What would cause my 03 santa fe to not start. I started it up drove it. Stated it agian put the car in reverse and it died instantly. Now it cdanks and doesnt start

OK, you changed the fuel pump, did you check all the electrical connectors to make sure they are connected completely? You should hear or feel a definite click when the connector(s) are completely seated. Next, when you turn the key to the ON (but not to the start) position, do you hear the fuel pump turn on? You should hear possibly a click, and definitely a hum if the first few seconds of turning the key to the on position. If you do hear it, then you have to have an obstruction at the end of the pump in the tank, or the fuel lines inside the tank at the pump are not completely seated/secured and may have come loose to the point that the fuel is just spraying inside the tank and not getting pumped through the lines to the engine, or the pump could be bad right out of the box. It wouldn't be the first "new" part that doesn't work right from the factory. If you do not hear anything, start by checking the fuses and relays for the fuel pump and starting /charging systems, because that would mean no power is getting to the pump. Let me know what you find.

Yeah i bench tested the pump pior to install connected my volt meter to the pump harness and get no power to the pump. I also have to power at the harness for the fuel cutoff switch but their is power at the relay. What could cause that was thinking maybe the ecm went up

Ok, sorry I forgot to tell you to actually check the cut out switch to see if it needed to be reset. When you test the connector with your volt meter, are you putting one probe of the meter into each hole on the connector and getting your reading that way? Just curious, because I usually just use a test light with a probe to hot and clip to ground. In your reply, I get a bit confused, so let's clarify. Pump end of harness is DEAD, but you DO have power going INTO the cutoff switch, but power DEAD coming OUT of the cutoff switch? If the cutoff switch has only one connector, it has to have a multiple wired (no less than 3 wires but probably four) connector, because at least one wire would be power in, one (or two) would be a ground and one would be a hot supply out of the switch, and into the pump. If you have power going into the cutoff but none coming out of the cutoff, then the cutoff switch has been tripped to the safety position and must be reset to active or running position. That is a simple power check, and if you cannot reset the switch to get power coming out of it, then it would suggest that the switch is bad or has fried somehow and needs to be replaced. I am not positive at this point, but I would think that you should be able to disconnect the harness from the switch and bypass it with jumper wires to see if the pump operates. If it does then that would again suggest the switch needs to be reset or must be replaced if it won't reset. Just let me know if I understood your reply, and if I did, try what I suggested then get back to me again. Just keep in mind, I am not being vehicle specific here, just system specific as to how the power supply to pump would or should work. There are way to many years, makes and models out there for me to be vehicle specific.