Generac Power Systems IM Series - Manual (Page 25)

ENGINE TROUBLESHOOTING
General
Most problems pertinent to engine operation may be clas­
sified as one (or a combination) of №e following:
1. Will not start
2. Hard Starting
3. Lack of power
4. Vibration
5. Overheating
6. High oil consumption
When the cause of a problem is not readily apparent, per­
form a check of the engine’s Compression, Ignition and
Carburation systems. Checkout of these systems, if per­
formed in a systematic manner, can usually be done in a
few minutes. It is the fastest and surest method of finding
the cause of a problem.
What appears to be an engine problem may sometimes
be caused by the system that the engine is driving. For
example, overloading the generator (exceeding its wat­
tage capacity) can cause the same indications as an un­
derpowered engine. A shorted condition in the generator
or in electrical loads connected to the generator can also
appear to be an underpowered engine.
Checking Engine Compression
For instructions and information on checking engine com­
pression, refer to the ENGINE SERVICE MANUAL. If
compression is poor, look for:
1. Loose spark plug(s)
2. Loose cylinder head bolts
3. Blown head gasket(s)
4. Burned valves or valve seats
5. Insufficient valve tappet clearance
6. Warped cylinder head(s)
7. Warped valve stems
8. Worn cylinder bore and/or rings
9. Broke connecting rod(s)
Check Engine ignition
Checkout and servicing of the engine ignition system is
discussed in detail, in the ENGINE SERVICE MANUAL.
To check ignition system operation, connect a SPARK
TESTER to the end of a the Spark Plug wires. Then, crank
the engine with both spark plugs removed. If a hot blue
spark jumps the Spark Tester gap, you may assume the
Ignition System is working properly. If spark jumps the
Tester gap, you may wish to try new spark plugs. If spark
does NOT jump the Tester gap, look for:
1. Defective gnition Module(s) IM1 and IM2
2. Defective Ignition Shutdown Module ISD
3. Defective Control Relay CR2
NOTE: If engine runs but misses during operation,
check to see If Ignition System Is at fault by connect
Ing the Spark Tester between the high tension Spark
Plug wire and the Spark Plugs. A spark miss will be
readily apparent
Check Carburetion
See TROUBLESHOOTING GUIDELINES. Before
making a carburetion check, make sure (a) an adequate
supply of fuel is available, (b) all fuel shutoff valve(s) are
open, and (c) fuel flow is adequate. Try adjusting the en­
gine carburetor. Check automatic choke operation and
make sure the choke is adjusted property. If engine will
not start, remove and Inspect the Spark Plug.
If Spark Plug is WET, look for:
1. Overchoking
2. Excessively rich fuel mixture
3. Water in fuel
4. Intake valve stuck open
If Spark Plug is DRY, look for:
1. Leaking carburetor gasket(s)
2. Dirty or gummy carburetor
3. Intake valve stuck closed
4. Inoperative fuel pump
A simple check to determine if fuel is reaching the com­
bustion chamber is to remove the spark plugs and pour
a small amount of gasoline through the Spark Plug hole.
Install and tighten Spark Plugs. Crank engine. If engine
fires a few times and then stops, look for the same con­
ditions as a dry plug.
Other Problems that Might Affect Engine
Operation
1. Hard Starting or Will Not Start
a. Loose drive belts or pulleys- these can cause a
"backlash" effect that will counteract engine cranking
effort.
b. Starting under load- attempting to start with heavy
electrical loads applied can often cause problems.
c. Shorted condition in the generator or in connected
electrical loads can impose a heavy load on the en­
gine, thus preventing start.
2. Vibration
a. Check for defective or damaged pulleys, drive
belts, or Rotor.
b. Check for loose mounting bolts and tighten.
3. Power Loss ■
a. Check for binding or drag in drive train (pulleys
and belts)
b. Check for defective Rotor bearing.
c. Check for Rotor contact with Stator windings.
d. Check for excessive drive belt tension.
4. Noise
a. Check for a damaged Rotor and/or Stator
b. Check for loose or damaged pulleys and drive
belts.
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