oil burner intermittent failure to light

[mechanicalhacker]

Trying to troubleshoot an intermittent oil burner problem. It's a Wayne burner in a Miller mobile home furnace, 25-30 years old with a Sundstrand pump, burning kerosene.

The burner starts up, but typically takes a long time (~30 seconds) to fire. Once it does fire everything works fine. Sometimes, however, it doesn't fire, times out, and shuts down. When this happens it sometimes relights when the reset button is press, sometimes doesn't... and if it doesn't, it typically will work several hours later if reset. When it's not lighting, there is spark (screwdriver across the contacts), and clean kerosene runs out if the bleeder is opened, so it's not water or other contamination in the system.

Usually it works for several days, then gives trouble, then works for several days again.

The nozzle (0.6gph, which I know has a tendency to clog, but that would't cause an intermittent thing like this?) and electrodes were just replaced. Have disassembled and cleaned the pump. This morning it wouldn't light. I put a pressure gauge on the pump, it read 100 psi as it should... and the burner lit. Going to monitor the gauge next time it fails, but does anybody have any ideas on where to look next?

[hawkins111]

MIller heater

You need to remove the burner and check the electrodes again. At that time CHANGE the nozzle regardless of what you think. Since it’s a Wayne make sure the electrodes are ½ “ above the center of the nozzle, and 1/8th ahead of the nozzle tip. These measurements should put the tip of the nozzle 5/16th from the burner retention head. With a 100 PSI at the pump you should get ignition. Since the unit is 25 years old you should remove the circulating fan and clean the blower wheel. While you have the burner out be sure the fan is clean and the coupling between the pump and motor has good ends on it.

Tom

[mechanicalhacker]

Thanks Tom, I will recheck those things. As I said, I just replaced the nozzle and the electrodes. At this point it's working again, naturally, but I'm beginning to suspect something intermittent in the electrical connections to the transformer, which I'll check the next time it happens (assuming the pressure is OK).

[paul52446m]

oil burner intermittent failure to light

Trying to troubleshoot an intermittent oil burner problem. It's a Wayne burner in a Miller mobile home furnace, 25-30 years old with a Sundstrand pump, burning kerosene.

The burner starts up, but typically takes a long time (~30 seconds) to fire. Once it does fire everything works fine. Sometimes, however, it doesn't fire, times out, and shuts down. When this happens it sometimes relights when the reset button is press, sometimes doesn't... and if it doesn't, it typically will work several hours later if reset. When it's not lighting, there is spark (screwdriver across the contacts), and clean kerosene runs out if the bleeder is opened, so it's not water or other contamination in the system.

Usually it works for several days, then gives trouble, then works for several days again.

The nozzle (0.6gph, which I know has a tendency to clog, but that would't cause an intermittent thing like this?) and electrodes were just replaced. Have disassembled and cleaned the pump. This morning it wouldn't light. I put a pressure gauge on the pump, it read 100 psi as it should... and the burner lit. Going to monitor the gauge next time it fails, but does anybody have any ideas on where to look next?

One more quick note. You said you had a spark putting a screw driver across
the post When you test this way It should start a spark when you are 1/4" away and then slide the screw driver back and it should keep sparking up to 3/4", if it doesn't you might have a weak transformer. Paul