Re: JD 318 PTO will not engage - bad connections
has it nailed. My '84 318 was doing just what you described, and after reading his sort of answers, I re-gapped my PTO and problem solved.....pretty much. Mine will engage after I first start up, and will stay engaged for as long as I want to mow, as long as I don't turn the PTO off after the engine has warmed up. Once I do that, I have to stop and let the tractor cool down before it will engage again. I attribute that to the gap closing too much as the PTO heats up, so I may see if I can open the gap a tiny bit, but I set it as close to 0.018 as I could get. I may just have to be happy a 35 year old tractor still works at all.
My 318 has been doing this exact thing lately as well. Although the PTO dash light comes on for me so a slight difference from your symptom CantKeepUp. I was suspecting a bad PTO switch or connection but I will have to go verify my PTO gap hasn't deviated from the last time I adjusted it.
1992 JD 318, 48" deck, 54" blade, 47 "chest freezer" blower, wheel weights, chains
1980 JD 314, 46" deck (sold)
1990 JD STX38 yellow deck (sold)