All burners not lighting

I have a Payne single package heating and cooling unit that runs on propane. Initially this morning when turned on it worked fine, but once thermostat shut it off it wouldn't refire when the thermostat called for more heat. I would turn it on and hear the burners fire up, but then they would shutoff for about 30 seconds and then refire over and over again. When I pulled the front panel/cover off the unit I found that all the burners weren't firing up. Either one or two burners would ignite, but the third one (left one) wouldn't.

In playing around with the problem here's what I found:

1) If I leave the front panel/cover on the unit the above conditions exist.
2) If I pull the front panel off in one, two or three ignition attempts all three burners come on. This tells me the flame sensor is working as the unit stays on when all three burners are running and the sensor is between the center burner and the one that doesn't light when the front panel is on.
3) When all three burners are on they all have the same flame, both in coloring and flame thrust. This tells me the orffices are clear.
4) The igniter is working fine. I can both hear it and see it. It clicks (arcs) about ten times.
5) My propane tank is half full and because when all three burners are on the flames are uniform and strong this tells me it's not the propane supply.

It doesn't make sense, but it's almost as if there is something weird going on in the burner chamber. I can hear the induced-draft fan running, which is suppose to create negative pressure in the burner chamber, so because the fan is running I assume there is negative pressure. One thought is, maybe there is too much negative pressure.

We had a bad storm last night, but I'm not sure if that matters.

Any help would be greatly appreciated.

Thanks in advance.

 

Presuming these burners to look like small jet airplanes, the "wings" carry the flame from one burner to the next. Try removing the burners & cleaning out the slot in each "wing" with a small strip of metal (a feeler gauge works well). You will probably find a good bit of rust.

 

Thanks Grady. I will look at that, but from what I can see the burners look very clean.

As for an update: The furnace is working this morning. At first it would take several attempts to light all burners (similar to yesterday where burners would ignite, but then shutoff over and over), but as the morning went on it progressively got better and now lights on the first, second or third attempt, which still doesn't seem right, but at least we have heat now.

Grady, or anyone, can you explain the purpose of the induced-draft fan as it relates to lighting the burners, assuming it does?

Thanks.

 

Older furnaces relied on the combustion gasses to rise through the heat exchanger and go up the chimney by convection. But that meant that the combustion gasses needed to be kept hot, reducing the amount of heat that could be extracted to heat the dwelling.

Inducer motors use a fan to force the combustion gasses through the furnace and into the vent. That allows engineers to extract more useful heat.

It could be that something is impairing the flow of combustion air through the furnace and that is interfereing with the burners lighting.

The usual cause of this problem is dirty burners or burners that are out of adjustment. If you look carefully you can probably see the carryover burner ports, "wings" on the burner that allow the flames to be transferred from burner to burner. Some defect or problem with those carryover ports is the most likely cause of the problem.

I'd watch that ignition process carefully a number of times to see if you can spot the difference between the burners that do light and the ones that are not lighting. They should all light whether the burner cover is on or off.

It could be some low probability event, but you aren't going to catch that if it is ---you'd very likely need a good repairman to identify an oddball cause.

 

I pulled the burners out today and found the carry over burner ports were clogged. Found some crusty cream colored stuff that was kinda like cream colored flour that had gotten wet and dried out. This crusty flour like stuff had plugged the ports and there were splotches of it on the pan underneath the burners as well. Haven't got a clue what the stuff is, but the burners all light instantaneously now.

Also, thanks for the tip on using the feeler gauge. All in all the repair was a piece of cake. Hardest part was drawing a picture of the wiring to make sure the wiring was reconnected correctly.

Anyhow, thanks so much for your help.

 

The crusty stuff was probably due to moisture. Quite common.
Glad you are up & running.

 

Yup, same symptoms as described and same fix here.