Chevrolet 70 1969 Series, Shop Manual

Page: 352 / 913

ENGINE FUEL SYSTEM 6M -25
Figure JO—Checking Rack
and
Plunger Freeness
Place the injector in the injector tester J-9787
(fig. 10), with the dowel in the underside of the in­
jector located in the proper slot or hole in the
adapter plate J-8538-10. Position the injector sup­
port and the handle support to the proper height.
C A U T IO N : When testing an injector
just removed from an engine, the flow
of fuel through the injector on the tester
should be the same as in the engine.
Connections on the test head of the
tester may be changed to obtain the
correct direction of flow (fig. 10).
Place the handle on top of the injector follower
then close the inlet and outlet clamps to hold the
injector in the tester. With the injector control
rack held in the N O F U E L position, push the handle
down and depress the follower to the bottom of its
stroke. Then, very slowly release the pressure on
the handle while moving the control rack back and
forth, as shown in figure 10, until the follower
reaches the top of its travel. If the rack does not
move freely, it indicates that the internal parts of
the injector are damaged or dirty.
With the injector still mounted in the injector
tester, thoroughly dry the injector with compressed
air. Then, pump up the tester and maintain a pres­
Figure
1
1
— Spray Pattern Test
sure of 1600 to 2000 psi. Inspect for leaks at the
injector filter cap gaskets, body plugs, injector
nut seal ring, injector rack hole and spray tip
orifices.
Relieve the pressure slowly when removing
the injector from the injector tester, to avoid dam ­
age to the pressure gauge.
Injector Pressure Holding T e st
Operate the pump handle to bring the pressure
up to approximately 1800 psi.
Close the fuel shut-off valve and note the pres­
sure drop. The time for a pressure drop from 1500
psi to 1000 psi should not be less than 20 seconds.
If the injector pressure drops from 1500 psi
to 1000 psi in less than 20 seconds, the injector
should be checked as follows:
1. Thoroughly dry the injector with compress­
ed air.
2. Open the tester fuel valve and operate the
pump handle to maintain the testing pressure.
3. Check for a leak at the injector rack open­
ing. A leak indicates a poor bushing-to-body fit.
4. A leak around the spray tip or seal ring
usually is caused by a loose injector nut, a damag­
ed seal ring, or a brinelled surface on the injector
nut or spray tip.
5. A leak at the filter cap indicates a loose
filter cap or a damaged filter cap gasket.
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L