I had a similar problem on my 955. Will it run if you put the key to the on position and jump the starter solenoid? Mine was back feeding power through the relay for the glow plugs. I had the whole wire harness apart to try to find the short. I ended up just taking the relay out. I had to do something to the fuel shut off, but I can't remember exactly what I did. It had a dull illumination of the glow plug light in the dash with the key off. It was hard to see with the lights on in the barn. My problem became apparent when I needed a new battery. I put a new battery in and the next day, the new battery was junk. I cant remember exactly what I did, but it had to do with how the fuel shut off gets power. I sold the tractor, so I cant go look at it to refresh my memory.