Signal Name/s; Injector vs Map sensor
Volt/div/range; Channel A = 20v per div, Channel B = 5v per div
Time/div/range; 20ms per div
(use letters at different points, and describe what happens there)
The beginning of the pattern where it shows a straight line is where the injector has supply voltage to it, the transistor triggers a ground circuit, this leads us to point A;
*Point A is the time span that the injector is open for (injecting fuel) at idle the injector will be open for around 2.0ms give or take. By comparing the div time to the time measured we can see that the injector open rate was about 5.0ms, which means the engine is under load as the injector is opened for a longer period of time.
*Point B this is the injectors voltage spike, as the injectors coils magnetic field is collapsed a voltage spike is created and the only way the voltage can escape is for the injector to use it.
*Point C is where the injector recovers supply voltage and the injector is off because there is no ground triggering the injector.
Moving on to the MAP signal;
*Point D shows us the MAP signal as the engine is not under load.
*Point E the engine is starting to come under load, because the MAP signal is getting lower.
*Point F the engine is under high load because the output signal of the MAP is low.
The MAP sensor helps the ECU make the right measurement as to how long the injectors should be opened for, because the MAP sensor senses engine load (vacuum) when the vacuum amount is changed this sends the ECU a signal to let it know that it needs to correspond to this by triggering the right amount of injector spray.
Signal name; Ignition primary vs primary current
Volt/div/range; Channel A = 20v per div, Channel B = 1amp per div
Time/div/range; 10ms per div
Explain the operation of the sensor or actuator using the graph;
(Use arrows at different points, and descibe what happens there)
*Point A; This shows the supply voltage to the coil.
*Point B; This part of the pattern is called the dwell time, this is the amount of time it takes the coil to charge up and fire.
*Point C; Is the collapsation of the magnetic field produced by the coil, thats why the pattern displays a huge voltage spike.
*Point E; shows no reading of current.
*Point F; this displays the signals peak current.
*Point G; the pattern has returned to no current reading.
By looking at both the patterns we can see that they relate to each other directly. If you look at the ignition primary voltage pattern, you can see off, on, firing voltage times peaks etc, if you then look at the current pattern and compare the two you can see that as the coil turns on the current does also, when the coil sends out the peak voltage, the current reading also shoots up to its highest point at the exact same time.
Signal name; Ignition primary vs Injector
Volt/div/range; Channel A = 20v per div, Channel B = 50v per div
Time/div/range; 10ms
Explain the operation of the sensor or actuator using the graph;
(Use arrows at different points and describe what happens here)
*Point A; Just the same as one of the previous tests, this shows supply voltage to the ECU.
*Point B; Also, again. This part of the pattern shows the amount of time that the injector is open for.
*Point C; Point C is also the same as a previous test. Injector gives a big voltage spike because as the injectors coil is turned off the magnetic field inside the injector is collapsed causing the big voltage spike
*Point D; shows us the supply voltage to the coil,
*Point E; is when the coil has been triggered, this period of time is also known as dwell time.
*Point F; shows the voltage peak of the coil, aswell as a few little coil oscillations at the bottom after the peak.
As you can see by looking at the graph in the picture above, you can see that both patterns correspond with each other. As the injector (top pattern) finishes dwell time and shows firing voltage so does the ignition pattern, there may-be a few micro seconds difference between both firing patterns but thats to be expected. The reason both of these patterns fire at the same time is that the engine is timed so that as the injector sprays, the ignition system sparks the spark plug allowing for combustion. You might be asking why the ignition pattern is more frequent than the injector pattern? This is because the ignition pattern is the over all ignition pattern for the engine, the injector pattern is less frequent because we are only displaying one of the injectors patterns, if all the injectors patterns were displayed we would see that each of the injectors correspond to each of the firing voltages on the ignition pattern.
Signal name; RPM vs Injectors
Volt/div/range; Channel A = 20v per div, Channel B = 10v per div
Time/div/range; 5mS per div
*Point A; Again this pattern is just a basic injector cycle pattern.
*Point B; This is the signal that the inductive type distributor puts out, it is an A/C signal. The reason for this being is that the inductive pick up is made out of magnets, so as the rotor wheels teeth pass the inductive pick up the magnetic field is altered. The magnet has a DC voltage supply to it, but as the field is altered the signal changes into a AC signal.
*Point C; Between points B & C you can see that the signal has come from a - voltage up to a + voltage, this represents an A/C signal. The line that runs through the middle of the signal is the 0v line, so anything under that line is a - voltage, anything above is a + voltage.
These patterns do relate to each other, but not directly. The inductive pattern triggers the ignition coil on and off as required, the A/C up and down signal is what triggers the coil. As explained in the previous post, the injectors and coil work in sink to allow combustion. If the distributor was malfunctioning and giving the wrong signal to the ecu, this could cause an incorrect output from the ignition coil resulting in engine mis-fire, stall etc.
Signal name; 02 vs injector
Volt/div/range; Channel A = 20v per div, Channel B = 1v per div
Time/div/range; 20mS per div
*Points A & C relate to each other. Point A is displaying the start of an injector pattern, if you observe when the pattern switches to turn on the injector you can see that the dwell time is quite long, meaning that the injector will be squirting a large amount of fuel, as the injector does this the 02 sensor is reading a rich mixture
(If the 02 sensor is showing a high voltage this displays a rich mixture). When the injector pattern returns back to a normal idle pattern (point B) we can see that the 02 sensors signal at (point D) also switches to, this signal is low, this displays that the engine is running slightly leaner, which is acceptable when an engine is not under load.
As you can see, both of these signals relate to each other, as the fuel/air injects into the cylinder the 02 sensors are waiting in the exhaust to measure the amount of unburnt fuel and amount of oxygen, what ever readings these 02 sensor takes the ECU will conpensate for a lean mixture (to much oxygen particals, not enough fuel) by injecting a larger amount of fuel. If the sensors measure a rich mixture (to much fuel not enough oxygen particals) the ECU will compensate for this by cutting the amount of fuel injected into the engine.
WS1; Petrol Fuel Injector testing.
Vehicle make; ToyotaVehicle model; Engine (1ZZ)
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, note results below;
All the injectors were functioning correctly, there was no abnormal sounds heard.
Can you access all the injectors?;
The injectors were very easy to access as we were using the 1ZZ engines in the down stairs room.
2.Check voltage to injectors when the engine is idling, or with the ignition on. This confirms that you have voltage to your injectors;
We backprobed the injectors to get an accurate reading, all the injectors were checked with the ignition on, they were 13.7v.
We then started the engine, the results are in the graph below;
We were quite surprised to see that each of the injectors measured at 13.9v, we were expecting that there would be a couple of variances just due to internal resistance, coil oscillolations etc.
3.With the engine running watch each injector firing by using an L.E.D test light, if the injector is functioning properly the light should flash to the speed in which you rev the engine to;
We started this by connecting our test probe. These are pretty simple to use, you hook one terminal of the probe up to a ground and the other up to the source you want to test.
The graph below shows which injectors showed a flashing light;
Cyl #1; 793rpm
Cyl #2; 754rpm
Cyl #3; 801rpm
Cyl #4; 734rpm
Cyl #1; 2500rpm
Cyl #2; 2500rpm
Cyl #3; 2500rpm
Cyl #4; 2500rpm
Also again the results were quite jumpy so I just took the average.
The pic above is of the calculations.
Give your conclusion on whether this is an acceptable way to test injectors and why?;
It is definitely an acceptable way to test injectors, it would be very useful if there was no oscilloscope around. Basically it is a good way of testing because you can get the readings with a multi-meter and make calculations with those, its very good if you cant afford an oscilloscope. There is a down fall to this way of testing though, taking all these readings aswell as making the calculations can be very time consuming.
WS2 flash codes;
Flash codes are a form of communication from sensors to ECU to the driver. They are used to determine any faults through-out the vehicle.
The ECU will detect any faults there may be, each fault in the vehicle has a specific fault code which is given when the system is put in diagnostic mode. Most vehicles have different steps to them into diagnostic mode.
The ECU will flash the check engine light a set amount of times to show what the flash code is, these flash codes can be noted and you can refer to the vehicles manual to look up what these codes mean.
The vehicle we used for flash codes was the toyota corolla 4afe engine. To start the procedure to extract the flash codes we first of all followed the steps in the user manual. We had to bridge terminals E1-TE1 using a jumper wire, this puts the vehicle in diagnostic mode. Sometimes people use a fuse in the jumper wire circuit to save shorts to the plugs.
We then turned the ignition on and noted any faults we came across. There was two codes that were given, the first one was;
24, we consulted the manual and that code represented (Intake air temp) circuit. Now we had to try and fix this fault correctly. First of all we located the IAT sensor, this took a little bit of looking around under the bonnet. We first looked at all the wires going into the connector, they were all fine. Then we noticed that the IATs plug was slightly unplugged, only enough so that there was no contact between the plug and the sensor. We plugged this back in, made sure that the connection was secure then we proceeded to repair the second code.
The second code was, 31 this code was (Vacuum sensor). We located the Vacuum/MAP sensor and proceeded to inspect it for visual fault. It was an obvious fault, the vacuum hose to the diaphram had been disconnected. With this unplugged the MAP sensor will not be able to operate. When then re-installed the vacuum hose, checked it for spliting and made sure there was no leaks in the hose.
Now that we had repaired all the faults found, we had to clear the codes to make sure that the problems had been correctly repaired. We did this by turning off the ignition, disconnecting the battery and leaving the engine alone for 5 mins. We turned the ignition back on and there was no more fault codes so we had repaired it properly.
The faults that had been put into the engine would effect it majorly. The vehicle would diffenately run very lean, it would also potentially be very sluggish because of the readings being given to the ECU, the ECU will not know what amount of fuel to inject etc.
Fault codes are a good way of fault diagnosis if you dont have access to a scan tool or if your vehicle is quite old and does not have an OBD system that is compatible with the scan tools. They are very useful if you have a brake down and there is no equipment handy to diagnose faults.
When the flash codes are found, we shouldnt just rely on them to diagnose problems though. Really we should do some voltage drop tests on the components that the codes are showing faults for. Also doing continuity tests to make sure that the earth on the connectors is sufficient.
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