Thermostat Controlled Exhaust Fan Hot Water Heater Help?

Hot water heater help? - thermostat controlled exhaust fan

I did not ignite a hot water heating with gas burners.
"Gas is on
Pilot can be lit
Magnetic thermostat to hear when the heat Holidays
Solenoid hood, when he committed, but the burner does not light

There are two electrical "devices" to control the mounted drive, it seems as if it were a cone with a tuning knob and the other cases simply cylindrical. Both have lead two son.

I think he does not have a cut gas emergency, but you know whom or for testing.

Ideas?