Just got the 684 with a nice Rhino Loader today, and it is tricky to start. The fuel needs to be set just right and it turns over for awhile and then starts, and when cold it will die. Then just re-start and it will run if you just let it idle. While it is warming up it blows blueish smoke (incomplete fuel burn). Once it warms up the smoke goes away and it starts just fine and the throttle is responsive. The dealer said it had low power, do to low compression and that might be true. Once warm and even when cold the motor runs smooth and even. I am now thinking timing, but don't know. I still need to run compression, but I have never ran compression by removing the injectors, with my truck engines you just remove the glow plugs. The other problem is the injectors look like they are pressed in and held in with a bracket. I still need a service book, since this tractor is ruff and needs to be completely rewired, lots of body work, and paint.