I have a john deere 240 mower that will only start if I use a battery pack jump starter. I put my battery charger on it, and that doesn't do it. The battery is fully charged. I then put the pack on, and it will start. I also need to use the battery pack to engage the electric PTO for the mowing deck. Once it's started, and the blades are running I can then take the battery pack off it, and the blades will usually stay running. Any ideas of my problem? Thanks, Denny