Car will crank but no gas or spark

Running fine and turned heat on and car died. The only thing it will do is crank over the fuel pump is not kicking on and im not getting any spark at the plugs. Car will not let a hang help computer read any codes off of it.
What does ECM computer do? Tried replacing cam and crank shaft sensors with no luck, need to know what to do as I cannot afford to take it to a mechanic.