John Deere F525 difficult to start

Have JD F525 that now starts only when jumped with battery charger. Once running, runs well.
Has new 300 CCA battery.
Starting problem began slowly, sometimes taking several turns of the key. Starter would click but not engage. Now requires electrical "boost" to engage.
Any thoughts? Voltage regulator? relay?

 

Probably the solenoid. They give this kind of trouble. You may be able to nurse it along a bit by taking the starter apart, clean the shaft where the gear goes up and down and take the plunger out of the solenoid, clean it and give it a very very thin coat of grease. Clean and lube the piece that pushes the gear up and put it all back together. This solenoid is pretty expensive, so this might be worth a shot. The click you hear is the solenoid moving, and as it moves, it pulls the linkage that pushes the gear up to the engine flywheel. Sometimes when things are dirty and dry, it moves, but not far enough to go all the way to the bottom and make the final electrical connection at the contacts down there. Jumping it with a larger 500+ battery gives it that extra amperage to pull it down faster and harder to make the electrical connection.

 

Thanks Cheese, I'll give it a try.