Troubleshooting
2Symptoms & remedies
| Symptom | Remedy |
|---|---|
| Engine Will Not Crank | Check battery voltage. Is battery voltage 12.4 volts or higher? Charge battery and perform a no-load test. Is battery voltage 12.4 volts or higher? • Battery defective Does starter solenoid click when ignition switch is turned to START position? • Fusible link open • Starter solenoid defective • Defective switches or wiring • Engine seized • Starter solenoid defective • Starter pinion gear sticking or damaged • Starter motor defective NO YES NO YES See Electrical Troubleshooting Repair or replace |
| Engine Cranks But Will Not Start | IMPORTANT: Perform a visual inspection first to determine if battery cables are tight and not corroded and if the battery is of sufficient size to turn the engine over at minimum cranking speed of 350 rpm. To test specific electrical components, see Electrical Section and refer to either Diagnostics or Tests & Adjustments for further guidance. • Battery defective Does fuel shutoff solenoid click when ignition switch is turned to START/RUN position? • Defective fuel shutoff solenoid • Defective switches or wiring Does engine have internal resistance? NOTE: Remove spark plugs and turn engine over by hand. Engine should rotate freely with little resistance. NO YES NO YES See Electrical Troubleshooting Repair or replace • Starter motor defective Does engine crank slow? YES NO • Piston rings or other internal components binding YES NO Is choke operating properly? Adjust YES Do spark plugs have a strong blue spark? NO YES • Defective spark plugs • Magneto kill circuit shorted to ground • Flywheel magnet weak • Ignition coil air gap not adjusted properly See Electrical Troubleshooting Are tappets adjusted properly? Adjust YES Is engine getting fuel? • Air cleaner plugged • Excessively rich fuel mixture • Water in fuel • Float needle stuck open YES NO • Not enough compression See Tests & Adjustments NO • Fuel shutoff valve closed • Fuel lines/vent plugged • Fuel pump defective • Insufficient engine vacuum |
Fault codes and symptom→remedy steps extracted from this unit’s service/owner documentation; verify against the official manual before servicing.
Aftermarket parts that fit this tractor
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Parts listed by aftermarket suppliers as fitting this tractor — leads compiled from supplier catalogs; verify the exact part for your serial number.
Available documents
Service manual
About
John Deere LT166 — tractor. Specifications and parts compiled from manufacturer documents.