Chevrolet 70 1969 Series, Shop Manual

Page: 353 / 913

ENGINE FUEL SYSTEM 6M -26
6. A "dribble” at the spray tip orifices indi­
cates a leaking valve assembly due to a damaged
surface or dirt.
Spray Pattern Test
Mount the injector in the tester (fig. 11). Place
the injector rack in the F U L L F U E L position, and
operate the pump handle until the fuel pressure is
200-250 psi. Then, close the fuel shut-off valve.
C A U T IO N : To prevent damage to
the pressure gauge, do not exceed 250
psi during this test.
Operate the injector several times in succes­
sion by operating the tester handle at approximately
40 strokes per minute as shown in figure 11; and
observe the spray pattern to see that all spray
orifices are open and injecting evenly. The begin­
ning and ending of injection should be sharp and
the fuel injected should be finely atomized.
Spray Tip Concentricity Test
The spray tip and the injector nut M U ST be
concentric within .008" to ensure correct align­
ment of the spray tip in the injector tube. Check
the concentricity in the following manner:
1. Place the injector in the concentricity gauge
J-5119 as shown in figure 12.
2. Adjust the dial indicator to " O . " Rotate the
injector 360° and note the total run-out as indicated
on the dial.
If the total run-out exceeds ,008", remove the
injector from the gauge. Loosen the injector nut,
re-center the spray tip, tighten the nut to 75 to 85
pound-feet torque and recheck the concentricity.
If, after several attempts, the spray tip cannot
be positioned satisfactorily, check the assembly of
the entire injector.
Fuel Output Test
When injectors are removed from an engine
for output testing and, if satisfactory, reinstalled
without disassembly, extreme care should be taken
to avoid reversing the fuel flow. When the flow is
reversed, dirt trapped by the filters located in the
injectors is back-flushed into the injector com­
ponents.
The fuel manifolds in Series 53 cylinder heads
direct the fuel into the injector through the filter
cap located above the fuel rack. To avoid revers­
ing the fuel flow when using adapter J-7041-88,
cross the fuel flow pipes as shown in figure 13. Do
not cross the pipes when using adapter J-7041-130.
Operate the injector in the comparator J-7041
to check the fuel output as follows:
1. Place the injector in the comparator, as
shown in figure 14. Then, turn the wheel to clamp
the injector and adapter J-7041-130 in position.
Figure 12—Checking Injector Spray Tip Concentricity
N O T E : Make sure the counter on the compara­
tor is pre-set to 1,000 strokes. If for any reason,
this setting has been altered, reset the counter to
1,000 strokes by pulling the selector wheel to be
changed to the right and rotating it to its proper
position; then, release the wheel.
2. Pull the injector rack out to the N O F U E L
position.
3. Start the comparator by turning on the
switch shown in figure 14.
4. After the comparator has started, push the
injector rack into the F U L L F U E L position and
allow the injector to operate for approximately 30
seconds to purge the air that may be in the system.
5. After 30 seconds, press fuel flow start but­
ton. This will start the flow of fuel into the vial.
The comparator will automatically stop the flow
of fuel at a pre-determined number of strokes.
6. After the fuel stops flowing into the vial,
pull the rack out to the N O F U E L position.
Figure 13—Position of Fuel Flow Pipes
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L