Columbia 978, Operator'S Manual

16

For repairs beyond 

the minor adjust-

ments listed here, 

contact an authorized 

service dealer. 

7

Trouble 

Shooting

Cause

Problem

Remedy

Engine fails to start

1.  Blade control handle disengaged.
2.  Spark plug wire disconnected.
3.  Fuel tank empty or stale fuel.
4.  Engine not primed.
5.   Faulty spark plug.
6.  Blocked fuel line.
7.  Engine flooding.
8.  Fuel valve (if quipped) closed.
9.  Engine not choked (if equipped with 

choke).

10. Burnt fuse. (Electric Start only).

1.  Engage blade control handle.
2.  Connect wire to spark plug.
3.  Fill tank with clean, fresh gasoline.
4.  Refer to engine manual.
5.  Clean, adjust gap, or replace.
6.  Clean fuel line.
7.  Wait a few minutes to restart, but do not prime.
8.  Open fuel valve. See engine manual.
9.  Choke engine. See engine manual.

10. Replace fuse (see Maintenance Section).

Engine runs erratic

1.  Connect and tighten spark  

plug wire.

2.  Clean fuel line; fill tank with clean, fresh 

gasoline.

3.  Clear vent.
4.  Drain fuel tank and carburetor. Refill with fresh 

fuel.

5.  Refer to engine manual.
6.  Refer to engine manual.

1.  Spark plug wire loose. 

2.  Blocked fuel line or stale fuel. 

3.  Gas cap vent plugged.
4.  Water or dirt in fuel system. 

5.  Dirty air cleaner.
6.  Carburetor out of adjustment.

Engine overheats

1.  Fill crankcase with proper oil.
2.  Refer to the engine manual packed with your 

unit.

3.  Remove blower housing and clean.
4.  Refer to engine manual.

1.  Engine oil level low.
2.  Dirty air filter. 

3.  Air flow restricted.
4.  Carburetor not adjusted properly.

Occasional skip (hesitates) 
at high speed

1.  Adjust gap to .030”. Refer to engine manual.
2.  Refer to engine manual.

1.  Spark plug gap too close.
2.  Carburetor idle mixture adjustment 

improperly set.

Idles poorly

1.  Reset gap to .030” or replace spark plug. 

Refer to engine manual.

2.  Refer to engine manual.
3.  Refer to engine manual.

1.  Spark plug fouled, faulty or gap too 

wide.

2.  Carburetor improperly adjusted.
3.  Dirty air cleaner.

1.  Cutting Blade loose or unbalanced.
2.  Bent cutting blade.

1.  Tighten blade and adapter. Balance blade
2.  Replace blade.

Excessive vibration

1.  Wheels not positioned correctly.
2.  Dull blade.

Uneven cut

1.  Place all four wheels in same height position.
2.  Sharpen or replace blade.

1.  Wet grass. 

2.  Excessive high grass. 

3.  Dull blade.

1.  Do not mow when grass is wet; 

wait until later to cut.

2.  Mow once at a high cutting height, then mow 

again at desired height or make a narrower 
cutting path.

3.  Sharpen or replace blade.

Mower will not mulch 
grass

1.  Belt not installed properly.
 
2.  Debris clogging drive operation.

1.  Checking belt for proper pulley installation and 

movement.

2.  Clean out debris.

Wheels will not propel