My father borrowed my 2009 Kubota BX2360 tractor with mower attached to the rear PTO. After disengaging the PTO, with the engine running, he got up to move some logs in his path. The engine died immediately when he got up. We have not be able to restart the tractor since. The PTO lever is in the disengaged position and despite following normal start up procedure the tractor won't start. The starter was tested and is fine. Any suggestions?