1995 Cadillac Fleetwood black smoke and now won't start

Hello all,
I have a 1995 Cadillac Fleetwood with only 87000 miles. I have owned for the last 50000 miles. My land yacht will not start. It cranks and catches occasionally but will not completely fire up. This problem began right after it sat for 3 weeks. When I started it, it ran but sputtered and then belched black smoke out both tailpipes before dieing.

I have replaced the fuel pressure regulator since it seemed to have been getting too much fuel. That did not help.

I am at a loss since the OBD shows no codes. Any ideas would be appreciated.

Quick diagnosis is to listen for the fuel pump to come on when you turn the key to on. If not you have a fuel problem-pump, relay, fuse, computer. If it does come on, then you’ll need to check for spark with a spark tester.

It does seem like it could be a fuel system problem. What kind of fuel system does it use? Electronic port injection? Throttle body injection? Carb?

Black smoke could also be caused by sticking or broken piston rings too. Likewise, valve stem seals.

Take a look at the tailpipe. Is it greasy, oily? Or more like soot? Or nothing unusual at the tailpipe?
Might be worth it to pull a plug too, see what the working part looks like. Might be oil or carbon fouled.