If your saying it won't even crank, check the starter circuit. Make sure battery has a full charge and connections are good.
If it cranks good but won't start, 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. Some of the national brand auto stores used to loan out a fuel pressure gage, if you don't have one. To visually check for spark at the plugs, pull a spark plug wire loose, use known good plug or spark tester in the boot, ground metal part of plug/tester to metal part of engine, engine cranking, watch for spark.