Fuel Injector Troubleshooting

by Cleveland Van Cecil

Fuel injectors in an automobile deliver fuel to the engine. A fuel injector that is not working properly can cause everything from a drop in performance to the car not starting, a rough idle, misfire and a loss in power. Knowing how to troubleshoot and what to do with a faulty fuel injector can help you save money in garage visits.


It does not take much of a clog to affect engine performance. A clog can cause a "lean" fuel mixture. If you notice your car is misfiring, this may be the cause. Check to see if your check engine light is on. This often indicates that the fuel injector is clogged. Clogs are often caused by deposits of fuel contaminants in the nozzle area of the fuel injector. Detergents added to gasoline are the most common cause of deposits. If you think you have a clog, add cleaners to your fuel injection system. Cleaners are available from automotive supply and repair centers. Also buy fuel additives that prevent the accumulation of detergents in your fuel injection system.


If the fuel injector is dirty and cannot be unclogged with additives, you may need to remove it and clean it. As a preventative measure, clean your fuel injector every 25,000 to 30,000 miles. Try cleaning the fuel injector first by running the engine with cleaning fluid. Run the car for 10 minutes with the cleaning fluid inside. In many cases, the deposits from the fuel are too large or too ingrained in the system to be removed by cleaning fluid. If the fuel injector must be removed, and you are not comfortable with car repairs, take it to a service professional. This service can be very expensive.

Common Faults

Several car conditions suggest that a fuel injector is clogged or not functioning properly. If the engine will not start at all, the fuel injector may not be able to make the correct mixture of air and fuel in the engine, causing it to misfire, or not fire at all. This indicates that the fuel injector is not firing, or that it must be cleaned. If the fuel injector isn't firing, the electrical system that does the firing may not be working properly. You may see a light on the dashboard that indicates an engine failure.

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