WS1 Petrol Fuel Injector Testing

WS1 Petrol Fuel Injector Testing

 Make   TOYOTA   Model  4A-FE  Year   ...........

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.

This is a crude test to see if they are being actuated and are opening.

OK ....O.... Not OK ..........

Can you get to all the injectors? Yes ....O....  No .........

Comments:   All injectors are well operating and have good conditions. 

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: 12.86 v

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	Cyl #5	Cyl #6
13.09 v	13.21 v	13.35 v	13.33 v				Volts

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 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.

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
√	√	√	√			Tick if flashes 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	Cyl #5	Cyl #6
4.9%	4.9%	4.9%	4.9%				Duty cycle %

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	Cyl #5	Cyl #6
30%	31%	32%	31%			Duty cycle %

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	Cyl #5	Cyl #6
7Hz	7Hz	7Hz	7Hz			Hz

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	Cyl #5	Cyl #6
30Hz	30Hz	29Hz	30Hz			Hz

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

#1 cyl idle : (4.9% X 100) / 7Hz = 70 ms
#1 cyl revved : (30% X 100) / 30Hz = 100 ms
#2 cyl idle : (4.9% X 100) / 7Hz = 70 ms
#2 cyl revved : (31% X 100) / 30Hz = 103 ms
#3 cyl idle : (4.9% X 100) / 7Hz = 70 ms
#3 cyl revved : (32% X 100) / 29Hz = 110 ms
#4 cyl idle : (4.9% X 100) / 7Hz = 70 ms
#4 cyl revved : (31% X 100) / 30Hz = 103 ms

Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
70 ms	70 ms	70 ms	70 ms			Calculated Time at Idle
Cyl #1	Cyl #2	Cyl #3	Cyl #4	Cyl #5	Cyl #6
100 ms	103 ms	110 ms	103 ms			Calculated Time when revved

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

 From the petrol fuel injector testing, when the engine is idling, the duty cycle and frequency values are lower than high rpm condition. As a result, the injectors open shorter when the engine run with idling, however the injectors open longer with more fuel injection when the engine runs with higher rpm.

1. Injector's working 

All injectors are well operating and have good conditions when the engine is idling.
2. Checking voltage to the injectors when idling or key on. 

The multi meter is set to the DC volt range. A black lead touches the earth and a red lead connects main supply voltage. I watched the voltage and recorded the voltage value.
battery voltage : 12.86 v
- The Injector of back probing connection. Be careful to not puncture or damage wiring.

 

 When the engine is idling, the black lead of the multi meter is still conneted the earth and the red lead is touched each injector with the back probing pin of the red wire. I watched the voltages of injectors from Cyl #1 to Cyl #4 and recorded the voltage values. The all voltages are around at 13 v which are good. The voltages are supplied for the operation of injectors and the operating voltage for injector is same as battery voltage at DC13 v.
3. Injector firing 

 When the engine is idling, I can watch injector firing by using an LED tester or test light. First, the pin of back probing is touched the signal wire(black wire). the signal wire is grounded and ungrounded repeatedly. Secondly, the negative lead of the LED tester is connected the earth and the positive lead of LED tester is touched the the pin of the back probing from Cyl #1 to Cyl #4 then the LED flashes continuously. All injectors have good conditions.
  The injector is grounded by the ECU to fire. When the injector is grounded for its operation, the LED is off. On the other hand, when the injector is ungrounded, the LED is on. Therefore, I can check the operation of injectors with the fuel injection in the idle from the LED tester.

4. Duty cycle with engine idling

  When the engine is idling, the multi meter is set to Duty range(%). The pin of back probing is touched the signal wire (black wire). Next, the black lead of multi meter is touched the earth and the red lead of multi meter is connected the pin of back probing. And then, I watched the duty cycle and recorded this value. All cylinders have same results at 4.9% which are good for idling fuel injection duty cycle.

5. Duty cycle with engine acceleration

 The multi meter is still set to Duty range(%). The pin of back probing is touched the signal wire (black wire). Next, the black lead of multi meter is touched the earth and the red lead of multi meter is connected the pin of back probing. And then, the engine is accelerated with short, fast throttle openings. I watched the duty cycle and recorded this value. The results are slightly different in Cyl #1, Cyl #2, Cyl #3 and Cyl #4, at 30%, 31%, 29% and 31% respectively.

 From the above two duty cycle tests, the duty cycle increased in all cylinders and more fuel is injected when the engine is accelerated.

6. Frequency (Hz) with engine idling

 When the engine is idling, the multi meter is set to Hz range. The pin of back probing is touched the signal wire (black wire). Next, the black lead of multi meter is touched the earth and the red lead of multi meter is connected the pin of back probing. And then, I watched the frequency and recorded this value. All cylinders have same results at 7 Hz which are good for idling with fuel injection time.

7. Frequency (Hz) with higher engine RPM 

 The multi meter is still set to Hz range. The pin of back probing is touched the signal wire (black wire). Next, the black lead of multi meter is touched the earth and the red lead of multi meter is connected the pin of back probing. And then, the engine is accelerated with higher engine RPM. I watched the frequency and recorded this value. The results are similar in all cylinders at 30 Hz.

 From the above two frequency tests, the frequency increased in all cylinders. When more fuel is injected with higher RPM in the engine, the frequency also goes up.