When I try to engage my deck the tractor starts to die. When I click the deck off it runs without problems what's up?

Could something be foul in the blades? Or a bearing down?

What if anything happened, or what symptoms was the unit having? And is the deck, and blades free of anything jamming them up as harvey suggested?

Your 314 has a seat / blade interlock switch that prevents the engine from running with the blade engaged if no one is sitting in the seat. I would check that the switch is working or bypass it and see if the motor will continue to run.

Check the seat safety switch.

I know it is an old question but I had the same problem with my 314 and it turned out that the coil was weak and when the switch was flipped to engage the PTO it took voltage from the coil making it not have enough "juice" to fire the plug and keep the mower running. Put in a new coil and works great now.

Guess this can be for folks in the future who go through the same problem :)

Easy Ed