'92 Chevy Lumina cranks but won't start

This car (my daughter's, age 22) has had SO much done to it- I'm about to give up! Had a rebuilt engine put into it (3.1L) last year, since then many problems. My boyfriend, a mechanic, put new ignition module in it. We have also replaced the Fuel Pump & fuel sensor after discovering very low fuel pressure. The car had a 13V drain (somewhere) and Al discovered Wiring harness to be melted/ welded together in spots after taking off head. After some searching, he found a good wiring harness, got that all put in. Car then started, but would stall right out. We towed it over to Chevy dealer and they tested it and found the Injector ground wire to be crossed, so they fixed that; gave us back Vehicle stating the car 'starts, but runs poorly. Still needs further work to operate safely'.
We have NOT replaced Spark plugs yet, should we proceed with anything else or is this car ready for the junkyard? I'm running out of money! Any ideas would be appreciated. The car starts/cranks but will not turn over/ kick in.