At the beginning of the winter season my boiler wasn't turning on, but I got it to work by turning on the inlet valve and just letting it feed water until the gas burners kicked in. The sight glass completely (over)filled with water to the point I couldn't see any air in the top. I was happy because my heat was working.
Now, the boiler is not engaging again. I was going to try the same tactic, but without knowing anything about boilers, let alone the kind I have, I'm afraid I might damage it. So, I just drained the water (from the rear at the inlet valve) until the low water light came on (the water in the sight glass was near the bottom). I then let in new water until the sight glass showed 4/5 full. Still no engagement of the gas burners. The pressure is floored, too. The gas pilot is burning, too.
I'm pretty sure if I just let the inlet valve feed water to the unit things will start to work again, but then what's the point of the sight glass? I don't want to try that until I know for sure it's the right move.
I'm attaching some photos of the boiler and it's readings, and I hope you can help figure out why I have no heat.