GMC 4000 Series Service Manual page 302

1 Fuel Leak-off Hose
2 Injection Nozzle Bolts
and Lock Washers
3 Compression Gauge and Hose
4 Leak-off Hose Connector
over with starter to blow loose carbon out of com­
bustion chamber and nozzle holder cavity. Use a
nozzle holder copper gasket at bottom of well and
install the com pression gauge adapter (J-21735-02)
in place of nozzle holder as shown in figure 2, using
the nozzle holder bolts to hold the adapter in place.
Connect gauge to the adapter. Be sure all connec­
tions are tight.
4. If a rear cylinder is being checked, insert
plug in the disconnected leak-off hose. When other
cylinders are being checked, join the disconnected
leak-off hoses with a two-way connector, if re­
quired. Plug and connectors are furnished as part
of com pression gauge kit.
5. Install adapter and hose (7, fig. 2) in outlet
port in hydraulic head on injection pump and place
hose in receptacle to catch fuel oil while running
the engine.
CAUTION: Under no condition should
the high pressure outlet port on the injec­
tion pump be plugged to prevent the es­
cape of fuel. The resulting hydrostatic
lock would severely damage the injection
pump mechanism when engine was started.
G M C S E R V I C E M A N U A L
5 Adapter
6 Fuel Injection Pump
Assembly
7 Adapter and Hose
8 Oil Filler Cap
Figure 2 — G a u g e and Adapter for Checking Cylinder Compression
TORO-FLOW DIESEL ENGINE
9 Overflow Valve
10 Fuel Receptacle
11 Fuel Return Line
12 Fuel Supply Pump
13 Fuel Secondary Filter
6. Start the engine and allow engine to idle at
625 rpm. Observe and record the compression
pressure shown on compression gauge.
NOTE: Do not attempt to obtain compression
pressure by cranking engine with starter.
7. Perform this operation on each cylinder.
IN JE C T IO N N O ZZLE
A S SE M B L Y
Figure 3 — C le a n in g Fuel Injection Nozzle with Brass Brush
Sec. 6B
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T-5673