Furnace ignites only two burners out of four. Propane

robbietpa1

Hello
I have a american standard furnace approximately 30 years old. I have replaced the igniter, flame sensor and gas valve was replaced two years ago. The furnace tries to light on first try, it goes through all the motions and when it calls for propane it lights first two burners out of four and sometimes the last two will light after a few seconds. The furnace sometimes cycles and lights on it's own, but usually daily I have to switch it off to reset it in order for it to ignite. Any help would be useful. Thanks in advance.
Robb

JUGHNE

Could be:
Burner carryover channel (if there) needs cleaning.
Burners need cleaning.
Low gas pressure because of gas valve adjustment,
LP regulators (you should have 2) not working well. (should be replaced if original to the 30 year old furnace)
Tank needs to be at least 1/3 full.

LPG is a heavy gas and needs the recommended pressure to push it thru the entire system.
Perhaps the LP supplier has someone to check your regulators and pressure.

HVACNUT

Try to get a paperclip into the orifices. There could be webs in there. Dont be rough or use anything that could damage the holes.

ratio

Also, propane is heaver than air. If there's any making it to the orifices but not igniting, it's spilling out & collecting somewhere, waiting for an ignition source to light it off.

I'd close the gas cutoff until someone can get there to service it & make it safe.

DZoro

At 30 years old,
Suggest a qualified HVAC Company come out and BEFORE you do anything have him do a combustion analysis on your furnace.

Then if the numbers come back with a SAFE combustion report numbers. (ask him for a copy). Then proceed to purchasing new items such as burners.
Until then do as @ratio said and keep the furnace off!!!!!!!!!!!
Please be safe, and have it done properly.
D