Troubleshooting a Toyota Fuel Injector

by Don Bowman

A Toyota fuel injector uses an electromagnet to operate the pinle. The pinle lifts through the use of the magnet and allows fuel to flow through the injector. A fuel injector has power as soon as the key is turned on. The computer supplies the ground circuit for specified amounts of time to regulate the time that the fuel injectors are open. This is calculated in milliseconds. The usual on-time or duty cycle for an injector at an idle is 2.5 to 4.0 milliseconds.

Toyota injectors do not open farther--just longer. When problems occur with fuel injectors, usually the problem is with the injectors leaking internally or externally, or they are dirty and clogged. If a cylinder exhibits a miss and the ignition system doesn't turn up any problem, the fuel injector should be examined. A fuel injector can cause a miss almost identical to an ignition miss in an engine. Look at the injectors for any leaks in the body of the injectors or at the O-ring, where they are plugged into the fuel rail. If there are no leaks, disconnect each injector one at a time and make note of how much it affects the RPM. The RPM should drop 300 to 400 RPM when the injector is disconnected. When a cylinder is found that the RPM does not drop, the injector is not functioning properly.

Use a noid light or a circuit tester, and check for power at the positive side of the injector to ensure that the wire is good. Insert the negative side of the circuit tester in the negative side of the injector connector, and the needle side of the circuit tester into the positive side of the connector. With the engine running, the light in the circuit tester should flash every time the injector is actuated. If there is no flashing but the injector has power, there is a problem with the wire to the injector driver circuit in the computer. If it does flash, the problem is with the injector. Put a long screwdriver to your ear and the other end on the injector, and listen for clicking. The clicking indicates that it is working. If no noise is heard, the injector is bad and should be replaced. If it is clicking, the injector is clogged and should be replaced.

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