OK, here’s the rest of the story, and thanks again to everyone who jumped in to help. I had continued trying to get the L3940 re-fired with the air vent cock open for a few days after starting this thread. I removed, checked, and reinstalled the fuel filter and element one more time. But at that point, it wasn’t even giving me the weak chugging while cranking the starter, so, having other fish to fry, I opted for some pro help. I insist on giving credit where it is due, so the credit for thinking this through and working this out belongs to a friend and mechanic/tech I’ll call ‘Mopar Ray’ from Empire Tractor in Waterloo NY.
No big surprise, it was indeed air in the line that wasn’t getting bled out. But in previous years I had either changed the fuel element or at least cleaned it and reassembled, and the manual’s procedure for bleeding (I quoted earlier) worked perfectly. After Mopar Ray checked other things, including making sure the injectors were getting electric juice, (not a blown fuse), he assumed that air in the lines must be the issue. Using a technique that comes from experience, he first loosened the clamp of the line coming to the filter to see if there was fuel ONLY leaking out there; then reclamped. (So basically, he uses this loosening of the hose clamps at various fuel line ends to create bleed screws where none exist.) He eventually partially loosened a fuel line going to the forward side of that air vent cock, and saw some air bubbles coming out during and immediately after cranking the starter. He then retightened that clamp. After that, the motor chugged more on attempted start-up, so, encouraged by that, he loosened that same line once more, and cranked again (no more than about 10-15 seconds!), until no bubbles we seen. (To do this operation by yourself, you need to use the clutch hold-down hook, reach up and turn the key, standing on from the driver’s right side of the tractor.) Then he got it to start; it ran a little rough but soon smoothed out to how it should sound with nice new synthetic oil and new filters. After it ran well for a minute or so, I made sure the air vent was fully closed. [Turning it all the way to the LEFT=OPEN, to the RIGHT=CLOSED.]
I'm not sure why this happened THIS time. Although I have no way of knowing now, I suspect that maybe I did screw up when I put the cleaned bowl back on, with the new fuel filter. I might NOT have seated it quite right. That, combined with starting the machine with the air vent open (for bleeding purposes) may have put a blob of air in a portion of the fuel line that the vent isn’t designed to bleed out. This is my speculation, of course, but the reason I think this is that I was repeatedly having difficulty getting the bowl aligned to reinstall, because it kept getting pushed at an angle from behind. There is a hose back there, covered by that split black plastic corrugated protective conduit, and it was being a pain. It wouldn’t allow me to get under and go straight up with the bowl the way I wanted.
So next time I do the fuel filter, I’m gonna make sure I do this: after removing the filled bowl, (when I always spill at least a little fuel, getting it off), I’m gonna totally clean the area of any fuel, so later when I turn the fuel cock back on and it refills the bowl, I’ll be able to see even the slightest amount of fuel leakage. Maybe if I had taken a little more time to do this, I might’ve caught sight of a drop of fuel, telling me that, even though it looked right, it wasn’t perfectly seated.
I’m still gonna check out the vid you mentioned, Coldfingers. Thanks again, Friends – and best to you all. I’m up and running again.
