Petrol Fuel Injector Testing (WS1)

Petrol Fuel Injector Testing

I did testings On a Toyota 4A-FE engine. I started the engine and used a stethoscope to hear the injectors opening. The injectors were very easy to access. I heard a clear sharp click as the injectors opened.

Then i checked for voltage to the injectors. The engine was idling and i got battery voltage at the injectors. We do this check to make sure that the injector is getting the right voltage for it to open properly.

CY # 1	CY # 2	CY # 3	CY # 4
13.4	13.4	13.38	13.38	Volts

Then i connected up an LED test light with the injectors at idle. I had back probed the connector to the injectors and connected the tester. As the injector gets grounded the light gets grounded to so the light comes on. The light was flashing in the rhythm to when the injectors fire.

CY # 1	CY # 2	CY # 3	CY # 4
OK	OK	OK	OK	Flashes

We back probed the injectors and connected our multimeter to read duty cycle to watch the injectors firing. We can see how much of the times  the injector is staying open. At idle we got a reading of 5.9%.

CY # 1	CY # 2	CY # 3	CY # 4
5.9	5.9	5.9	5.9	%

Then we accelerated the engine with short fast throttle opening and our duty cycle increased to 23.8%. This shows us that as the RPM increases the injectors are open longer which sprays more fuel.

CY # 1	CY # 2	CY # 3	CY # 4
23.8	23.8	23.8	23.8	%

Then we changed our setting on our multimeter to read Hz. Now we can see the frequency of how many times per second our injectors are opening and closing. At idle we got 7Hz.

CY # 1	CY # 2	CY # 3	CY # 4
7	7	7	7	Hz

Then we accelerated the engine with a short fast throttle and the frequency increased to 21Hz. 

CY # 1	CY # 2	CY # 3	CY # 4
21	21	21	21	Hz

Using the formula pulse width ms = (duty cycle / 100) / frequency/
we have to find the time in ms the injectors are open in each cycle.
Idle - 5.9 / 100 = 0.059 / 7 = 0.0084ms
Revving - 23.8 / 100 = 0.238 / 21 = 0.01ms


Idle 

CY # 1	CY # 2	CY # 3	CY # 4
0.0084	0.0084	0.0084	0.0084	Time(ms)

Revving

CY # 1	CY # 2	CY # 3	CY # 4
0.01	0.01	0.01	0.0084	Time(ms)

This is a good way to test injectors.The reading you get should be within manufactures specifications to get optimum performance fromthe engine. The testings clearly show how the injector is open longer to spray more fuel when we rev the engine. This method of testing will easily find what the problem is with the injectors.