Make Toyota Model 4A-FE
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
Can you get to all the injectors? Yes
Comments:All injectors working well, it’s sound like tik....tik...tik....
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: 14.43V
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 | |
| 14.28 | 14.22 | 14.20 | 14.25 | 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.
The green LED was flashing for all injectors.
| Cyl#1 | Cyl#2 | Cyl#3 | Cyl#4 | |
| V | V | V | V | 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 | |
| 95.8 | 95.8 | 95.8 | 95.8 | 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 | |
| 78.5 | 79.1 | 79.5 | 78.2 | 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 | |
| 89.7 | 117 | 113 | 118 | 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 | |
| 457 | 445 | 436 | 452 | 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 x100)/Frequency”
Show your calculations
When Idle:
Cyl#1 : 95.8/100/89.7 = 10.68 ms
Cyl#2: 95.8/100/117 = 8.2 ms
Cyl#3: 95.8/100/113 = 8.5 ms
Cyl#4: 95.8/100/118 = 8.1 ms
When revved:
Cyl#1 : 78.5/100/457 = 1.7 ms
Cyl#2: 79.1/100/445 = 1.8 ms
Cyl#3: 79.5/100/436 = 1.8 ms
Cyl#4: 78.2/100/452 = 1.7 ms
| Cyl#1 | Cyl#2 | Cyl#3 | Cyl#4 | |
| 10.68 | 8.2 | 8.5 | 8.1 | Calculated Time at Idle (ms) |
| 1.7 | 1.8 | 1.8 | 1.7 | Calculated Time when Revved (ms) |
Give your conclusion on whether this is an acceptable way to test injectors and why?
When engine is revved, the injector is opened longer than idle, in the engine supply more fuel into combustion to be burned. The engine turn more faster automatically gives us higher RPM.
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