How to check an injector pulse

Written by skip shelton Google
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How to check an injector pulse
A spark plug ignites the mist of fuel produced by the fuel injector. (Comstock/Comstock/Getty Images)

Fuel injectors require pressurised fuel lines to ensure proper injection. The pulsing of a fuel injector is a result of the charging of a solenoid that pulls open a valve. The fuel injector's moving parts will wear over time. Failed fuel injector pulsing is a result of shorted electrical lines in the fuel injection system, a broken solenoid or valve, or electrical failure in the electrical lead connecting to the fuel injector.

Skill level:


    Electrical Short Circuit Testing

  1. 1

    Disconnect all fuel injector plugs.

  2. 2

    Turn the multimeter to measure "Volts." Press the black multimeter lead to the positive terminal of the vehicle's battery. Connect the red multimeter lead to the injector plug.

  3. 3

    Start the engine. The engine will not engage but the engine will turn over. You will likely require an assistant to attempt the ignition while you perform the test. The voltage measurement should alternate between 12 volts and 0 volts as the engine rotates. This is the baseline that determines power is being delivered to the leads. If a single lead is not operational, replace it. If no power is present, diagnose the electrical failure. The most common cause of test failure is a broken multimeter tool, followed by a failure in the engine control module to control the injection process.

  4. 4

    Connect any single fuel injector plug to the fuel injector. Retest the voltage output while attempting ignition. Continue connecting plugs and retesting the first plug until all plugs are connected or lack of voltage is detected. For the final plug, connect the test plug to the respective injector and pull another injector plug to test the final injector for an electrical short.

  5. 5

    Replace any fuel injector which creates an electrical short -- no voltage measured -- when the plug is connected.

    Pulse Check

  1. 1

    Start the engine.

  2. 2

    Place a long handled screwdriver tip on the top of the fuel injector. Press the handle of the screwdriver to your ear. The clicking of the valve opening and closing will be transmitted through the screwdriver. If you hear the valve opening and closing, you can be assured the solenoid and valve are operational.

  3. 3

    Replace the injector if no solenoid operation is detected and electrical lead malfunctions and shorting are ruled out.

    Lead Testing

  1. 1

    Remove the electrical plugs from the injectors you wish to test.

  2. 2

    Turn the vehicle's ignition to "On" without starting the vehicle.

  3. 3

    Turn the multimeter to "Volts." Insert the multimeter leads into each side of the electrical plug. It does not matter into which side each lead is inserted, as long as both leads are connected; one lead should be connected in each side of the plug.

  4. 4

    Measure the incoming voltage. The voltage should be approximately 12 volts. If the voltage is too high or too low and other leads are providing 12 volts, replace the lead. If the lead is providing 12 volts and the injector is still failing, replace the injector.

Tips and warnings

  • Check for and repair fuel leaks from the injectors or fuel rail before performing electrical tests. Electrical sparks may cause fuel vapour ignition.

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