3.94
9929422 R02 - 2017-2019 ACE 900 Service Manual
© Copyright Polaris Industries Inc.
TROUBLESHOOTING
ENGINE
Spark Plug Fouling
• Spark plug cap loose or faulty
• Incorrect spark plug heat range or gap
• PVT system calibrated incorrectly/ components worn
or mis-adjusted
• Fuel quality poor (old) or octane too high
• Low compression
• Restricted exhaust
• Weak ignition (loose coil ground, faulty coil, or stator)
• Restricted air filter (main or pre-cleaner) or breather
system
• Improperly assembled air intake system
• Restricted engine breather system
• Oil contaminated with fuel
Engine Turns Over But Fails To Start
• No fuel
• Dirt in fuel line or filter
• Fuel will not pass through fuel valve
• Fuel pump inoperative/restricted
• Tank vent plugged or pinched
• Engine flooded
• Low compression (high cylinder leakage)
• 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 supply
• Low compression
• Crankcase breather restricted
Engine Idles But Will Not Accelerate
• Spark plug fouled/weak spark
• Broken throttle cable
• Obstruction in air intake
• Air box removed (reinstall all intake components)
• Incorrect flywheel installation or sheared flywheel key.
• Restricted exhaust system
• Cam worn excessively
Engine Has Low Power
• Spark plug fouled
• Cylinder, piston, ring, or valve wear or damage (check
compression)
• PVT not operating properly
• Restricted exhaust muffler
• Cam worn excessively
Piston Failure - Scoring
• Lack of lubrication
• Dirt entering engine through cracks in air filter or ducts
• Engine oil dirty or contaminated
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
Piston Failure - Scoring
• Lack of lubrication
• Dirt entering engine through cracks in air filter or ducts
• Engine oil dirty or contaminated
Slow Engine Cranking
• Weak battery
• Loose Electrical connections
• Decompression Mechanism not functioning properly.
Excessive Smoke and Carbon Buildup
• Excessive piston-to-cylinder clearance
• Wet sumping due to over-full crankcase
• Worn rings, piston, or cylinder
• Worn valve guides or seals
ENGINE / COOLING SYSTEM
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