Testing the Fuel injectors I used the Toyota 4AFE engines.
The first task was to listen to the injectors to see if they where firing, this is a very simple test and quick test to hear if they are working. After listening to all of the injectors with a stethoscope i could hear a sharp tapping sound coming from all the injectors.
Next I had to check the voltage to the injectors, but first I had to check the battery voltage to make sure the battery had a good charge, this voltage was recorded at 13.77 volts at the battery. With this checked off I was able to record the voltage at each injector, these are the readings I got,
Cyl #1 = 12.85v
Cyl #2 = 13.00v
Cyl #3 = 13.24v
Cyl #4 = 13.40v
The next test was to use a LED tester and see if it flashes on and off when the injector grounds, After testing all the the injectors the green light on my LED tester flashed has the injector opened and closed.
Next with the engine idling, I watched the injectors firing with a multi-meter set to duty cycle, these are the readings I got,
Cyl #1 = 96.5%
Cyl #2 = 96.5%
cyl #3 = 96.5%
Cyl #4 = 96.5%
These readings show the time the injector is closed not open.
Next I had the take the same readings but accelerate the engine with short, fast throttle openings.
Cyl #1 = 84%
Cyl #2 = 86%
Cyl #3 = 84%
Cyl #4 = 86%
After I got these readings, the next task to do was set the multi-meter to read Hz and with the engine idiling record the readings for each cylinder,
Cyl #1 = 9.2Hz
Cyl #2 = 9.1Hz
Cyl #3 = 9.2Hz
Cyl #4 = 9.1Hz
Then with the engine rpm brought up i took the readings again, this is what i got,
Cyl #1 = 20Hz
Cyl #2 = 20Hz
Cyl #3 = 20Hz
Cyl #4 = 20Hz
Calculating the pulse width of each injector.
Formula = Pulse width ms = (Duty Cycle/100)/Frequency
At Idle
Cyl #1 = 96.5/100 = 0.965/9.2 = 0.104ms
Cyl #2 = 96.5/100 = 0.965/9.1 = 0.106ms
Cyl #3 = 96.5/100 = 0.965/9.2 = 0.104ms
Cyl #4 = 96.5/100 = 0.965/9.1 = 0.106ms
Rpm increased
Cyl #1 = 84/100 = 0.84/20 = 0.042ms
Cyl #2 = 86/100 = 0.86/20 = 0.043ms
Cyl #3 = 84/100 = 0.84/20 = 0.042ms
Cyl #4 = 86/100 = 0.86/20 = 0.043ms
I personally would not test injectors by calculation as it is just a calculation, and if the readings i got where out the calculation would be incorrect.
