next tip cranks but will not start all engines

[Fireplug]

Ok lets say we have a engine carb or injected that cranks put will not start up. If you have no testing tools a good place to start is to take a can of carb cleaner and spray it into the throttle body/carb and crank it over and see if it starts up and trys to run for a few sec. If it does then you have a fuel system problem, and that would include low fuel pressure, weak pump or bad pump, relay bad, fuel injector problem are just a few things in the fuel system that could be bad. If it will not even try to start then next step is spark. Check it at every plug not just 1 or 2 but ALL of them if none have any spark then move on to caps and rotors and wires and plugs and bad grounds and stuff like that.
hope this helps
Fireplug