knows the difference in voltage, current, and resistance. Be careful which function is dialed in on the vom or dvm, i.e. don't try to read voltage on the resistance scale, or vice versa.
That's all there is. Hopefully it will run tomorrow, although who knows with these old cars?