Pontiac Fiero 1988 Service Manual page 681

6E3-C2-16 DRIVEABILITY ASSSD EMISSIONS - F U E L INJECTION (PORT)
CHART C-2A
INJECTOR BALANCE TEST
The injector balance tester is a tool used to turn the injector on for a precise
amount of time, thus spraying a measured amount of fuel into the manifold.
This causes a drop in fuel rail pressure that we can record and compare between
each injector. All injectors should have the same amount of pressure drop (± 10
kpa). Any injector with a pressure drop that is 10 kpa (or more) greater or less
than the average drop of the other injectors should be considered faulty and
replaced.
S T E P
1 !
Engine "cool down" period (10 minutes) is necessary to avoid irregular
readings due to "Hot Soak" fuel boiling. With ignition "OFF" connect fuel gauge
J347301 or equivalent to fuel pressure tap. Wrap a shop towel around fitting
while connecting gage to avoid fuel spillage.
Disconnect harness connectors at all injectors, and connect injector tester J-
34730-3, or equivalent, to one injector. On Turbo equipped engines, use adaptor
harness furnished with injector tester to energize injectors that are not
accessible. Follow manufacturers instructions for use of adaptor harness.
Ignition must be "OFF" at least 10 seconds to complete ECM shutdown cycle.
Fuel pump should run about 2 seconds after ignition is turned "ON". At this
point, insert clear tubing attached to vent valve into a suitable container and
bleed air from gauge and hose to insure accurate gauge operation. Repeat this
step until all air is bled from gauge.
STEP 2
Turn ignition "OFF" for 10 seconds and then "ON" again to get fuel pressure
to its maximum. Record this initial pressure reading. Energize tester one time
and note pressure drop at its lowest point (Disregard any slight pressure
increase after drop hits low point.). By subtracting this second pressure reading
from the initial pressure, we have the actual amount of injector pressure drop.
STEP 3
Repeat step 2 on each injector and compare the amount of drop. Usually, good
injectors will have virtually the same drop. Retest any injector that has a
pressure difference of lOkPa, either more or less than the average of the other
injectors on the engine. Replace any injector that also fails the retest. If the
pressure drop of all injectors is within lOkPa of this average, the injectors
appear to be flowing properly. Reconnect them and review Symptoms, Section
B.
NOTE:
The entire test should not be repeated more than once without
running the engine to prevent flooding. (This includes any retest on
faulty injectors).
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