Wednesday, July 20, 2011
References
All the information have been taken from google, mays book and booklets from lessons my partner by work on the diagnosis and engines. Some of info have been taken from here:
Chart of Inputs and Outputs
Engines at room 108 :)
Coolant Temperature (THW or ECT) DC volts | Cold engine 3.415v | Warmed-up engine 0.9v |
Throttle Position Sensor DC volts | Closed throttle 0.578v | Open throttle 2.010v |
Crank or RPM sensor AC volts and Hertz | Idle rpm 6.5v 1.001Hz | 2500 rpm 7.97v 1.858Hz |
MAP sensor DC volts | Idle vacuum 0.5v | No vacuum or key on engine off 1.834v |
Air Temperature (THA or IAT) DC volts | Cold engine 3.625v | Warmed-up engine 3v |
Throttle Position Switch (Idle and/or WOT) DC volts | Closed throttle None | Open throttle None |
CAM sensor AC volts & Hertz | Idle rpm 2.0v 0.080Hz | 2500 rpm 2.569v 0.154Hz |
Fuel Injector Duty cycle % | Idle 5.9% 5.9% 5.9% 5.9% | Acceleration 7.2% 7.2% 7.4% 7.2% |
Idle Air Control Duty cycle % | Idle 35% | Cranking or 2500 45% |
WS6 Oxygen Sensor on Vehicle Ford KA
Make: Ford Model: KA
1.1 Locate an oxygen sensor on your vehicle. Describe where it is located:
The oxygen sensor is located under the hood as you lift it up you can see it on top of the exhaust manifold up front of the vehicle engine bay.
The oxygen sensor is located under the hood as you lift it up you can see it on top of the exhaust manifold up front of the vehicle engine bay.
1.2 How many wires for this oxygen sensor? 4 wires.
1.3 Record the colours for each of the wires at the sensor side of the connector (not the ECU side of the connector). Then list the use of the wires. Usually a black or blue wire will be the O2 sensor signal, Grey may be the sensor ground. Heater power and ground are often white. But there may be other colours. You may have to consult a wiring diagram.
Colour : Use or Purpose:
White Heater Positive
White Heater Negative
Black Signal Positive
Grey Signal Ground
White Heater Negative
Black Signal Positive
Grey Signal Ground
1.4 What type of Oxygen Sensor is this? (tick one)
Zirconia switching sensor? …….*
Titania switching sensor? …….
Broadband Air Fuel Ratio sensor? (one cell) …….
Broadband Air Fuel Ratio sensor? (two cell) …….
This worksheet is designed for switching type sensors only. If you have a broadband sensor, see your lecturer for another worksheet.
2.0 Back probe the Oxygen Signal Wire with a pin andconnect to an oscilloscope. If you need help using the oscilloscope see your lecturer or other help sources. Check that you are connected to the Oxygen sensor signal: Run the engine and check that you are seeing a signal. Connected OK? Yes
3.0 Watch and Record Oxygen Signal pattern at 2500 rpm. Let the engine warm up and enter closed loop so you see a normal cycling pattern. You may have to hold the rpm about 2500 for half a minute to go into closed loop.
3.1 Freeze your pattern and draw or photograph it onto the graph below: Note the voltage and time per division or scale next to the graph.
3.2 How high does the voltage go? 0.908v
3.3 How low does the voltage go? 0.107v
3.4 What is the average voltage? (Some oscilloscopes have functions that will calculate the average for you. If not, just guess.) 0.500v
3.5 How many “Cross Counts” does the signal have in 10 seconds? (One cross count is when it goes from high to low, or from low to high.) List here: 14
3.6 If the signal is not cycling normally, describe what the signal does:
The signal is cycling normally therefore I cannot describe what the signal does if it wasn't normal.
The signal is cycling normally therefore I cannot describe what the signal does if it wasn't normal.
4.0 Watch and Record Oxygen Signal pattern at Idle rpm.Let the engine warm up and enter closed loop so you see a normal cycling pattern. You may have to hold the rpm about 2500 for half a minute to go into closed loop. Then let the RPM come down to idle.
4.1 Freeze your pattern and draw or photograph it onto the graph below: Note the voltage and time per division or scale next to the graph.
4.2 How high does the voltage go? 0.857v
4.3 How low does the voltage go? 0.167v
4.4 What is the average voltage? (Some oscilloscopes have functions that will calculate the average for you. If not, just guess.) 0.450v
4.5 How many “Cross Counts” does the signal have in 10 seconds? (One cross count is when it goes from high to low, or from low to high.) List here: 6
4.6 If the signal is not cycling normally, describe what the signal does:
The signal is cycling normally.
The signal is cycling normally.
5.0 Make this Oxygen Sensor go rich by accelerating once or twice. (The fuel system should normally make the system go rich when you do a sudden acceleration.) Push on the accelerator quickly but don’t let the rpm go high enough to hurt the engine. (If you act like you will hurt the engine you will be asked to leave lab.) The signal should go over 0.85V.
5.1 Freeze your pattern as it goes rich and draw or photograph it onto the graph below: Note the voltage and time per division or scale next to the graph.
5.2 How high does the Oxygen sensor voltage go?0.859v
5.3 If this signal is not going high normally, describe what the signal does:
The signal is working normally.
The signal is working normally.
6.0 Make this Oxygen Sensor go lean by doing a sudden deceleration. Gently run the rpm up to about 3,000, and let the RPM drop suddenly. The fuel system should make the system go lean on deceleration. The signal should go below 0.2V.
6.1 Freeze your pattern as it goes rich and draw or photograph it onto the graph below: Note the voltage and time per division or scale next to the graph.
6.1 How low does the Oxygen sensor voltage go?0.131v
6.2 If this signal is not going low normally, describe what the signal does:
The signal is going normally.
The signal is going normally.
7.0 Measure the Response Time of the sensor. You want to know that the sensor can respond quickly to changes in the exhaust gas. The best way is to do a sudden acceleration, freeze the pattern, and measure how long it took the sensor to go from lean to rich.
7.1 Freeze your pattern as it goes suddenly rich from a lean condition and draw it into the graph below: Normally you want the voltage to go from below 0.2V to above 0.8V. in less than 100 ms. Note the voltage and time per division or scale next to the graph.
7.2 Measure how long the sensor took to go from lean to rich. Use the cursers on the scope if necessary. Record how long the sensor took here: 100ms
8.0 Discuss how a normal Zirconium oxygen sensor works: draw a picture below to help show how it works? The Zirconia oxygen sensor, measures the amount of unburnt oxygen that is in the exhaust gases and feeds this information to the ecu. The ecu uses this input to balance the fuel mixture, leaning the fuel mixture when the sensor reads rich and enriching the mixture when the sensor reads lean. Below is picture of a zirconia oxygen sensor working normally.
9.0 Discuss how good or bad this Oxygen Sensor is. What about it functions well or is faulty? Use detail and specific voltages in your discussion. Can it accurately tell the ECU how rich or lean the exhaust is? This oxygen sensor is ok because there are 6 cross-counts per 1ms which indicates the sensor isn't sluggish and is responding ok. if the number of cross-counts was slower it would indicate the sensor is getting sluggish. If it becomes sluggish it can cause hesitation problems during sudden acceleration.
Throttle Position Sensor
THEORY
The throttle position switch is operated by the throttle. It has a set of contacts for both idle and full-throttle positions. The switch signals the throttle opening to the ECU, which provides mixture correction for both idle and off idle as well as full throttle conditions. These switches became a variable resistor potentiometer type in later systems. The engine ECU using a potentiometer TPS receives an analogue voltage signal that varies with throttle position. The advantage of this design is the ECU can determine the exact position of the throttle valve at any instant and can also see the rate of the driver’s throttle application.PROCESS
In this I checked the voltage across the sensor I connected the voltmeter across the sensor the voltage was found to be 0.7V when the throttle was closed and it was 1V when the throttle was open.
REFLECTIONS
The throttle position sensor gives a reading which tells the ECU that how much fuel should be provided. The TPS gives less voltage when the throttle is closed as the throttle opens it increases the voltage. It tells the ECU how much fuel is required to be injected.
Fuel Pressure and flow
. Locate the two closest fire extinguishers. (If you have to use it remember to pull the pin, squeeze the handle, and spray at the base of the flame.) Write down where they are:
Front left of the room
2. If you can, look up Fuel Pressure specifications for the vehicle you are testing. If you can’t look them up, make a guess at the fuel specs you should have and write them down here:
38-44psi
3. Use eye protection. Optional: Relieve fuel pressure before installing pressure gauge. Or there will be some fuel that sprays at you as you attach the gauge. You can relieve pressure by several methods: 1) To relieve the fuel pressure. Make sure you have a rag to catch the fuel, start the engine. 2) Remove fuel pump (circuit opening) relay or fuse and run the engine until it stops, then crank to check that the engine doesn’t start 3) Use a vacuum gauge on the pressure regulator to lower fuel pressure, or 4) Open a fuel line at some pressure point and catch the fuel in a rag beware there may be lots of fuel.
4. Attach fuel pressure gauge and notice which scale on the gauge you will be using. Briefly turn key on or start vehicle, then turn it off. Check for fuel leaks.
Are there leaks? Yes ...................... No ✓
If there are leaks you must correct them and retest before continuing.
If there are leaks you must correct them and retest before continuing.
5. Measure the fuel pressure with the key on, engine off.
Record it here: 40psi
6. Idling: Measure the fuel pressure with the engine idling. Watch the pressure for a couple of minutes.
Record pressure here: 41psi
7. Maximum: With the engine idling, use the special tool to clamp the fuel return line. Note: this can only be done for a short period.
Record pressure here: 75psi
8. WOT: With the engine idling, disconnect and plug the vacuum linegoing to the fuel pressure regulator.
Record pressure here: 48psi
9. Residual: Turn off the engine, and watch the fuel pressure for five minutes.
Record your residual or rest pressure here: 42.5psi
10. Flow: Hook up proper equipment to read fuel volume if necessary. Record flow gauge results of volume, or how much pumped in 15 seconds: (normal results may be ½ liter in 15 seconds)
666ml
11. Replace vacuum lines. Carefully remove the fuel pressure gauge (beware of fuel spraying into eyes, avoid sparks, etc.) Turn engine key on and off, check for leaks. Start engine, check for leaks. No leaks? Check here: ✓Replace cap over fuel pressure test port. Check when done: ✓Make sure the vehicle is safe and runs fine when done, or tell your instructor.
12. Explain why it is important to know a vehicle fuel pressure/flow?
To make sure it is running at its maximum capacity
13. Describe the symptoms a vehicle would give with each case
Low fuel pressure
It will run lean , it wont idle properly. RPM will be low and it will be running rough
Low fuel flow
Blocked fuel filter , weak return vavle in pump , sping cam gets weaker it will always be richer , which means it will use alot of fuel
High fuel pressure
Too much fuel being used , dripping injectors means that there will be flooding , return regulator will be broken.
Faulty fuel pressure regulator
Floading of injectors which will leak out. The injectors causes hard starting , poor economy and useing more fuel
Camshaft Sensor
CAMSHAFT SENSOR
THEORY
As the engine management systems developed, newer processes like sequential fuel injection and variable camshaft timing was adopted. For these developments to operate the engine ECU had to calculate events on more than just crankshaft position. For sequential fuel injection the ECU had to know not only crank angle, but it had to know which if the four strokes the piston was on. Also, with the advent of variable camshaft and valve timing, the engine ECU had to be able to read the relative position of the camshaft, in relation to the crankshaft, to determine the exact dynamic cam timing. The sensors are mounted on one or more camshafts or in a camshaft-driven distributor. These sensors are usually hall effect devices, optical triggers or inductive pickup.PROCESS
In this I checked the voltage across the cam sensor. I put the voltmeter on ac volts. Then I measured the voltage at Idle rpm and at 2500 rpm. The voltage would around 0.3V at Idle and 0.5V at 2500 rpm.
REFLECTION
The voltage reading was under the spec hence the cam sensor is working properly.
Flash Codes ( Engine Check Light )
In this task we created some faults on one of the sensors and then tried to find the codes using the flash codes. The ECU would log that there is a fault with the engine. The flash code test can be done only on EFI cars not on the ones with carburettors
Flash code is a fault that is stored in the ECU and when there is a fault in a specific sensor it flashes a specific number which tells us which of the sensors have a fault. You can then bring up the code by. Turning the engine off, then turn the key to ignition then off, then switch it to ignition again, then off, then bring it to ignition again; the codes will begin to flash on the check engine light. The sequence in which the light will flash is it will flash out first number to its value.
Most of the times the fault has to be corrected by replacing the sensor but sometimes it are also due to some loose wires. The ECU can only tell which sensor has a fault but cannot tell that weather the fault is in wiring or in the sensor itself and thus diagnostics could be difficult because of this.
To clear the faults you have to remove the battery negative terminal for 30 seconds as this will clear the ECU memory. Then start the engine on and if the light does not come over then the fault has been cleared successfully.
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