92 RS 305TBI. I was driving and my car just shut off immed, no sputtering. It would not start. I waited 5 min and it started right up and ran fine. Later on it did it again. Code 53 and 54. This time it would not start at all. Came back next day and it started right up and ran normal. Drove 2 blocks and it started sputtering gave it gas and it stayed on somewhat. started it again a few days later and it ran great left it at idle for 5 min and then it died suddenly. It has had a bad Oil pressure sending unit for years. It has a new ecm, fuel pump, tank and Fuel Tank electronics. I was thinking it could be the fuel pump relay, or have something to do with that sending unit.

 

It sounds like you need to check the alternator output and fuel pump relay/circuit.

 

brand new alternator.