I have Well-McLain HE boiler with Fenwal control unit.
When the termostat start the boiler the igniter lit and after 45 sec the gas start burning and igniter is off, but in around 10 sec it the gas flow stops and in this case there is no lockout. Igniter start lit again and the process continue in the same way. So I have no heat now. Please help.

Start by checking the ground between the ignition control and the unit.