I have a 98 Deville (Northstar) that "cranks" quite a bit before starting, after it has been sitting for awhile. However, when it sits all night it starts right up, as well as when sitting for only a

Try turning the key just to on. Listen for the fuel pump to run and quit. try this 2 or 3 times then attempt to start . if this works it may indicate a leak in the fuel system. Hope this helps

Sounds like the starter to me(I assumed you meant won't crank when hot).I have replaced only 1 starter(on my neighbor's Taurus)in the 15 years after quitting the GM dealer tech job 15 years ago.I probably could make a career just changing GM starters and alternators.(I only have Mopars in my driveway!)

It could be a bad or weak fuel pump, bad or loose wires, are there any Check Engine or Service Engine Soon lights staying on your dash?

does it have three second fuel pump run when you turn key to run position/ in between you should let i rest 5 or so seconds then try it again also some of these cadilacs have oil pressure sending unit wich takes the duty of keeping fuel pressure up is fuel pressure lowering as engine quits eg. rev up some in your few seconds of running while the engine is quit momentum keeps it turning for a short time see if you r pressure maintain thru the wind down

it sounds like you need to replace your battery.jumping it to get it started will charge the battery especially if you are driving it around and will hold charge for a bit.but if truck is sitting all night then battery is just draining

The thermostat opens at 196F, but sitting idling, the coolant fans may not turn on til' 125F.

you have bad fuel presure regulator

likely crank shaft sensor ,maybe fuel pump or cam shaft sensor ,ignition module under coil pack,check your codes as your first effort in this,

have you tried changing you distributor and rotor

My 98 Jimmy runs on synthetic oil and starts well after sitting in cold weather. If the weather is the problem, try checking that. If it is warm... sorry no ideas.