Chevrolet Light Duty Truck 1973 Service Manual page 464

6 M - 4 0 ENGINE FUEL
3. Remove clip and sensor from air cleaner.
Replacement
1. Install sensor and gasket assembly in air cleaner in
position as noted above.
DRILL 7 /6 4 " HOLE
IN CENTER POSITION
OF STRAP
SPOTWELDS
VACUUM DIAPHRAGM
RETAINING STRAP
Fig. 14A-Vacuum Diaphragm Replacement
General Description..........................................................6M-40
Service Procedures............................................................. 6M-40
Inspection.........................................................................6M-40
The fuel pump (fig. IP and 2P) used on all vehicles
covered in this manual is the diaphragm type. The pump
is actuated by an eccentric located on the engine
camshaft. On in-line engine, the eccentric actuates the
rocker arm. On V engines, a push rod (located between
-8
the camshaft eccentric and fuel pump) actuates the pump
rocker arm. Because of design, this pump is serviced as
an assembly only.
INSPECTION
The fuel pump (fig. 3P) should be checked to make sure
the mounting bolts and inlet and outlet connections are
tight.
TEST
Always test pump while it is mounted on the engine and
be sure there is gasoline in the tank.
The larger line from the tank to the pump is the suction side
of the system and the line from the pump to the carburetor
is the pressure side of the system. A leak on the pressure side,
therefore, would be made apparent by dripping fuel, but a
leak on the suction would not be apparent except for its
effect of reducing volume of fuel on the pressure side.
INSTALL REPLACEMENT
SENSOR ASSM. IN SAME
POSITION AS ORIGINAL ASSM.
FUEL PUMP
GENERAL DESCRIPTION
2. Press retaining clip on sensor. Support the sensor
on its side to prevent damage to the control
mechanism in the center.
3. Install air cleaner on engine and connect vacuum
hoses.
Fig. 15A--Removing Sensor Unit
INDEX
Test..................................................................................6M-40
Removal........................................................................ 6M-41
Installation.................................................................... 6M-41
1. Tighten any loose line connections and look for
bends or kinks in lines.
2. Disconnect fuel pipe at carburetor. Disconnect
distributor to coil primary wire so that engine can
be cranked without firing. Place suitable container
at end of pipe and crank engine a few revolutions.
If little or no gasoline flows from open end of pipe
then fuel pipe is clogged or pump is inoperative.
Before removing pump disconnect fuel pipe at gas
tank and outlet pipe and blow through them with
an air hose to make sure they are clear. Reconnect
pipes and retest while cranking engine.
CAUTION:
Whenever the engine i s cranked r e ­
motely at the s t a r t e r , with a s p e c i a l jumper cable
or other means the d i s t r ibutor primary lead must
be disconnected from the negative post on the c o i l
and the i g n i t i o n switch must be i n the "O N " posi­
t i o n . Failure t o do t h i s w i l l r e s u l t i n a damaged
grounding c i r c u i t i n the i g n i t i o n s w itch.
3. If fuel flows from pump in good volume from pipe
at carburetor, check fuel delivery pressure to be
certain that pump is operating within specified
limits as follows:
LIGHT DUTY TRUCK SERVICE MANUAL