Fuel injection is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines.
1. First we listen to the injectors as the engine is idling. Next we use a stethoscope, vacuum line or long screwdriver. Be careful of moving parts. They should sound like a sharp tap, not a dull thud or nothing.
1. First we listen to the injectors as the engine is idling. Next we use a 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 ✓ Not OK ..........
Can you get to all the injectors? Yes✓ No .........
Comments: There was a Small tapping noise coming from the vacum line when it was held aboove the injectors
2. To Check the 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: 12.47
Record voltage at each injector you can get to by back probing. Be careful to not puncture or damage wiring.
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 | |
14.13v | 14.14v | 14.12v | 14.13v | - | - | 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 | |
5.2% | 5.3% | 5.2% | 5.2% | - | - | 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 | |
14.7% | 14.4% | 14.4% | 14.5% | - | - | Duty cycle % |
RPM + - 2000
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 | |
0.009 | 0.009 | 0.011 | 0.009 | - | - | 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 | |
0.022 | 0.020 | 0.021 | 0.20 | - | - | kHz |
RPM + - 2000
The Injector
A fuel injector is nothing but an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump in your car, and it is capable of opening and closing many times per second.
When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel -- to make as fine a mist as possible so that it can burn easily.
The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.
The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.
In order to provide the right amount of fuel, the engine control unit is equipped with a whole lot of sensors. Let's take a look at some of them.
(http://auto.howstuffworks.com/fuel-injection3.htm)
 Inside a fuel injector |
When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel -- to make as fine a mist as possible so that it can burn easily.
 A fuel injector firing |
The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.
 Fuel injectors mounted in the intake manifold of the engine |
The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.
 In this picture, you can see three of the injectors. The fuel rail is the pipe on the left. |
In order to provide the right amount of fuel, the engine control unit is equipped with a whole lot of sensors. Let's take a look at some of them.
(http://auto.howstuffworks.com/fuel-injection3.htm)
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