Pontiac gran am 2.4 quad 4-won't start

My 2.4 quad 4 engine cranks, but won't run. Engine is getting fuel and fire. When trying to start -the engine cranks, then will run for about 2-3 seconds, then backfires slightly and sputters dead. Compression was checked in all cylinders and read 150psi. Timming cover was removed, and the timming was checked & all timming marks are lined up. Engine sounds healthy when it cranks.I bought this car with this problem, thinking that it may be only a loose timming chain-but that's not the case. Any input would be appreciated.