Tractor Repair: New Holland TC29D Tractor, starter solenoid, holland dealer

Question
My tractor keeps blowing a fuse when you try to start.  We've had it in to the local New Holland dealer and they can't get it to duplicate.  When you turn the key to warm the glow plugs, it is fine, but when you push it in to start, it blows the fuse.  Any ideas?  The only problem we've had in the past is with the gas gauge not being accurate.  It shows 1/4 tank when it is empty.  Could the problem be in the float?

Answer
First things first. You need to remove the start wire to the starter solenoid. Turn the key and see if the fuse still blows. If it does then we have the starter eliminated. Power from your key switch runs through your neutral safety switches. Depending if the transmission is hydrostatic or a shuttle. There are two switches for hydro fwd and rev, shuttle one on the shift lever. There is also a safety switch on the pto lever or switch. Power runs through all of these switches so check the harness see if there are any exposed wire. I was looking at the parts diagram and i could not find any emissions related parts but if there are any wires to the thermostat housing and running to the pump disconnect it and try it. Buy alot of fuses, disconnect anything you can one at a time at try. Process of elimination.