1995 saturn

I need some help. I bought a used 95 saturn with ablown engine ( original
engine had a blown piston- odometer read(s) 83,000 miles). bought a used
engine and swapped the old out and fthe new in. new engine won't start. gets
spark ( simple ground test used); gets fuel to injector rail ( pulled line
loose ); pistons have compression ( did compression test ). now I admit I am
not a " mechanic" but this is the third car that I changed engines on (
previous- 85 cougar, 98 taurus ) got them to work -thought that this would
be nice project for my teanage son and me. any thoughts where I might look
to find the problem?? what happens is the engine turns but won't start.