I purchased a Cub Cadet 6284 with the Perkins Cat diesel engine this spring. As the fall days have gotten colder I have found it increasingly difficult to start until it was becoming almost impossible earlier last month - not yet very cold by Michigan winter standards. The starter would either not engage at all or it would engage and crank the engine just to the point that it would kick over and then disengage before the engine was running.
At first I suspected a weak battery, then connections, and even the starter, though there was just enough inconsistency to the behavior to make it difficult to pin down. I was concerned about this to the point that I started searching the forums and discovered that this is not an unusual problem with Cub diesel tractors. One post explained that the problem was caused because the circuit that energizes the starter solenoid runs through all of the safety switches and can cause enough voltage drop that the solenoid will not engage. It also recommended that the cure for this is to install a relay switch that is energized by the starter circuit and connects battery power directly to the solenoid to provide full battery voltage.
I installed a relay in the starting circuit this weekend and it definitely makes an improvement on how the tractor starts - especially when cold. I installed a 4 pin, 30 amp, 12 vold relay (Dorman part number 84601 - under $8.00 at auto parts store) and a 15 amp inline fuse on the battery side of the switched circuit. To energize the relay I took the small wire from the starter solenoid and routed it to the solenoid and grounded the other side. I then took battery power from the large positive post on the solenoid and routed it to the switched side of the relay. The other switched post I then ran to the small wire (energizing circuit) connection on the starter solenoid. See diagram at link listed in earlier post. I mounted the relay on the front of the bulkhead for the radiator (see photos).
After installing the relay the tractor now cranks much better when cold without kicking out. It acts like the battery is much stronger and I believe this is because before the voltage would drop when the starter began to crank causing the energizing voltage to the solenoid to drop thereby disengaging the starter. Note that this modification does not defeat the safety features since the circuit that energizes the relay still runs through the factor safety switches.
I hope this will be helpful to others that may be experiencing a similar situation.