I recently rebuilt my engine. I was disappointed when starting it up that the car would not run on magneto. A friend suggested the field coil might be shorted out by the screws attaching the high volume outside oiler to the transmission hogshead. I loosened three of the six screws attaching the oiler scoop to the hogshead, the ones directly over the field coil. Tried the magneto again and it worked perfectly. The problem was indeed the 10-32 x 7/8" screws attaching the oiler to the hogshead, too long. I contacted the vendor who sold me the oiler with screws included in the kit. The vendor was aware of this potential issue and is now using shorter 3/4" screws.
Rich, just a couple of weeks ago I had a hobbyist call and tell me his field coil was not working. We ran thru all the possible scenarios of trying to determine what the problem could be. Because he was leaving for a trip the following week I shipped him another coil, he begin to tear down the engine and after pulling the trans cover he found the same problem. The screws supplied with the outside oiler were to long and shorted the field coil. While not a fan of outside oil lines I would caution everyone when accessorizing your T's make sure the part does not cause a problem with something else.
An additional potential grounding problem with the mag post outside oil line could be if the brass oil fitting that screws into the mag post base were too long and butted up against the mag post contact that goes down through the center of the base. Even if it was not touching, but only close, it might arc between the post and the fitting, if the space were small enough.
I happened to notice this when I was rebuilding my engine and, as I screwed the fitting into the mag post base, I noticed it was making contact with something before it was all the way tight. I took off the mag post to investigate and that is when I discovered the fitting butted up to the mag post. Taking apart the mag post, I screwed the fitting all the way in, then marked the curvature of the ID of the mag post base and removed the fitting, then, with a dremel tool fitted with a cutoff wheel, ground down the end of the fitting to correspond to the inside wall of the base so no crucial securing threads would be eliminated, which would have been the case if I had ground the fitting off straight.
This not only eliminated the threat of my magneto being grounded, but allowed for the maximum amount of oil to enter the outside oil line without being inhibited by the narrow space between the mag post contact and the opening of the fitting. Jim Patrick
Also need to make sure that the fitting that screws into the mag post does not contact the pin.
Fred you described in a few words what it took me three paragraphs to try and get across. LOL