Based on the information you provides I will try 2 paths of troubleshooting to get you started at least.

Does engine turns when you turn the ingnition key?

1. If not try to jump start, make sure you let it charge for few minutes before you crank it up. If it fires up, culprit could be one of these: your battery, Alternator, or Your charging circuit. Since you started and ran it for 15 minutes, car sat for overnight and did not started in the morning. You might have slow current drain in your electrical circuit.

2. If it turns but do not fire up, you could have Fuel related or Electrical related problem.
2a. Fuel related, do you have gas comming to injectors? if no it could be blockedfuel filter, empty fuel tank (sorry), FPR or Fuel distributor. If gas is reaching to the injectors move on to next step

2b. Do you have spark in the plugs, take one spark plug out leave the wire connected provide the ground to it, crank the car and look for the white spark in the spark plug electrode. if No spark, it could be one of these; ignition coil, distributor cap, rotor, ignition wires etc.

Please provide more data after doing the above step to further investigate the issue.

If you want a blind shot, I will go for distributor cap and rotor.

I hope it helps, feel free to ask any more questions.
Good luck and keep us posted.

Thanks

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87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)