Section 3 Engine Diagnostic Tests
32
Diagnostic Repair Manual
Figure 1-8. Setting Spark Plug Gap
Figure 1-9. Spark Plug Conditions
Results
1.
Clean and gap or replace sparks plug as neces-
sary.
2.
Refer to flow chart.
Test 22 – Check Carburetion
Procedure
Before making a carburetion check, be sure fuel supply
tank has fresh, clean gasoline.
Check all shutoff valves are open and fuel flows freely
through fuel line.
Make sure choke operates properly.
If engine will not start, remove and inspect spark plug. If
spark plug is wet, look for the following:
•
Overchoking
•
Excessively rich fuel mixture
•
Water in fuel
•
Intake valve stuck open
•
Needle/float stuck open
If spark plug is dry, look for the following:
•
Leaking carburetor mounting gaskets
•
Intake valve stuck closed
•
Inoperative fuel pump
•
Plugged fuel filter(s)
•
Varnished carburetor
If engine starts hard or will not start, look for the following:
•
Physical damage to AC generator. Check Rotor for
contact with Stator.
•
Starting under load. Make sure all loads are
disconnected or turned off before attempting to
crank and start engine.
•
Be sure choke is working properly.
1.
Remove fuel line at carburetor and ensure there is
adequate fuel entering the carburetor.
2.
Remove float bowl and check for foreign matter in
bottom of carburetor bowl.
3.
The float is plastic and can be removed for access
to needle for cleaning.
4.
With all of this removed, carburetor cleaner can be
used to clean carburetor before assembly.
5.
After cleaning carburetor with approved carburetor
cleaner, blow dry with compressed air and
assemble.
Shelf life of gasoline is 30 days. A fuel stabilizer must be
used to ensure fuel is fresh at all times.
Results
If carburetor is varnished, clean or replace. Refer to flow
chart.
Test 23 – Choke Test
Procedure
If generator is surging, it may be a carburetion problem.
A lean condition can cause erratic RPM. Slowly pull
choke out to see if surging stops. If it does stop,
carburetion should be checked.
Test 24 – Check Valve Adjustment
Adjusting Valve Clearance
Improperly adjusted valves can cause various engine
related problems including, but not limited to, hard
starting, rough running and lack of power.
Adjust valve clearance with engine at room temperature.
The piston should be at top dead center (TDC) of its
compression stroke (both valves closed).
Another method is to turn engine over and position intake
valve fully open (intake valve spring compressed) and
adjust exhaust valve clearance. Turn engine over and
position exhaust valve fully open (exhaust valve spring
compressed) and adjust intake valve clearance.
002418
Engine
Intake Valve
Exhaust Valve
420
.006 ± 0.0008 inch
.008 + - 0.0008 inch
