Engine

If	Check
Engine Will Not Start Or Is Hard To Start	• Park brake unlocked or not adjusted correctly. • PTO is engaged. • Safety interlock switch(es) not engaged. • Starter motor or solenoid defective. • Battery weak or discharged (Low electronic control unit voltage). • Engine seized. • Faulty electronic control unit or sensor(s) • Loose or damaged wiring or connections. • Empty fuel tank. • Air filter restricted. • Clogged fuel tank filter, fuel line or vent line. • Defective fuel pump(s). • Faulty ignition coil/high tension lead. • Poor compression. • Defective head gasket. • Worn piston/piston rings stuck or not seated. • Worn or burned valves. • Worn cylinder bore. • Engine overheated. • Flywheel key sheared. • Intake system leak. • Pulse fuel pump vacuum leak. • Key switch not in proper position or faulty. • Stale or improper fuel / fuel level. • Plugged fuel filter. • Plugged air intake filter. • Spark plug wire is loose or disconnected. • Spark plug not gapped correctly. • Blown fuse. • Electrical problem - dead battery. • Choke adjusted incorrectly. See your John Deere dealer.
Engine Will Not Slow Idle	• Carburetion problems. See your John Deere dealer. • Bent or kinked throttle cable. • Bent governor control. • Incorrect governor idle control.
Engine Runs Rough or Stalls	• Plugged fuel filter. • Plugged air intake system. • Stale or improper fuel / fuel level. • Spark plug not gapped correctly. • Replace spark plug. • Choke adjusted incorrectly. See your John Deere Dealer.
Engine Knocks	• Engine oil level low. • Reduce load (Slower ground speed). • Fuel is bad. Fill tank with fresh fuel, correct octane. • Idle speed too slow. • Hydraulic lifter malfunction (For Z925M, Z945M EFI, and Z955M EFI). • Internal wear or damage.
Engine Overheats	• Low oil level. • High oil level. • Warped cylinder head. • Worn or burned valves, or improper clearance. • Faulty electronic control unit. • Broken valve spring. • Defective head gasket. • Do not operate at slow idle. Operate at fast idle. • Cooling air intake screen is dirty. • Excessive engine load. • Air intake, cooling fins, oil cooler or cooling shrouds clogged. • Plugged air intake filter. • Operating at too fast ground speed for conditions.
Engine Lacks Power	• Plugged air intake system. • Plugged fuel line or filter. • Improper type of fuel. Drain tank and fill with correct fuel. • Clean cooling fins to help prevent overheating. • Replace spark plug. • Stale fuel. • Dirty fuel injectors (Z925M, Z945M EFI, and Z955M EFI). • Weak or faulty spark plug(s). • Throttle body loose or leaking at O-ring (Z925M, Z945M EFI, and Z955M EFI). • Throttle body and throttle shaft worn (Z925M, Z945M EFI, and Z955M EFI). • Low compression. • Worn or burned valves, or improper clearance. • Faulty ignition coil or high tension lead(s). • Warped cylinder head.
Engine Uses Too Much Oil	• Find and correct oil leaks. • Incorrect engine oil. • Plugged oil filter. • Plugged air intake filter. • Crankcase overfilled. • Clogged breather or broken breather reed. • Failed head gasket. • Worn or broken piston rings. • Worn valve stem(s), valve guide(s), and/or valve stem seals. • Worn cylinder bore(s). • Debris around cooling system.
Engine Backfires Through Muffler	• Throttle should be set at 1/2 throttle before turning off machine. • Exhaust leak. • Warped cylinder head. • Defective head gasket. • Intake valve burned or sticking.
High Fuel Consumption	• Improper type of fuel. • Plugged air intake system. • Operating at too fast ground speed for conditions. • Improper valve clearance. See your John Deere Dealer. • Restricted air intake system.