Nissan Repair: Car wont start, just cranking, nissan sentra, fuel pump relay

Question
hey i hope you can help me.. i have a 2002 nissan sentra 1.8 automatic... first sign was when i turn the key just crank. i turn the key on and off several times then it starts. it would turn off by its own. i do the same procedure several times but no luck in staying on.... the check engine light is on due to oxygen sensor.. i replaced all of it which was 4 on that car. before i change them i reset the code by obd device. the car starts fine and stays on.. i can drive for a while until the check engine light turns on and im back square one.. i did this twice and now its completely dont wana start... i forgot to mention this but when i turn the key to on i here fast clicking under the dash and when that clicking sound is fast and i try to start nothing.. but when i turn the key to on and the clicking sound is normal i start it, it works but die on its own.. also when that clicking sounds is fast the obd cant read anything.  but if the clicking sound is fine the obd can read something...... now the clicking sounds is not normal thats why it wont start and no read on obd reader..

thanks john

Answer
John,

A few things here.  First, remove the battery and get it tested and fully charged if not replaced.  Second, check the fuel pump relay and the fuel pump.  That is, check the fuel pressure.  You will need a pressure gauge and an adapter.  Both of these can be rented from a parts store.  If all is good then you need to check the ignition relay.  Other causes can be an aftermarket alarm.  Email me back with what you find.