GMC 1976 ZEO 6083 Maintenance Manual page 705

24C- 28
ONAN MOTOR GENERATOR
ing to its manufacturer's instructions. Either spark
plug can be used as they fire simultaneously .
2. Remove the dot button on blower housing to
provide an access to view timing marks (See figure
40) .
3. Start the engine and check the timing . The
mark on the flywheel should line up with the 21°
mark on the cover.
4. Install dot button, breaker box cover and any
other hardware removed from engine .
TIMING PROCEDURE (ENGINE RUNNING
- HOT SETTING) (6KW)
1 . To check the ignition timing with unit running,
use a timing light. Connect the timing light accord-
ing to its manufacturer's instructions. Either spark
plug can be used as they fire simultaneously .
2 . A small hole on the rear portion of blower
housing provides an access to view timing marks (See
figure 40). Two marks are provided ; one for T/C
(top center) and one for 2/0 (20° BTC) .
3. Start the engine and check the timing . The 2/0
mark on the flywheel should line up in the middle of
the hole .
4. Replace breaker box cover and any other hard-
ware removed from engine.
TIMING PROCEDURE - ENGINE NOT
RUNNING - COLD SETTING
(4 AND 6 KW)
1 . Connect a continuity test lamp set across the
ignition breaker points . Touch one test prod to the
breaker box terminal to which the coil lead is con
nected and touch the other test prod to a good
ground on the engine .
2. Turn crankshaft against rotation (counter-
clockwise) until the points close. Then slowly turn
the crankshaft with rotation (clockwise).
3. The lamp should go out just as the points break
which is the time at which ignition occurs (26° BTC
- 4KW and 20° BTC - 6KW) .
SPARK PLUGS
Remove both spark plugs and install new ones
every 100 hours. Use AC No . R46S or equivalent .
Check to be sure spark plug gap is set at .020" as
shown in Figure 41 .
Figure 40-Timing Access Hole Location
IGNITION COIL
To test primary and secondary windings within
the ignition coil proceed as follows :
1 . Use a Simpson 260 VOM or equivalent .
2. Place black lead on ground (-) terminal of coil
and red lead to positive (+) terminal . Primary resist-
ance should read 4.30 (+ 10%) ohms .
3. Change resistance setting on ohmmeter . Place
ohmmeter leads inside spark plug cable holes. Sec-
ondary resistance should read 14,000 (+ 10%) ohms
(figure 42).
4. If any of the above conditions are not met,
replace coil .
Figure 41-Checking Spark Plug Gap