Troubleshooting Engine - Arctic Cat ZR 120 Service Manual

Troubleshooting Engine

Problem: Engine Does Not Start (No Spark at Spark Plug)
Condition
1. Ground connections dirty — loose
2. Wiring harness shorting — disconnected
3. Emergency stop switch in DOWN position — malfunctioning
4. Tether cord improperly secured to tether switch — malfunc-
tioning
5. Spark plug fouled — damaged
Problem: Engine Does Not Start (No Fuel at Cylinders)
Condition
1. Gas tank empty
2. Gasoline contaminated
3. Fuel hose broken — pinched
4. Gas-tank vent — hose obstructed
5. Shut-off valve obstructed — damaged
6. Compression absent
Problem: Engine Does Not Start (Fuel Does Not Ignite)
Condition
1. Valve clearance poor
2. Spark absent
3. Compression low
4. Engine flooded
5. Gasoline contaminated
Problem: Engine Does Not Idle
Condition
1. Throttle stop screw turned out too far
2. Idle fuel adjuster screw out of adjustment
3. Air silencer obstructed
4. Drive clutch dirty
Problem: Engine Loses Power
Condition
1. Spark plug fouled
2. External coil faulty
3. Gas tank vent — hose obstructed
4. Compression low
5. Muffler restricted
Problem: Engine Overheats
Condition
1. Drive system adjusted incorrectly — worn — damaged
2. Rings/grooves carboned
3. Exhaust obstructed
4. Compression low — absent
5. Engine shroud obstructed
Problem: Engine Backfires
Condition
1. Spark plug fouled — damaged
Problem: Engine Stops Suddenly
Condition
1. Gas tank empty
2. Spark absent
3. Fuel filter obstructed
4. Gas tank shut-off valve in OFF position
5. Fuel hose obstructed — broken — pinched
6. Ignition coil faulty
7. Engine seized
8. Oil level low
26
Remedy
1. Check all ground connections — clean and tight
2. Repair — replace — connect wiring harness
3. Move switch to UP position — test/replace key switch/emer-
gency stop switch
4. Properly secure cord to the switch — test/replace switch
5. Clean — replace spark plug
Remedy
1. Fill tank
2. Replace gasoline
3. Replace — service hose
4. Remove obstruction — replace vent — hose
5. Remove obstruction — replace shut-off valve
6. Repair — replace damaged — worn engine components
Remedy
1. Inspect valves
2. Check for spark — see No Spark at Spark Plug sub-section
3. Service engine
4. Clear engine (using a shielded safety stand, elevate the rear
of the snowmobile and hold throttle full-open)
5. Clean tank and entire fuel system
Remedy
1. Adjust throttle stop screw
2. Adjust idle fuel adjuster screw
3. Clean air silencer
4. Clean drive clutch
Remedy
1. Replace spark plug
2. Service — replace coil
3. Service — replace vent hose
4. Service engine
5. Inspect muffler
Remedy
1. Troubleshoot — adjust drive system
2. Clean — replace rings — pistons
3. Remove obstruction
4. Repair — replace damaged — worn engine components
5. Clean shroud
Remedy
1. Clean — replace spark plug
Remedy
1. Fill tank
2. See No Spark at Spark Plug sub-section
3. Replace filter
4. Turn on valve
5. Remove obstruction — repair — replace fuel hose
6. Replace ignition coil
7. Overhaul engine
8. Add recommended oil