1999 GMC Jimmy Starting Problems

Charge up the battery, have a helper crank it while you visually check for spark at the spark plugs. If you have spark everywhere, use a gage and check fuel pressure. Also, check for injector pulse with engine cranking. You may need to check compression as well.

If no injector pulse, check voltage and ground at the injector, check for an rpm signal, comes from crank sensor, check security system where applicable.

Can you check for applicable codes? To check codes, yourself, at the least you need an obd 2 code reader.

Just a thought, if you have the spider fuel system, that system is known for problems.