Fuel Injectors; Testing; All Injectors Clicking - Chevrolet Trailblazer Service Manual

Fuel Injectors

Testing

WARNING
Stay clear of all moving engine parts. Do not wear dangling jewelry or loose clothes. Keep
power tool cords or other items that might get caught in a moving part away from fan and
pulleys. Also, do not work on an open fuel system around open flames, welders, or any
device that can cause a spark.
Checking fuel injector operation with the engine running is as simple as listening for a
clicking sound coming from the injectors. Use a mechanic's stethoscope, or a section of
rubber hose. Place the end of the stethoscope or the rubber hose onto the body of the
injector. Place the stethoscope in your ears, or place the end of the hose against your ear.
An audible clicking noise should be heard; this is the solenoid operating. If the injector
makes this noise, the injector driver circuit and computer are operating as designed.
Continue testing all the injectors this way.

All Injectors Clicking

If you've determined that all injectors are clicking, but the problem is the fuel system
continue diagnostics. Make sure that you have checked fuel pump pressure as outlined.
An easy way to determine a weak or unproductive cylinder is a cylinder drop test. This is
accomplished by cancelling one cylinder at a time, and seeing which cylinder causes the
least difference in the idle. The cylinder(s) that causes the least change is the weak
cylinder(s).
If the injectors were all clicking and the ignition system is functioning properly, remove the
injector of the suspect cylinder and have it bench tested. This is accomplished by checking
for a spray pattern from the injector itself. The injectors are placed in a device that applies
an electrical signal to the injector and a supply of pressurized solvent (not fuel) to check
the spray pattern. If no spray is achieved, replace the injector and check the engine
performance