Chevrolet 70 1969 Series, Руководство по ремонту

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ENGINE FUEL SYSTEM 6M -27
Figure 14—Placing Injector in Comparator
7. Turn the comparator off and reset the
counter.
8. Observe the reading on the vial. Fuel output
for the N45 injector should be from 11 to 17 as
indicated on the vial.
The comparator may be used to check and se­
lect a set of injectors which will inject the same
amount of fuel in each cylinder at a given throttle
setting, thus resulting in a smooth running engine.
An injector which passes all of the above tests
may be put back into service. However, an injector
which fails to pass one or more of the tests must
be disassembled and rebuilt.
FUEL SUPPLY PUMP
The fuel pump, illustrated in figure 15, is the
positive displacement gear-type. The pump circu-
Pump Cover
Valve Plug
Gasket
Valve Spring
Relief Valve
Pump Body
Oil Seals
8 Dowel Pin
9 Drive Gear
10 Drive Shaft
11 Retaining Ball
12 Driven Shaft
13 Driven Gear
TPM-7334 -1
Figure 15—Typical Fuel Pump Assembly
lates fuel from the fuel supply tank to the fuel in­
jectors. The pump circulates the excess supply of
fuel through the injectors and the unused portion
of fuel goes back to the fuel tank by means of a
fuel return manifold located in each cylinder head
and a fuel return line.
A spring loaded relief valve, incorporated in
the pump body, normally remains in the closed
position, operating only when pressure on the out­
let side (to secondary fuel filter) becomes excess­
ive due to a plugged filter or fuel line. The valve
will open at a pressure of approximately 65 to 75
pounds per square inch, allowing fuel to return
through a passage in the body from the pressure
side to suction side of the pump. A small hole in
the pump body allows fuel oil back of the relief
valve to bleed into the gear compartment. Other­
wise, the fuel might become trapped and prevent
the valve from opening. (Refer to figure 16.)
Two oil seals are pressed into the bore in the
flanged side of the pump body with the sealing lips
of seals facing away from the fuel pump gears, as
shown in figure 15. Two tapped holes in the under­
side of pump body, between the seals, furnish a
means of attaching piping for draining off any leak-
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L