Troubleshooting; Engine Cooling System - Polaris Sportsman 850 Service Manual

ENGINE / COOLING SYSTEM

TROUBLESHOOTING

ENGINE
Spark Plug Fouling
• Restricted air filter (main or pre-cleaner) or breather
system
• Improperly assembled air intake system
• Restricted engine breather system
• Oil contaminated with fuel
• Fuel quality poor (old) or octane too high
• PVT system calibrated incorrectly/ components worn
or mis-adjusted
• Restricted exhaust
• Spark plug cap loose or faulty
• Incorrect spark plug heat range or gap
• Weak ignition (loose coil ground, faulty coil, or stator)
• Low compression
Engine Turns Over But Fails To Start
• No fuel
• Dirt in fuel line, filter, or injectors
• Fuel pump inoperative/restricted
• Fuel valve off or restricted flow
• Tank vent plugged or pinched
• Engine flooded
• Low compression (high cylinder leakage)
• No CPS signal (debris on CPS pole, damaged CPS
causing incorrect air gap)
• No spark (spark plug fouled) ignition component failure
Engine Does Not Turn Over
• Dead battery
• Starter motor does not turn
• Engine seized, rusted, or mechanical failure
Engine Runs But Will Not Idle
• Restricted fuel system
• Low compression (valves incorrectly adjusted)
• Crankcase breather restricted
Engine Idles But Will Not Accelerate
• Spark plug fouled / weak spark
• Broken throttle cable
• Air intake obstructed
• Air box removed (reinstall all intake components)
• Reverse speed limiter limiting speed
• Incorrect ignition timing
• Restricted exhaust system
• Camshaft worn excessively
• PVT not operating properly
Engine Has Low Power
• Spark plug fouled
• Cylinder, piston, ring, or valve wear or damage (check
compression)
• PVT not operating properly
• Restricted exhaust muffler
• Camshaft worn excessively
3.80
Piston Failure - Scoring
• Lack of lubrication
• Dirt entering engine through cracks in air filter or ducts
• Engine oil dirty or contaminated (water)
Excessive Smoke and Carbon Buildup
• Excessive piston-to-cylinder clearance
• Worn rings, piston, or cylinder
• Worn valve guides or seals
• Restricted breather
• Air filter dirty or contaminated
Low Compression
• No valve clearance
• Valve not seating properly (bent valve or carbon /
debris accumulated on sealing surface)
• Cylinder head gasket leak
• Cylinder or piston worn
• Piston rings worn, leaking, broken, or sticking
• Bent valve or stuck valve
• Valve spring broken or weak
• Rocker arm sticking
Backfiring
• Fouled spark plug or incorrect plug or plug gap
• Speed limiter system malfunction
• Exhaust system air leaks
• Ignition system faulty:
• Spark plug cap cracked / broken
• Ignition coil faulty
• Ignition switch circuit faulty
• Poor connections in ignition system
• Ignition timing incorrect
• Sheared flywheel key
• Valve sticking
COOLING SYSTEM
Overheating
• Low coolant level
• Air in cooling system
• Wrong type/mix of coolant
• Faulty pressure cap or system leaks
• Restricted system (mud or debris in radiator fins
causing restriction to air flow, passages blocked in
radiator, lines, pump, or water jacket, accident
damage)
• Engine running lean (fuel system restriction)
• Fuel pump output weak
• Electrical malfunction
• Water pump failure/ Loose impeller
• Engine Coolant Temperature Sensor failure
• Cooling fan inoperative or turning too slowly (perform
current draw test)
• Low oil level
• Spark plug incorrect heat range