Injector Balance Testing

VIDEO: Injector Balance Testing

If an injector is malfunctioning, an injector balance test may help. This video is sponsored by Standard Motor Products

If you suspect that an injector is restricted or malfunctioning, an injector balance test may help isolate the bad injector. Scan tools that can disable injectors can assist you in this process. In most instances, you will select this as a function test in the scan tool menu, then the tool will allow you to disable one injector at a time.  Many times, the tool will look for engine rpm change, however, engine rpm drop may not be an effective diagnostic method when performing this test.

A more effective method is looking at the voltage changes from the upstream oxygen sensor on the bank that the disabled injector is on. Leaking injectors and some faulty injectors can be missed even when an injector is disabled. If there are other problems with the ignition system or mechanical components causing a misfire, an rpm change when an injector is turned off may not be noticed. If an injector is good, the voltage from the O2 sensor will drop to or below 100mV. Some tools may disable fuel trim during this test, but if the tool does not disable it, an increase in the short-term fuel trim may be observed as well.  Beware that if the problem is a restricted or dead injector, the long-term fuel trim may have compensated enough so that the voltage does not change.

 Another effective test is to measure the pressure loss in the fuel rail when each injector is fired and pulses for a set period of time. Use an electronic injector pulse tester for this. As each injector is energized, a fuel pressure gauge is observed to monitor the drop in fuel pressure. The electrical connectors to the other injectors are removed, isolating the injector being tested. The difference between the maximum and minimum reading is the pressure drop. Beware that this is a static test and much less fuel will be flowing than if the engine is running, so in some instances the injector might flow enough in this test, but not enough on a running engine.  Ideally, each injector should drop the same amount when opened. A variation of 1.5 to 2 psi or more is cause for concern. No change in pressure, or a very low pressure drop, is a sign the injector is restricted. A higher-than-normal pressure drop indicates a faulty injector that is flowing too much fuel for some reason. It is important to note that this test should only be done one time each injector, unless the engine is started, to prevent washing down the cylinder or hydro locking the engine.

This video is sponsored by Standard Motor Products.

You May Also Like

Mass Air Flow Sensor Cleaners

What can you do both for maintenance and for service and diagnostics to confirm a mass airflow sensors functioning properly? Andrew Markel shares the secret in this video sponsored by Auto Value and Bumper to Bumper.

The theory and operation of any mass airflow sensor is pretty basic. What you have is a wire in the Airstream entering the engine. It has current running through it. This current heats up the wire. As the air flows over this wire, it changes the resistance in the wire. The change in resistance shows the ECM, how much air is entering into the engine. But by heating up a wire that is in the Airstream entering the engine, even after the filter, it can have contaminants that can stick to that hot wire and cause faulty readings about the air entering into the engine. This can cause numerous codes because either it's under or over reporting the air entering the engine, and it's not very accurate. And using the oxygen sensor, the ECM can see issues with the mass airflow sensor. So what can you do both for maintenance and for service and diagnostics to confirm a mass airflow sensors functioning properly?

ADAS Calibrations: Limited Space

Babcox Media’s Joe Keene provides a quick overview of many examples that demonstrate ADAS work should be in play for almost everyone.

Growing Service Opportunities: Vacuum Pumps and Parking Brake Actuators

As the car parc evolves, so do service opportunities. This video is sponsored by Standard.

Software Focus: Efficient Diagnostics

Discover how to quickly retrieve codes, access exclusive repair information, and develop a strategic plan for optimal diagnostic results. This video is sponsored by Bosch.

Clutch System Components

By adopting a systematic approach and utilizing quality kits, the longevity and efficiency of the timing system can be maximized, ensuring a smoother-running engine. This video is sponsored by The Group Training Academy.

Other Posts

Deciphering Engine Misfire Codes

When the fuel/air mixture ignites, many factors must be met to pass a misfire monitor.

Standard Motor Products Expands Emission Control Program

SMP’s program features more than 3,500 parts, including EVAP, EGR and positive crankcase ventilation products.

Timing Components

By adopting a systematic approach and utilizing quality kits, the longevity and efficiency of the timing system can be maximized, ensuring a smoother-running engine. This video is sponsored by The Group Training Academy.

Wheel Bearings Components

Follow along to learn what you may encounter when dealing with a Gen 1 wheel bearing. This video is sponsored by The Group Training Academy.