92 grand am hard to start, backfires

[ta4168]

my son changed the engine in his 92 se sohc. its all together now but hard to start, and backfires through the exhaust when trying.

no codes, no check engine light.

we are getting spark, and there is fuel in the fuel rail. there is no schrader valve on the rail to test pressure, and i dont know how to test it.

i am suspecting a fuel delivery issue. we did change a plugged fuel filter.

anyone know how to test the regulator? how do i test the fuel pressure? any ideas?

[3100]

on 92 3.3 I you have to remove upper plenum and you will see test port on the fuel rail. specs are: 40 to 47 psi engine off key on.

pressure regulator if bad will leak fuel into vacuum line (check vacuum line for fuel)