B
The three prime requirements necessary for starting and maintaining satisfactory operation
of
gasoline engines
are:
1.
A
proper fuel mixture in the cylinder
2.
Good compression in the cylinder.
3.
Good spark at the correct time, to ignite the mixture.
There are other factors which contribute to hard starting; such as too heavy a load for the engine to turn over at
low starting speed, long exhaust pipe with high back pressure, etc. These conditions may affect starting, but do
not necessarily mean the engine is improperly adjusted.
The most common symptoms of engine problems are given here, followed by the probable causes.
ENGINE
WILL
NOT
START, OR HARD
TO
START
Electrical System Problems Caused By:
Weak or dead battery.
Poor ground connection.
Defective starter.
i
Fuel System Problems Caused By:
Fuel tank empty. Improper or contaminated
fuel.
Carburetor not choked enough (cold en-
gine).
Low
cranking
speed.
Restricted cooling air circulation.
Loose fittings or defective fuel lines.
Carburetor needle valve held open by dirt or
gum.
Defective speed control or governor.
Fuel or oil leaks.
Ignition System Problems Caused By:
Loose
or
corroded electrical connections.
Ignition wires disconnected or broken.
Damaged or loose ignition module.
Faulty ignition coil.
Spark plug cable wet or broken.
Spark plug wet or dirty.
Spark ptug point gap incorrect.
Compression System Problems Caused By:
Lack of lubrication on moving parts due to
long storage.
Incorrect oil grade or
low
oil
level.
Loose or broken spark plug.
Damaged head gasket or loose cylinder
head.
Incorrect tappet clearance.
Valve stuck open due to carbon or gum on
valve stem.
Defective or incorrectly adjusted valve com-
ponents.
Worn valve guides, piston or rings.
Scored or worn cylinder walls.
3-1
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