Petrol Fuel Injector Testing

In this test first of all I did a listening test. I heard the injector with a long screwdriver. They must have a sharp tap and not a dull thud. They sounded proper and thus they were ok.

CHECK VOLTAGE

Then I did the voltage test. I checked the voltage across the battery first and then checked the voltage across the injectors one by one. The voltage across the battery was 13.1V and across each injector starting from first cylinder were 13.4V, 13.5V, 13.5V, 13.5V. The readings were all right.

LED TEST

Then I did a test using a LED tester. I connected the LED tester to the battery and connect tip to pin that has back probed connector to injector. As the injector is grounded by the ECM to fire, the test light should also be grounded to fire, and will flash. I did it one by one on each of the injector. And every injector was flashing the light. So they all passed the LED test.

DUTY CYCLE TEST

After that I used a multimeter and set it to duty cycle and watched injector firing when the engine was idling. I read at each one of the injectors one by one. The readings were as follows:-

       Cyl 1: 4.9%       Cyl2: 4.6%   Cyl 3: 4.6%    Cyl 4: 4.9%

In the next test I did the same test but the engine was accelerating. The readings were as follows:-

      Cyl 1: 18.5%     Cyl 2: 18.3%    Cyl 3: 22.3%     Cylr 4: 18.6%

HZ TEST

Then I set the meter on Hz. Then with the engine was idling then I took reading on each cylinder.

     Cyl 1: .007   Cyl2: .006   Cyl 3: .006   Cyl 4: .007

Then I did this test again with the engine revving. The readings changed and were as follows:-

 Cyl 1: .025  Cyl 2: .018  Cyl 3: .021   Cyl 4: .030

PULSE WIDTH

Then I calculated the pulse width using the formula

Pulse width ms = (% Duty Cycle * 100)/ Frequency

Then the pulse width when the engine was idling then the pulse width was as follows:-

   Cyl 1: 70 Cyl 2: 76.676  Cyl 3: 76.676    Cyl 4: 70

Then pulse width when the engine was revving

 Cyl 1: 74   Cyl 2: 101.667   Cyl 3: 106.19   Cyl 4: 62

REFLECTIONS

I think the way I tested the injector was quiet a suitable way of checking any faults in it. The reason of all the tests showed a posetive rsult and which is supposed to be.