Car has not won't start after replacing fuel pump.

What is your question?

Had not started and did took to mechanic. Said a harmonic balance problem. Got it to start. after turning off for a while, wouldn't start. Replaced fuel pump and fuel filter and it ran from start. Parked it for 4 hours and tried to start, and it just turned over. Is there a fuel relay switch or could it be a computer problem or another possible problem? Or any other advice of things to check?