Chevrolet 70 1969 Series, Shop Manual

Page: 332 / 913

ENGINE FUEL SYSTEM 6M -5
TESTING FUEL PUMP
Always check fuel pump while it is mounted
on the engine and be sure there is gasoline in the
tank.
The line from the tank to pump is the suction
side of the system. The line from pump to carbu­
retor is the pressure side of system. A leak on
the pressure side of the system would be visible
because of dripping fuel. A leak on the suction
side would not be apparent except for its effect of
reducing the volume of fuel on the pressure side.
Tighten any loose line connections and look
for bends or kinks in lines which could reduce
flow of fuel.
P R E SSU R E T E S T IN G
To make the pressure test, disconnect fuel
line at the carburetor inlet and attach a pressure
gauge between the carburetor inlet and the discon­
nected fuel line. Take the pressure reading with
the engine running. The pressure should be within
the limits given in “ Specifications'* for the par­
ticular engine. The pressure should remain con­
stant and return very slowly to zero when the
engine is stopped.
C A P A C IT Y T E S T
To make the capacity test, connect a hose to
the disconnected fuel line at the carburetor inlet.
Place the hose in a pint measure held at carbu­
retor level. Run the engine at 1200 rpm's and note
the time it takes to fill the pint measure. Refer to
"Specifications” for time required for type engine
used.
FUEL PUMP REPLACEMENT
R E M O V A L
On trucks equipped with shut-off valve in fuel
line, close valve before removing fuel pump.
1. Disconnect fuel lines at fuel pump.
N O T E : If tank line continues to siphon, remove
filler cap from fuel tank, then apply air pressure
into line forcing fuel back into tank. Make sure
filler cap is reinstalled.
2. Remove any engine accessories and piping
which may interfere with fuel pump removal.
3. Remove pump mounting bolts, then move
pump away from engine and remove gasket.
IN S T A L L A T IO N
Before installing fuel pump, be sure mounting
pad on engine is clean and that any gasket cement
and portions of old gaskets have been removed.
1. Place new fuel pump gasket at mounting pad
on engine, then set pump in place and install mount­
ing bolts.
C A U T IO N : Be sure pump arm goes under
eccentric when installing pump. To facilitate in­
stallation, crank engine so eccentric applies least
tension on pump arm.
CAUTION: To avoid pump damage, support
pump outlet fitting with wrench to avoid damage
to fuel pump.
2. Connect fuel lines and open shut-off valve
in fuel line (if equipped).
3. Reinstall any accessories or piping which
may have been removed when removing fuel pump;
then start engine and check line connections for
evidence of leakage.
4. After installation, pump should be checked
for static pressure as previously explained.
G O VERN O R
HYDRAULIC-TYPE GO VERNO R
(401M A N D 478M ENGINES)
Key numbers in text refer to Figure 7. The
engine governor system consists of shaded items
in Figure 6.
The hydraulic control mechanism is incorpor­
ated into the engine oil pump in engine crankcase.
The spinner valve is coupled to the engine oil pump
drive shaft and turns at same speed as the oil
pump (1/2 engine crankshaft speed). At one end of
the valve is a weight and at other end is a spring.
The spring holds the valve assembly in closed
position until such time as centrifugal force acting
on valve weight begins to move the valve toward
the open position. Governor valve calibration is
preset to provide governor action at proper speed.
Engine speed control is achieved by permitting
pressure from oil pump to be applied at diaphragm
(5) in slave unit (fig. 7).
When accelerator pedal is depressed to wide-
open position, the tension spring (3) in slave unit
causes the throttle plates (10) to move to wide-
open position. Diaphragm spring (4) holds dia-
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L