The starter on my 1998 4cyl toyota tacoma is stuck in the on position. The only way to shut it off is to disconnect the neg battery cable.

Remove the starter relay from it's socket in the engine compartment relay box and reconnect the battery cable. If the engine cranks, your solenoid has failed closed and must be replaced. If the engine doesn't crank, borrow a 4 pole relay from somewhere else in the relay box and push it into the starter relay socket. If the engine cranks, the ignition switch is shorted to start and must be rapaired or replaced. If the engine doesn't crank, replace the starter relay. If this last case is true, you can borrow the horn relay until you get a new one. Does this make sense. Let me know if you have any questions.

We had the same problem. come to find out , its a rare case that these starters wear out ,, good know,.... easy salution... remove the starter,,,carefully remove the starter casing screws ,,,,what you will need to do is gently as possible remove the 2 contacts inside the starter and take them with you to a toyota dealership...this is necessary because their are 4 sizes of contacts, and they arent labeled as to a make or model vehicle. the total cost to replace them is 9.00$ . i know right,,, nine american dollars and about 30 min to 1 hr for completion...