Lincoln 1450 will not light

[Rick_G]

OK you oven experts out there. I thought I had a great grasp of the lighting circuit on my ovens. Friday at the beginning of the rush, my top oven joined the OWS folks and quit working for the man. It had run all day and suddenly went cold, I cycled it off and on and it relit and after it got to temp again it ran ok for the rest of the night. This has happened several times in the past and has been cured by cleaning the flame sensor probe.
Today I came in early, pulled it apart and the flame sensor/pilot area was relatively clean, I cleaned it and put it back together, tried it and no fire. At this point I realized we had no pilot flame. Spent the day working on it between deliveries and this is what I found.

Pilot valve solenoid is working, I can hear it click and 4.5 inches WC gas pressure was observed at the outlet of pilot isolation valve when the pilot solenoid energized.

Ignition is working, I pulled the burner and connected it to the controller and tested it. There was a healthy blue spark. I was able to blow through the pilot gas line to the tip so it is not obstructed.

I have not touched the baffle plate on combustion air blower, and it is running and I can feel the air being pulled in by the baffle plate.

So I have Fuel, Spark and Oxygen but no fire??

Tonight, after cool-down, I am going to swap out burners with the bottom oven to see if we can run on the top until we get this resolved.

Any suggestions?

 

[bouldercreekpizza]

Had an issue on a different piece of equipment where the pilot valve solenoid worked intermittently. It would work on start up when the unit was cold but when the unit heated up it would cease functioning. Thus, I would get a few heating cycles out before a failed relight and then the unit would cool down.

 

[Rick_G]

It is working great now, I took apart the pilot orifice assy and there was a small amount of black particulate matter in there. The stuff was small enough to have passed through the holes in the orifice, and there was no restriction when I blew through the line, but after cleaning it out, and running a wire through the orifice holes the thing has run for about 12 hours now without missing a beat. When I say a small amount, I am talking about less than a dozen pieces, all appeared to be small enough to have passed through the holes.

I am still baffled as to why this was a problem, I assume the source of the foreign matter was corrosion or wear from an upstream component, but it is running now. :?: