WS1 Petrol Fuel Injector Testing

WS1 Petrol Fuel Injector Testing

Warning ,be careful of diesel common rail injectors .They can have very high voltage ;do not touch the electrical connectors .This worksheet is only for petrol engines that have up to 15 volts at the injectors.

1.Listen to the injectors as the engine is idling .Use stethoscope ,vacuum line or long screwdriver .Be careful of moving parts .They should sound like a sharp tap ,not a dull thud or nothing.    OK
Can you get to all the injectors?   Yes
Comment :  I  heared a small  sound from all injector .We made the test because we have to make sure they working well , if there got any problem with the fuel injectors that will have a lot of things can happen to your car like the injector will be using a lot of fuel and it will be hard to start if that is cold or hot it would be idling smoothly .

2.Check voltage to the injectors when idling or Key On .This makes sure you have battery voltage to the injectors so they can work.
Record battery voltage :14.06V
Record voltage at each injector you can get to by back probing .Be careful to not puncture or damage wiring.
Cyl#1          Cyl#2          Cyl#3          Cyl#4
14.05V       14.06V        14.06V       14.06V 

3.With engine idling ,watch injector firing by using an LED tester or test light ( with normal incandescent bulb ). Hook up test light and connect tip to pin taht 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 .
 Cyl#1          Cyl#2          Cyl#3          Cyl#4
  OK              OK              OK              OK

4.With engine idling ,watch injector firing by using a multi-meter set to read % (duty cycle). Record the readings for each cylinder at idle in the boxes below.
Cyl#1          Cyl#2          Cyl#3          Cyl#4
3.9%           3.9%            3.9%           3.9%

5.With the multi-meter still set to read % (duty cycle), accelerate the engine with short, fast throttle openings (don’t over-rev or damage the engine please), and note in the boxes below the maximum % reading you can get on the multi-meter: note the RPM.
Cyl#1          Cyl#2          Cyl#3          Cyl#4
12.5%         12.6%         9.3%           10.1%

6.Set the multi-meter to read Hz, and with the engine idling, record the readings for each cylinder in the boxes below :
Cyl#1          Cyl#2          Cyl#3          Cyl#4
15Hz           24Hz           20Hz           21Hz

 7. With the multi-meter still set to read Hz, increase the engine RPM (don’t damage the engine), and watch how the Hz changes. Record your highest reading in the boxes below: Take the readings at the same RPM as you used in question 5.
Cyl#1          Cyl#2          Cyl#3          Cyl#4
108HZ        119Hz         118Hz        125Hz

Using this formula calculate the pulse width of each injector both at idle and when the engine is revved up

“Pulse width ms= (% Duty cycle/100)/Frequency”

Show your calculations 
3.9x100/15=26ms          12.5x100/108=11.57ms
3.9x100/24=16.25ms    12.6x100/119=10.59ms
3.9x100/20=19.5ms       9.3x100/118=7.88
3.9x100/21=18.57ms    10.1x100/125=8.08ms

Cyl#1          Cyl#2          Cyl#3          Cyl#4
26ms          16.25ms     19.5ms       18.57ms
Cyl#1          Cyl#2          Cyl#3          Cyl#4
11.57ms     10.59ms     7.86ms      8.08ms

Give your conclusion on whether this is an acceptable way to test injectors and why?

We can use this method to calculate how the injectors are open when we don't have a oscilloscope to check the wave patterns and how weather that means the fuel injectors are in good condition or not , so this is an acceptable way to test injectors.

This is good way to check how much fuel is spraying by duty cycle. If this test result all good  that means ECU controll the injector properly and injector solenoid work well. 
However, this test can not guarrant  whether injector work properly like injector spray pattern is not corn shape, this test can not check it.