New to this forum. I have been chasing a stalling issue on my L4060HSTC for about a year and a half and believe I may have found the issue. Yesterday the tractor stalled and I usually check the separator to see if it is full immediately after the tractor stalls. It was about half full. I attached a length of fuel hose directly to the hose after the separator and stuck the other end directly into the tank. This got me going and I headed back to the shop. Hooked everything back up, tractor stalled again. Attached a hose to the inlet side of the separator and into the tank, separator filled about 1/3, tractor would not start. At this point I thought the separator was clogged so I removed it and cleaned what I could. Same issues again and this all pinted to the separator. Depending on your serial#, the older models have a separator with the inlet and outlet that are simply pressed into the housing. I found both to be a bit loose and figured the pump was sucking air so I tapped them back into the housing. This did not work, but had me convinced I was still sucking air intermittently and tractor would stall and sometimes restart. Again, I would always look at the separator to check the fuel level. Yesterday, I noticed the o ring that seals the plastic cup to the housing was missing. I found an o ring that was close, stretched in on and that separator filled in a few seconds when I turned the key on. Tractor started right up - so far all is well. i am guessing that sometimes air was pulled in instead of fuel. Yesterday it was about 15 degrees and metal or plastic can shrink a bit. Maybe this caused the problem. Time will tell. I have ordered the correct o ring and will install it tomorrow. Messicks has drawings that have helped me a few times with other issues and this was a help again. I have taken the bowl off before and can only assume the o ring fell out or off or whatever and I did not notice. Since the pump pulls fuel, it never leaked because of no pressure and the pump runs a few seconds after the engine is shut down. No drip or leaks. Bottom line is trouble shooting - bypass the separator, run a line into the tank where you add fuel. Do this before the separator and then after it. Air is easier to suck in than fuel. Make sure that o ring is in place.....! I plan on running the tractor today for a few hours using a wood chipper, so this will be a good test.