RocketScott wrote:
Is there a switch on the cover to prevent it from starting with the cover off?
Usually, you can tape it down temporarily.
Be very careful with the igniter if you remove it - they are super fragile once they've been installed for a few years. I'd watch it while letting it attempt to ignite. If it glows red during the sequence above it is not the issue. If it is bad they are pretty universal and they're super cheap on Amazon ($15ish)
If it is failing to light the igniter is suspect #1. You can also test this by running it with the cover off and attempting to light manually using a long lighter, but if it glows it isn't the problem.
Also look for the safety limit switches. If they trip the whole thing will shut down when it tries to light. There should be one near the burner and one on the fan unit towards the top and possibly one more depending on model. They generally have a manual reset button on them and 2 wires hooked to them. In the photo above there is 1 visible, it has 2 red wires as attached.
My old furnace tripped the limit switches due to a bad capacitor that stopped the fan and thus created and over heat situation.
There aren't that many parts in a furnace. YouTube helps!