The motor could be shot if left to the elements as well. The motor turns the fan + fuel pump, not motor no fuel. Also don't know what 120v source is, but if it can't keep up with startup of the burner that will pop out the button as well. Largo only makes the exterior and the coil, everything else is equipment you get on any burner.
I have had a largo 120v for 4 years now, still running the original ignitior/blower/pump, third flow switch, 4th thermostat. Once this thermostat goes though I replace it with the one I mentioned above. Easily 5000 hours on this unit