1995 Cutlass Supreme Help Please

[1995Cutlass]

I have a 1995 Cutlass supreme 4 door with a 3.1L,3100, that we had a problem with anti-freeze getting mixed in with the oil. So we found a 1994 Chevy Beretta that had a 3100 also. We switched the engines. Both engines ran before we switched them, the cutlass one not so good but still ran. Now that we got them switched we cant get it running. it turns over and starts up for just a second, long enough to hear it start, but it just wont keep running.

We have changed the fuel pump,map sensor,and some gaskets.

Cant figure it out.
any ideas?

[1995Cutlass]

anyone?
could it be the fuel pump?
they both ran so i dont get it.

[thisnametooktolong]

ECM is not getting the hand off to run the ICM

[blaylock916]

All vacuum lines where they need to be? Check that I had a similar problem.

[1995Cutlass]

So i changed the ECM and itstarted a few times, sounded rough, but started. Now it wont start though,only turnover. We have a fuel pressure gauge hooked up to it and it says nothing with only the key on but when you turn it over it goes up to 40 for about 5 seconds than goes back to 0. We also changed the fuel filter. What should i do now?

[1995Cutlass]

Im like 99% sure that all the vaccum lines are connected right.

[maxwedge]

Pinch off the return line, turn the key on see what the pressure holds at, also check for fuel in the vac hose at the press regulator.