my trooper only clicks when key turned. Battery old but holds a charge
Still have the battery tested, it may not be able to hold a load. And make sure all your cables are really clean, none of that black corrosion.
If you feel the battery is good you need to check the starter and the battery may hold a charge but can it pull a load. Need to do a load test on battery.
Have somebody turn the key while you whack it with a hammer. If it starts when you do this then its the solenoid going out or insufficient voltage getting to it. Many people change a starter when the only problem is poor conductivity within the circuit.
Looking for a Used Trooper in your area?
CarGurus has 142 nationwide Trooper listings starting at $3,333.
Search Isuzu Trooper Questions
Isuzu Trooper Experts