GMC 4000 Series Service Manual page 385

Sec. 6M
Page 374
FUEL INJECTION SYSTEM— TORO-FLOW ENGINE
Figure 3 3 — Control Unit Installation
same position as before removal, as marked with
dye or paint (fig. 31).
. Use lint-free cloth to prevent accidental
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loss of parts into pump cavity (fig. 31). Dropping
parts into pump cavity may necessitate pump dis­
assembly.
7. Assem ble the control unit retaining plate,
screw s (with lock washers), and spacers (fig. 32),
then install parts to retain the control unit. Tighten
screw s to 18 to 33 inch-pounds. Install lock wire
through screw heads as shown in figure 32. The
retaining plate (fig. 32) retains the control unit
and also prevents control rod from becoming dis­
engaged from lever.
NOTE: Control unit plates are available with
differences in offset. After plate screws are in­
stalled, it is important to check for clearance be­
tween inner side of plate and the control rod pin
while using screwdriver to hold the control unit
lever outward as far as possible. If there is any
contact of pin with lever or if clearance is in ex­
cess of 0.017 inch, a different plate should be
selected to provide correct clearance (
0.017 inch).
. Using new gasket, install control unit cover
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and secure with screw s and lock washers.
Figure 3 4 — O verflow V a lve C om ponents
G M C S E R V I C E M A N U A L
which are shown in figure 34, is installed as shown
in figure
threads provided in injection pump housing.
spring-loaded valve which serves to regulate the
fuel pressure within the fuel chamber surrounding
the hydraulic head assembly, and also bleeds off
any air bubbles which may be present in fuel sup­
plied by the supply pump. Excess fuel passing
through overflow valve tends to cool the hydraulic
head assem bly. The overflow valve body provides
a junction for leak-off lines (fig.
from the lines, as well as the pump supply fuel
which is forced past the overflow valve, is return­
ed to the fuel tank through fuel return line (
REMOVAL
valve and disconnect fuel return line.
valve assembly remove the assembly from injec­
tion pump body.
DISASSEMBLY
with soft jaws, then use suitable wrench to remove
the valve seat from the valve body. Remove the
valve and spring.
INSPECTION
sion. Inspect spring for damage or breakage.
ASSEMBLY
positioning the valve seat over valve, thread the
valve seat into body. Use a wrench to tighten valve
seat securely into body.
to
0 . 0 0 1
INSTALLATION
overflow valve assembly into threaded port in in­
jection pump body, using wrench on the hex-shaped
portion of valve.
leak-off lines to overflow valve body.
REMOVAL (Fig. 35)
tings from supply pump.
bolts and lock washers, then remove the supply
pump and gasket.
OVERFLOW VALVE ASSEMBLY
The overflow valve assem bly components of
, item 5. Valve assembly is screwed into
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The overflow valve assembly incorporates a
1. D isco n n ect le a k -o ff lin e s from fittin g at
2. Using wrench on hex-shaped portion of
Grip the overflow valve body in vise fitted
Inspect valve and seat for damage or corro­
Place spring and valve in valve body; then after
1. Use pipe thread sealant, and screw the
2. Install fittings and connect return line and
FUEL SUPPLY PUMP REPAIR
A N D REPLACEMENT
1. Disconnect the fuel lines and remove fit­
2. Remove the three supply pump attaching
). Fuel flowing
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, fig. ).
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