Chevrolet 70 1969 Series, Shop Manual

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ENGINE FUEL SYSTEM 6M -28
1 Relief Valve Vent to Suction Side
2 Passage to Head of Relief Valve
- Pressure Side
3 Passage From Relief Valve
- Suction Side
4 Gear Teeth Vent Cavity
5 Oil Seal Vent to Suction Side
° i*-
DRIVEN DRIVEN BODY STEEL COVER DOWEL
GEAR SHAFT i BALL
Figure
16
—Fuel Pump Valving and Rotation (Right Hand Pump
Shown)
age. If leakage exceeds one drop per minute, the
seals must be replaced. The fuel pump should
maintain a fuel pressure at the fuel inlet passage
of 50 to 70 psi at 1800 rpm engine speed. Lift on
the suction side of pump should not exceed 48 inches.
Fuel pumps are furnished in left- or right-
hand rotation according to the engine model, and
are stamped " L H IN" and "R H IN ." These pumps
are not interchangeable, nor can a pump made for
one rotation be rebuilt for the other rotation.
N O T E : The fuel pumps used on the V-type
engines are mounted on the flywheel housing and
are driven by either the camshaft gear, or by an
accessory drive gear. Fuel pumps driven by the
camshaft gears cannot be driven by the accessory
drive gear, or vise-versa, due to the difference in
drive ratios of the gears and output of the fuel
pumps.
T ES T IN G F U E L PUMP
If engine operation indicates insufficient sup­
ply of fuel to the injectors and the fuel level is not
low in the supply tank, check the fuel flow between
the restricted fitting in the fuel return passage in
the cylinder head and the fuel supply tank.
Checking Fuel Flow
1. Disconnect the flexible fuel return tube
from the fitting at the fuel tank or source of supply
and hold the open end of the pipe in a convenient
receptacle.
2. Start and run the engine at 1200 rpm (no
load) and measure the fuel flow return for a period
of one minute.
N O T E : Approximately one-half gallon of fuel
should flow from the return tube per minute.
3. Be sure all pipe connections between the
fuel supply and the pipe are tight so that no air will
be drawn into the fuel system; then immerse the
end of I the fuel tube in the fuel container. Air bub­
bles rising to the surface of the liquid will indicate
a leak on the suction side of the pump.
4. If the fuel flow is insufficient for satisfac­
tory engine performance, then:
a. Renew the element in the primary filter.
Start the engine and run it at 1200 rpm (no load)
to check the fuel flow. If the fuel flow is still un­
satisfactory, perform step "b " following:
b. Renew the element in the secondary filter.
If the fuel flow is unsatisfactory do as instructed
in step "c " following:
c. Check fuel pump as instructed previously
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L