Troubleshooting; Fuel Starvation / Lean Mixture; Rich Mixture; Idle Too High - Polaris Ranger 500 2x4 2007 Service Manual

CARBURETION SYSTEM

TROUBLESHOOTING

Fuel Starvation / Lean Mixture

Symptoms: Hard start or no start, bog, backfire, popping
through intake / exhaust, hesitation, detonation, low power,
spark plug erosion, engine runs hot, surging, high idle, idle
speed erratic.
• No fuel in tank
• Restricted tank vent, or routed improperly
• Fuel lines or fuel valve restricted
• Fuel filter plugged
• Carburetor vent line(s) restricted
• Plugged or restricted inlet needle and seat screen or
inlet passage
• Clogged jets or passages
• Float stuck, holding inlet needle closed or inlet needle
stuck
• Float level too low
• Fuel pump inoperative
• Air leak at impulse line
• Restricted impulse line (kinked, pinched)
• Intake air leak (throttle shaft, intake ducts, airbox or air
cleaner cover)
• Ruptured vacuum slide diaphragm, Vacuum slide stuck
closed or sticky
• Improper spring
• Jet needle position incorrect
• Incorrect pilot screw adjustment

Rich Mixture

Symptoms: Fouls spark plugs, black, sooty exhaust smoke,
rough idle, poor fuel economy, engine runs rough/ misses, poor
performance, bog, engine loads up, backfire.
• Air intake restricted (inspect intake duct)
• Air filter dirty/plugged
• Choke plunger sticking, incorrectly adjusted choke
• Choke cable binding or improperly routed
• Incorrect pilot air/fuel screw adjustment
• Faulty inlet needle and seat
• Faulty inlet needle seat O-Ring
• Float level too high
4.18
• Poor fuel quality (old fuel)
• Loose jets
• Worn jet needle/needle jet or other carburetor parts
• Dirty carburetor (air bleed passages or jets)
• Weak or damaged vacuum piston return spring
• Fouled spark plug

Idle Too High

• Idle adjusted improperly/idle mixture screw damaged
• Sticky vacuum slide
• Throttle cable sticking, improperly adjusted, routed
incorrectly
• Choke cable sticking, improperly adjusted, routed
incorrectly
• Plugged or restricted idle jet

Idle Too Low

• Choke cable bending or incorrectly adjusted
• Idle speed set incorrectly
• Idle mixture screw misadjusted or damaged
• Belt dragging
• Ignition timing incorrect
• Worn jet needle/needle jet
• Plugged or restricted idle jet

Erratic Idle

• Choke cable bending or incorrectly adjusted
• Throttle cable incorrectly adjusted
• Air leaks, dirty carburetor passages (pilot circuit)
• Pilot mixture screw damaged or adjusted incorrectly
• Tight valves
• Ignition timing incorrect
• Belt dragging
• Dirty air cleaner
• Engine worn
• Spark plug fouled
• Idle speed set incorrectly (speed limiter)
• Worn jet needle/needle jet
• Plugged or restricted idle jet