Could mechanical resistance, hydraulic lock-up or damage be why my John Deere won’t start?
Yes, hydraulic lock or mechanical damage can prevent engine rotation.
If your engine won’t turn over at all or struggles to crank, mechanical resistance may be the cause. First, remove the spark plug or injector to relieve internal cylinder pressure and try turning the engine manually with a wrench on the crankshaft pulley. If it doesn’t rotate smoothly, check for signs of hydraulic lock—a condition caused by fuel, oil, or coolant entering the combustion chamber.
Hydraulic lock can occur if the carburetor leaks fuel into the engine while sitting. You’ll often find a soaked spark plug and strong fuel odor. Drain the excess fluid and replace the oil, as fuel may have contaminated it.
Another possibility is internal engine damage such as seized pistons, broken connecting rods, or valve train failure. Inspect the oil for metal shavings and check valve clearance if accessible. Attempting to start a hydrolocked engine can cause severe damage, so manual inspection is crucial before repeated.
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