What engine do you have in your 300se is it the M103 ? i think it might be your fuel pump relay this is only for the M103 if you have m104 engine this will noy apply .First remove the FRP relay and on the base of the relay you will see a number by each pin . Get some wire and link 7 and 8 togetherthen put the relay back in place . Try to start yur car. And if it starts and runs without stoping then you fpr is shot .Important that you remove the wire link you have put on the wire 7 and 8 right after .Reason fuel pumps will not turn off, and then fuel will enter the engine none stop,, this will can damage to the engine so do remove it after your check is finished.