How to test fuel injectors. Super fast and easy!

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Published 2023-12-13

Gramps taught me this trick a few years ago. Fuel injectors work by simply opening a plunger when supplied voltage, in which the timing is controlled by the ECU. Bad injectors don't open when fed voltage and therefore don't click. Simple! This can also be used to diagnose an injector that's stuck open, since it's already open, it won't click. Depending on the car and layout of the engine you can do this method with the fuel rail still on the engine. This was a 1993 Buick LeSabre thats been sitting for 12 years. Cranked but didn't start, had 3 bad fuel injectors. They may have been good, but just stuck due to sitting with bad gas for so long. Since I replaced the fuel tank and pump, might as well just replace all the injectors anyway to get the entire fuel system in top shape.

All Comments (5)

@elppedro77 6 months ago

Thanks for the tip, Landon. It might be a good idea to wrap one of the leads in electrical tape to avoid a possible short circuit since they are so close together.
@d4nr055 6 months ago

Just a heads up, they can still be "bad" if they click. This wont give you an idea if the injector is clogged up and spraying poorly or sticks open when pulsing. This is a great road-side test to see if its at all working electrically but you can still have a nasty misfire.
@vinnieluther6589 6 months ago

Be careful not to burn up the coil on peak and hold low resistance injectors. The ECU only allows full current very briefly to open then drops the voltage to hold it open.
@reubenmiller7988 6 months ago

Get a 2 ounce syringe. Fill with Sea Foam or similar. Use tubing or just put the syringe tip into the back of the injector. Pressurize and click the injector. This tests spray pattern and for sticking. Easier with 2 people