did you check the valve lash ? is there a bent push rod from a stuck valve

I took the filters out and looked around. Drained the tower and cleaned out the sediment. Whoever put the filter had in used silicone on the gaskets  Not rtv  but that clear stuff like you'd use on a fish aquarium. There's a small hole by the front bleeder screw in the filter plate and lid. It was plugged with silicone. Another hole had been plugged or at least significantly decreased in size. Think I got all of it cleaned out. Where is this relief valve? I didn't notice that. I got the Owners/maintenance manual and the service manual but they don't give much information. The service manual doesn't give anything about the fuel system or engine. Couldn't find anything describing the operation of the fuel system. Nothing seems to be plugged. Fuel easily gravity bleeds thru the whole system. Loosen the nuts on the injector valves on the head and it flows rather quickly.
I had the injector tips off. Cleaned the screens and swapped #1 & #3.
I haven't done very good posting pictures either. Try posting them and parts of my text disappears sometimes. 

I didn't check the lash. I did have the valve cover off. When it's running all the valves are moving. And they all appear to be moving about the same distance. None seemed loose or too tight.

When I had the injector out I looked down into the precombustion chamber. It looked rather clean and dry, dull black but dry. If it was anything other than lack of fuel causing it to not fire, it should have been wet. Unless I'm wrong. Or it could be no fuel and a burnt valve.🤔

Don't forget to check for a stuck exhaust valve. The compression release has a tendency to hold one open.

Never thought of that. But wouldn't cylinder and precombustion chamber be wet from unburnt fuel?

I found the fuel bypass valve. Was taking the adapter off to check it while trying to hold a flashlight. I ended up dropping the adapter. The adapter, stop, and spring were laying in the belly pan. The plunger either wasn't there or I didn't find it. So again I'm waiting for parts not knowing for sure if it's going to fix anything. Seemed to run too good to have been no plunger. Guess I'll find out, and maybe even find the old plunger, when the new plunger gets here. 

Therube, 
So are you saying these are known to have just one valve be stuck open by the compression release? 

Now I can say I did check the valve lash. It definitely needed it. A couple were quite loose. The bad part is it didn't make it run any better. 

I have seen valve get stuck open when the engine sits for a long time with the compression release engaged. Especially in wet climates. If the lash was out on a exhaust valve it could be that valve is open.
The next time you have the fuel nozzel out on number 3 turn the engine over in the no fuel position and put your finger over the hole and see if it blows your finger off. If you want you can compare it to another cylinder. The poor mans compression gauge.