1988 Cadillac Seville 4.5 engine

If it has fuel and spark then check compression these 4.5 motors were junk and have a lot of head gasket problems among other things.

If you go to the site here it will tell you how to test the ignition system under either tune up or how to repair. if the check engine light is on cross A&B on the aldl with a paper clip turn key on and watch light it will blink in 3's 1 then 2=12 which is normal for car off with key on. then look under obd 1 on site on what to check if codes. It may be an ignition module or pick up coil which are in dist an dist must come out to fix pickup coil. I forget what ohms it should have but sometimes wires break due to advancing on an doff all the time. The aldl is below dash left hand side by steering column

https://www.2carpros.com/articles/how-to-test-an-ignition-system

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method