monitor 422 shutts off blue flame

[megrine]

my 422 monitor heater started shutting off after start with yellow flame( it was working with no stop).
so i went ahead and i rebulit the burn chamber with new ring and burn pot that has a burn cloth glued in, gaskets...
the heater now starts fine, blue flame...after couple minutes it , the pump stops and the unit sutts off then the fan start working.
the fan start working after the heater shuts off.
i cleaned the pump, the flame rod, the exhaust, the intake, the copper tube that goes from the pump to the burn chamber.
i checked the filter near the tank(no restriction and clear).
i cleaned the filter on the side of the heater
omething?
please note that the heater was working fine( yellow flame) and started shtiing off after couple mns, when i rebuilt the burn chamber, all i got is blue flame and the heater kept shtting off.
.
am i missing something?
any advise is very appreciated...and thank you in advance

[HayZee518]

how about water flowing with your fuel? thius will cause a yellow flame and flame out.

[megrine]

thank you hayzee..
the heater use to have a yellow flame due to warped burn ring and cloth( both were replaced with a kit off ebay)
the heater now starts fine, blue flame...after couple minutes it , the pump stops and the unit sutts off then the fan start working.
the fan start working after the heater shuts off.