Carl- You aren't hallucinating. There is the manual fuel stop lever on the back corner.
Sirmombo- When you say the engine doesn't fire, how does the exhaust smell? i.e. do you smell diesel? If not, check the solenoid, below. If the solenoid is good, you might want to loosen the connection from the fuel pump to the main fuel filter. If that leaks diesel, you know the prefilter and the pump are OK. (Change the fuel filter at that point, and make sure that you clean the metal screen prefilter that is part of the fuel filter.) Try cranking again.
Diesels are pretty simple. If you are getting fuel into the cylinder, the engine will fire, unless the timing is horribly off (unlikely) or you have bent a push rod, (again unlikely). If the fuel filter and the pump check out OK, and especially if you had a dirty filter, I would check the injectors to make sure that they are clean.
Your voltage readings are...odd.
Did you do this with the engine off, but the ignition on? Regardless, your engine ground should be within a couple of ohms (not volts) of the tub ground. If it isn't, I would clean the battery (neg) to engine cable at the engine, and run a second heavy gauge wire from the engine / battery bolt over to the tub. Ideally, you want to measure the resistance relative the the battery negative until you have things pieced together. I would also check that the fuel solenoid has voltage on it when you turn the key to on. I have this faint recollection that the fuel solenoid doesn't get 12V, but I may be thinking of the fuel sender, which I know doesn't get 12V. Anyone?
Depending on the rain, you may just have gotten the engine connector wet/shorted. The engine connector isn't in the most protected of locations. I would blow the connector out with compressed air, disconnect the two halves, and clean the contacts with a small piece of 600-800 grit wet dry sand paper, and then put a little, or maybe not so little, film of dielectric grease over all the exposed metal in that connector. If it is partly disconnected, or corroded or one of the pins is out of alignment, you may not be completing the circuit.
I realize it has been a little wet in your neck of the woods lately, but mowing in the rain seems to be inviting... well, trouble, for lack of a better word. I guess it comes of knowing folks who have been hit by lightning working out in fields. Of course, that may be because I spent time near you and have some vivid memories of lakes being hit by lightning. (Yes, Virginia, the whole darn lake turns bright white.) That, and light bulbs popping when the overhead wires got hit somewhere. I miss those thunderstorms.
That fuel solenoid can get sticky, and you can clean it, but, and it is a big but, you want to be really sure to keep the area clean, and the solenoid clean of all dust and debris when it goes back in. A quick way to check it is to leave the engine cowl up, put the key in the ignition and turn it to the first position. You should hear a solenoid go click from pretty near the engine clip. If you don't hear it click, probably bad. If you do hear something, it may still be bad, as it may not be opening completely. Don't forget to look into the engine block where the solenoid threads in to make sure that it is clean as well. Many of these solenoids fail to function by sticking to crud that has come out of the fuel. You need to clean out that area before putting a new one in. If this is what happened to you, you might want to consider upgrading your diesel source and/or adding Sea Foam, or its equivalent (or both). I run Chevron or Shell diesel out here, and add Sea Foam to every 5 gallons that goes in.
YMMV.
All the best,
Peter
