Trouble Diagnosis - Sym PA12B Service Manual

Troubles Diagnosis
A. Engine hard to start or can not be started
Check and adjustment
Loosen carburetor drain bolt
to check if there is gasoline
inside the carburetor
Fuel supplied to
carburetor sufficient
Remove spark plug, install it
into spark plug cap, and
perform a spark test.
Good sparks
Perform cylinder
compression pressure test.
Cylinder compression
pressure normal
Re-start by following the
starting procedures
No ignition
Remove the spark plug again
and check it.
Dry spark plug
Start with choke applied
To this chapter contents
Fault condition
No fuel is supplied to
carburetor
Weak sparks, no spark
at all
Low compression
pressure or no pressure
There are some signs of
ignition; but engine
cannot be started
Wet spark plug
1. General Information
Possible causes
1. No fuel in fuel tank
2. Check if the pipes, fuel tank to carburetor
and intake vacuum, are clogged.
3. Float valve clogged
4. Lines in fuel tank evaporation system
clogged
5. Malfunction of fuel pump
6. Loosen or damaged fuel pump vacuum
hose
7. Fuel filter clogged
1. Malfunction of spark plug
2. Spark plug damaged
3. Malfunction of CDI set
4. Malfunction of AC generator
5. Ignition coil is in open or short circuit
6. Ignition coil wire open or short circuit
7. Main switch malfunction
1. Piston ring seized
2. Malfunction of cylinder valves
3. Worn cylinder and piston ring
4. Cylinder gasket leak
5. Sand hole in compression parts
1. Malfunction of throttle valve operation
2. Air leaking through intake manifold
3. Incorrect ignition timing
1. Fuel level in carburetor too high
2. Malfunction of throttle valve operation
3. Throttle valve opening too wide
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