Defected fuel injector in multicylinder engine.

Manish TomarHow can you detect that the particular fuel injector is not working properly.??

i think we can make a setup of potential sensitive valve in series just before the injection of fuel and a temperature measurement(attenuation) inside the chamber .

There are fuel injector testing machines.Fuel injectors are tested during your normal servicing, once in every six months.This is one way.
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If a fuel injector is faulty then that particular cylinder will produce a different HP than other cylinders, this will cause vibrations. You can make out from the sound of a engine that if all the cylinders are working or not.