Snyder SnyderGeneral (ArcoAire), GDE090A012AIN furnace, ignition annoyance

[hvac606]

1990 Arcoaire furnace m/n GDE090A012AIN, s/n R902800016. When it lights, the pilot flame easily travels across the right two burner set, but spread of the pilot flame to the left two burners is delayed and lights with a foosh after several seconds. The burners/ pilot rail sets were removed, cleaned ( slightly dusty) and reinstalled. Nothing changed. The gas valve opens with what appears as a initial step and then does a ramp up opening after the flame is established.

With no mechanical issues apparent, my attention goes to the gas valve. Does it not open at the correct initial step to provide enough gas to allow the spread of the flame line along the pilot rail?

Any help would be appreciated

[applianceman18007260692]

Have you tried cleaning the orifices of those 2 burners with a soft toothbrush? They may be partially clogged.

[Daveb1972]

Crossover tube alignment is crucial as well, try swapping the burners left to right, see if the problem follows the burners, or the position. If it follows the burners make sure the venturi is full open or close to full open, and that there arent any spiders living inside. Also check the flame when it is established. Is it the same on all burners? Does the flame "lift off" the surface of the burner, does it sound like a smooth hiss, or a rumbly flame blowing out type hiss? If the problem is position based, then check the orifices. The problem is not the gas valve (97% confidence) stepped gas valves and slow open gas valves either open, or not/ close or not. If they leak when closed, NG, if the dont open NG, other than that......NP.