backfiring from my 91 regal

i've got a 91 regal custom with a 3.1 engine that will turn but not start and sometimes backfires on attemps. have fuel pressure and new plugs and wires replaced coil and crank sencor map sencor no air leaks so now what ? also changed computer module need help any suggestions will do thanks.:banghead:

Do a compression check to make sure the valves are closing at the proper time. This sounds like a timing issue possibly the timing chain has jumped time and will not allow it to start.

could this also be caused by a bad fuel pump.

car still does not start i don't think timing is off because i was driving when it started to shake like i had bad gas or something.