it depends on the vehicle. Sometimes its the fuel pump. sometimes a plugged fuel filter. sometimes a blown fuse. On alot of newer cars anything that is read by the cars on board computer that has gone bad will de activate the fuel pump. When need some more specifics to help you out at this time.
If you are getting fuel and it will not start you have no spark.
You probably have the wrong type of fuel.
could be the fuel pump or regulator or the fuel pump could be plugged. if it turn key starts, there's enough pressure but if it dies, fuel is not getting to the motor.
You should check to see if you are getting spark at the wires,and fuel pressure first.
If it's not getting enough fuel it could be the fuel pump or the fuel filter.
check the fuel pump or the fuel lines or the fuel switch vavle
are you getting fuel?
if the engine turns over and it is not getting fuel, more than likely fuel filter or fuel pump problems if the car is not getting fuel.
Are you getting power to the system?
Either the fuel mix is adjusted wrong or the carb is dirty
check fuel filter,sounds like your not getting fuel,
1. If you mix the fuel with too much oil you will foul the plug. 2. If you put too little oil in the odds are good you will seize the motor.