my boiler stop running and wont start how can i get it to start ?

my boiler stop running and it wont start what can i do to get it running? i drain the water and started over everthing and it wont start what could be the problem? the boiler uses oil it uses oil and about 5 years old and it was running fine before until steam started to come out so we replaced the valve, and it came on yesterday but turn it off cause didnt need at the moment and now it is not turning on yes there electricity goin to it it doesnt click or even try to turn on, i turn it and nothing it doesnt click or even try to turn on, i turn it and nothing i dont hear anything coming from it