How to diagnose fuel injector problems

Updated February 21, 2017

Fuel injectors can cause a whole host of problems that can lead to major engine damage if not diagnosed and replaced or repaired as soon as possible. To diagnose a fuel injector problem you need a keen sense of your vehicle, a little time and some basic fuel injector knowledge.

Learn about the possible problems fuel injectors can cause. A dirty fuel injector can cause fuel line problems such as misfiring, hard starting, stalling and hesitation. If you are experiencing any of these symptoms, the fuel injectors may be causing the problems.

Listen for the problems mentioned above and for other possible problems. If there are other sounds, like clanging or high idling, the problem may be something other than the fuel injector. Stick to the obvious symptoms in Step 1 to diagnose a fuel injector problem.

Check for the engine to crank. If it cranks but does not start, the likely problem can be narrowed down to the fuel pump, wiring circuit or pump relay. Bad injector relays could also be the cause. Check to see if the fuel pump runs when cranked; if so, the problem lies in the injectors themselves.

Clean the fuel injectors and examine them for excessive wear and damage. It is important to keep fuel injectors working properly. If you do, they will last you an incredible long time.


Before using testing equipment on the fuel injection system, relieve the fuel pressure by disconnecting the vacuum hose from the fuel pressure regulator and removing the fuel tank cap.

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