1986 npr diesal batteries fully charged starter just clicks

If battery and alternator are good is starter solenoid pulling in? it may be that whilst you have a new battery it may require charging new doesn't mean fully charged, batt may have been on shelf for awhile

week or bad battery
bad starter

Since it has be sitting in storage suggest you start out by cleaning the barttery cable ends. Then try to start it. If you are still just getting clicks then try a jump start. If it still won't start, then take the fan belt off and make sure that the engine will turn by hand - with a large socket wrench that is! If it will turn by hand, it is in your starting circuit, either a weak solenoid or bad starter. If it doesn't turn then it is internal to the engine.

chk ground wires exspecially at starter and if still not sure do you have a extrior solinoid that can jump

have your starter checked out and also check you fuse that runs from you battery to your starter it sits on the fire wall

Will it turn over while being jumped? Most likely the starter is going out.

You probably already checked, but 1st thing to do is make sure the battery is good, fully charged, and cables are clean at connections, and tight. If so, Pull the starter out and bring it to a parts store where they will test it for free and let you know if it is shot. You can also remove it, attach jumper cables to it (neg. to metal body of starter, pos. to connection where battery cable was). Stand back as when you touch the pos. cable it will (if working properly) advance the gear on the shaft in the starter and then spin (to crank the engine over if it was mounted in place). This is a rather violent and very quick event, so stand back and be careful.

Fully charge battery remove and take to a shop, bench test the battery. If its not the battery remove the starter and bench test it, its either the battery or the starter.

You've got to check remove and clean your battery terminals and the connectors.Also check the main ground on the block from the battery negative terminal. Then check the tightness of the large red wire going to the starter from the positive battery terminal. And lastly, make sure the small push on terminal to the starter solenoid is tight. if not remove it and pinch it hard with your thumb and index finger. Push it back into place and see if it will start. If so while it is running check your charging systenm with a voltmeter,it should read between 13- 14.5 volts. If it does not start then jump the battery from another vehicle and then check the charging system. If your charging system is fine and the next morning you cannot get it to turn over you'll need a new battery.

make sure everything is plugged in by the battery, i had the same problem after i was climbing in there to replace the valve cover seals and accidently unplugged a wire, plugged it back in after relizing it wouldnt start and it started