Nissan Repair: engine wont run, oil pressure switch, engine oil pressure

Question
My son has a 2000 Nissan Sentra that was involved in a front end accident and sat for several months afterward. Now when he tries to start it, it will start, but then dies within a few seconds.
I have checked to see that the camshaft is turning; it is. I have checked to see that the fuel pump is working; it is and delivering more than enough fuel with the ignition switch on but the engine not running. When the switch is turned on, the fuel pump only runs for a couple of seconds, then shuts down. Since it just will not run after it starts, what is wrong? I do not have any equipment capable of reading error codes, therefore I do not have any information as to what they may be, if any. The car will not run long enough to get it to a place where I can have the codes checked.

Thanks for any help or suggestions you can give.

Answer
Eddie,

Nissan uses an engine oil pressure switch to control the fuel pump.  After the car starts the computer monitors the oil pressure to keep it on.  If the pressure drops like when you are upside down the fuel pump will cut off.  The computer will also be fooled if the wires are cut or the sending unit is plugged up with dirty oil.  No codes for this one.  Check it out and email me back.