Troubleshooting - MTD Series 790 Operator's Manual

Troubleshooting
Problem
Engine fails to start
Cause
PTO/Blade engaged.
Engine runs erratic
Engine overheats
2. Spark plug wire disconnected.
3. Fuel tankempty, or stale fuel.
4. Choke notactivated.
5. Faulty spark plug.
6. Blocked fuel line.
7. Engine flooded.
8. Parking brake notengaged
Remedy
1. Place knob (or lever) in disengaged (OFF)
position.
2. Connect wire to spark plug.
3. Fill tank with clean, fresh (less than 30 days
old) gas.
9. Throttle control lever not in correct starting
position.
1. Unit running with CHOKE activated.
4. Place the throttle control in CHOKE position.
5. Clean, adjust gap or replace plug.
6. Clean fuel line and replace fuel filter.
7. Crankengine with throttle in FAST position.
8. Engage parking brake.
Engine hesitates at high
RPM
Engine Idles rough
Excessive vibration
Mower will not mulch grass
Uneven cut
2. Spark plug wires loose.
3. Blocked fuel line or stale fuel.
4. Ventin gas cap plugged.
5. Water or dirt in fuel system.
6. Dirty air cleaner.
1. Engine oil level low.
2. Air flow restricted.
1. Spark plug gap too close.
1. Spark plug fouled, faulty or gap too wide.
2. Dffty air cleaner.
1. Cutting blade loose or unbalanced.
2. Damaged or bent cutting blade.
1. Engine speed too low.
2. Wet grass.
3. Excessively high grass.
4. Dull blade.
1. Deck not leveled properly.
2. Dull blade.
3. Uneven tire pressure.
9. Place throttle leverto FAST position.
1. Move the throttle contol out of the CHOKE
position.
2. Connect and tighten spark plug wire.
3. Clean fuel line; fill tank with clean, fresh
gasoline and replace fuel filter, is so equipped.
4. Clear vent or replace cap if damaged.
5. Drain fuel tank. Refill wtth clean, fresh
gasoline.
6. Replace air cleaner paper element or clean
foam precleaner, is so equipped.
1. Fill crankcase with proper amount and
weight of oil.
2. Clean grass clippings and debris from around
the engine's cooling fins and blower housing.
1. Remove spark plug and resetthe gap.
1. Replace spark plug. Set plug gap.
2. Replace air cleaner element and/or clean
pre-cleaner, if so equipped.
1. Tighten blade and spindle. Balance blade.
2. Replace blade.
1. Place throttle in FAST (rabbit) position.
2. Do not mulch when grass is wet.
3. Mowonceata high cutting height, then
mow again at desired height or make a
narrower cutting swath.
4. Sharpen or replace blade.
1. Perform side-to-side deck adjustment.
2. Sharpen or replace blade.
3. Check tire pressure in all four tires.
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