TTEC 4826– Engine Electronic Control Systems Off Car

Testing a throttle position sensor (TPS)

The first TPS i tested was a potentiometer.

The TPS is used to monitor the position of the throttle in an engine.It is located on the throttle body. This effects the ignition timing and fuel injection timing.This TPS works by providing a variable resistance depending upon the position of the throttle. Resistance is in decreased in this case as more throttle is applied. It is a normally closed circuit. The voltage changes to tell the ECU or PCM when the driver is requiring more power or less power depending on throttle positioning. These sensors are adjusted by adjusting the mounting screws.


Throttle Angle Voltage

WOT = 3.9V

1/4 Throttle= 1.3V

1/2 Throttle= 2.3V

3/4 Throttle= 2.92V


Testing the throttle position switch (TPS)
PSW means power switch (WOT)
IDL means idle circuit

PSW

WOT= 0 ohms
Idle=0L

IDLE

Idle=0 Ohms
WOT= OL

The resistance changes beacuse the circuit is normally closed reading 0L and when it is switched and an open circuit it then reads 0 Ohms in both cases. the PSW circuit is only working under throttle (0 ohms) and is off (0L) during idle. The idle circuit only works at idle (0 ohms) and is off (0L) at throttle. The difference between the resistances means (0L is OFF) (0 ohms is ON). I am unsure if this throttle position sensor meets the manufacturers requirements because i dont know what kind of car this TPS was off.

Testing a MAP sensor
(Manifold Absolute Pressure)

The map sensor i tested decreased in voltage as more pressure was applied.
0 inches of mercury = 3.6V
19 inches of mercury= 1.9V
23 inches of mercury=1.4V
26 inches of mercury=1.2V
27 inches of mercury=1.2V

The map sensor is used to calculate the volume of air entering the engine and the amount. This is calculated by pressure inside the intake manifold. Most EFI systems use ethier a MAP sensor or a AFM but some use both. The map sensor then sends the signal to the ECU and the ECU delivers the correct amount of fuel. AFR (air fuel ratio). The map sensor reads pressure. when the engine is running vacuum is created inside the manifold by the movement of the pistons and the restriction created by the throttle plate. At wide open throttle vacuum drops to almost zero and pressure inside the intake manifold once again nearly equals the outside pressure. The MAP sensor is a pressure transducer which is an electrical device with a 2 chambers and a diaphragm in the middle. It detects the amount off vacuum created from the engine in one chamber and another chamber is a sealed chamber and the pressure of this chamber is calibrated to give the ECU constant measurements. This difference in pressure causes the diaphragm to bend one way or the other. The degree of deflection is measured by the strain gage and that data is relayed to the ECU.I am unsure if it meets manufactures specifications because i dont know what car it was off.

Testing a AFM (Air flow meter)
Hot wire sensor (AFM)

These sensor work by heating a wire with an electric current that is suspended in the engine’s air stream. The wire's resistance increases as the wire’s temperature increases, which limits current flowing through the circuit. When air flows past the wire, the wire cools, decreasing its resistance, which allows more current to flow through the circuit. As more current flows the wire’s temperature increases until the resistance is the same size as before ( X ohms). The amount of current required to maintain the wire’s temperature is directly proportional to the mass of air flowing past the wire. The integrated circuit converts the measurement of current into a voltage signal which is sent to the ECU.

A mass air flow sensor is used to find out the of air entering an engine. This is nessicery for the ECU to deliver the correct AFR (air fuel ratio). These sensors usually run on 5V.

The air flow meter i tested read 1V when wired up under test conditions with no air.

The voltage gradually increased as i blew through it indicating it is working correctly.

Advantages over older vane type.

responds very quickly to changes in air flow
low airflow restriction
smaller overall package
less sensitive to mounting location and orientation
no moving parts improve its durability
less expensive
separate temperature and pressure sensors are not required (to determine air volume).

Disadvantages

Hot wire can get dirty and will affects the engine operation.

Vane type Air flow meter

The vane type i tested was a BP26-13-21C

Closed throttle 4.2V
1/4 throttle 2.3V
1/2 throttle 1.9V
3/4 1.8V
WOT 1.7V

A vane, or paddle, projects into the engine’s intake air stream on a spring-loaded arm. The vane moves in proportion to the airflow, and a voltage is generated in proportion to the distance the vane moves, or the movement of the vane directly regulates the amount of fuel injected, as in the K jetronic system.

The vane moves because of the force of the air flow against it. The force depends on air density, speed and the shape of the vane.

Vane Type Disadvantages

• it restricts airflow which limits engine potential
  




• moving electrical or mechanical contacts wear out.
  




• finding a suitable mounting location as it as quite large.
  




• the vane has to be mounted with respect to gravity

Engine Coolant Temperature sensor


Room temperature: 2200 Ohms
30 Degrees:1800 ohms
40 Degrees:1300 Ohms
50 Degrees:1100 Ohms
60 Degrees:610 Ohms
70 Degrees:500 Ohms
80 Degrees:360 Ohms

Inside the sensor is found what is called a thermistor. This is an electronic temperature sensitive variable-resistor. The ECT is a negative temperature coefficient sensor. This means that as temperature goes up resistance and voltage goes down or vise-versa. The ECT sensor receives a 5.00 volts reference voltage from the ECU. The ECT works by changing its internal resistance according to coolant temperature and therefore also changing the voltage drop across the ECT.

Thermo fan switch



20 Degrees=0.7K ohms
30 Degrees=0.692K ohms
40 Degrees =0.580K ohms
50 Degrees=0.46K ohms
60 Degrees=0.35K ohms
70 Degrees=0.28K ohms
80 Degrees=0.22K ohms.

I am unsure if it meets manufacturers specifications because i dont know what car this thermo fan switch is off. A thermistor is a type of resistor whose resistance changes greatly with temperature. The above reading show that this is a thermistor. The resistance changes because that is how a thermistor operates. It works by turning the fan on when X amount of ohms is reached i am unsure of the exact number in this situation. This is a NTC thermistor. (Negative temperature coefficient)

Air Temperature Sensor




Room Temperature: 2480 Ohms
30 Degrees:1300 Ohms
45 Degrees:1100 Ohms
50 Degrees:1000 Ohms
75 Degrees:914 Ohms
80 Degrees:700 Ohms.

I am unsure if it meets manufactures specifications because i am unsure what car this sensor came off. It seems to be in working condition as the resistance is dropping when temperature is increased. This is a negative temperature coefficient thermistor as it decreases resistance with heat. This sensor and the engine coolant temperature sensor at 80 Degrees both were around 300 ohms. They are both temperature coefficient thermistors.

Optical Distributer

Points A,B,C.

At point B This is when the device is "on" When the chopper blade is not blocking the light.

At point A This is when the device is"off" When the chopper blade is blocking the light

At point C This is when the device is "on" again When the chopper blade is not blocking the light.

The differences between hallf effect, optical and inductive signals are inductive signals are magnetic these are signwaves and are AC voltage.This signal increases voltage and amplitude with frequency. Hall effect and optical are square waves and are ether on or off. These are more accurate than inductive because amplitude and voltage dont increase with frequency. Hall effect starts "off" and switches "on". Optical starts "on" and switchs "off".

The cams spin at half the speed of the crank. So the distributer must spin at half the speed of the crankshaft. So when the distributer turns 360 degrees the crank turns 720 degrees. If it is a 4 cylinder car the distributer will fire every 90 degrees. 6 Cylinder 60 Degrees. 8 Cylinder 45 Degrees.

Knock Sensor

Waveform is from Google images as the digital oscilloscope wasn't able to give a correct waveform because the divisions wouldn't go low enough.

The knock sensor allows the engine to run at the most advance timing possible before detonation. It advances the timing until knock is detected, A voltage is created so the timing retards. The ECU leaves the timing at right before the knocking point for optimum power and fuel economy. They create voltage because they are piezoelectric crystals.

Injector Testing.

We only had 2 injectors available to test the results were:

Injector 1
Manufacturers specifications: 14-17 Ohms
Measured at:15.5 ohms
Earth leakage test= 0L

Injector 2
Manufacturers specifications: 14-17 Ohms
Measured at: 14.0 Ohms
Earth leakage test=0L.

Heard both injectors click.

Other problems that could give the same result as an injector not firing:

Anything air, fuel or spark related will cause misfire if there is a problem within any of the systems.

Test Bench Cleaning

When removing fuel injectors the safety procautions are wear correct safety gear including overalls, eye protection. Use a fuel injector puller if you have one to avoid damaging expensive components. Dont lose the clip.

Dont know manufacturers specifications because i dont know what car they came off.
We measured a flow rate of 45ml /45cc for 60 seconds With 0 Drips.
2700ML a hour.

Out of the 4 injectors we tested 3 worked and 1 had a damaged plug so it worked intermitantly. Apart from the plug all injectors had a good spray pattern and worked well. These injectors would be fine to use again in the appropriate vechile.

Testing Ignition Coils

Coil one:
Part No. 16C6.
Voltage 6V
Primary resistance= 2.1 ohms. ( Measured)
Secondary resistance=7.5K ohms. (Measured)

Coil two:
Part No. F-088
Voltage 12V
Primary resistance 0.9 Ohms (Measured)
Secondary resistance 12.57K ohms (Measured)

Wasted Spark.

Coil primary
1= 0.7 Ohms
2=0.8 Ohms
3=0.6 Ohms

Coil secondary
1=12.2K ohms
2=12.3K ohms
3=12.3K ohms

Testing Ballast resistors
Part no: BR1
Resistance= 1.2 Ohms.

Standard Single tower coil


1. Wire up a ballast resistor in series with your coil primary winding values as shown in
the following diagram.
2. Connect an ammeter in series and note the current draw.
3. Measure and note the voltage drop across the ballast resistor.
4. Measure and note the voltage drop across the coil primary.

Current draw was 3.1A
Coil calculated voltage drop=6.51V
Coil measured voltage drop=10.6V
Ballast resistor calculated voltage drop=3.72
Ballast resistor measured voltage drop=1.3V

Wire up an ignition module using a function generator to trigger the module.
Have a coil and spark plug in the circuit so the spark plug can fire
Check with your tutor that you have done it correctly
Draw a wiring diagram of how you wired the circuit

Wire up an ignition module using a distributor to trigger the module.
Have a coil and spark plug in the circuit so the spark plug can fire
Check with your tutor that you have done it correctly
Draw a wiring diagram of how you wired the circuit




Wire up the wasted spark ignition system using the function generator to trigger the
modules.
Have the coils and sparks plug in the circuit so the spark plugs can fire.
Check with your tutor that you have done it correctly.
Draw a wiring diagram of how you wired the circuit


Wire up the coil over ignition system using the function generator to trigger the module
Have the coil and spark plug in the circuit so the spark plug can fire
Check with your tutor that you have done it correctly
Draw a wiring diagram of how you wired the circuit

Build the ignition circuit below on a breadboard using two 2N2222 transistors (or
equivalent)
Find the maximum current value of the transistors from the data sheet, the resistance of
the coil. Then calculate the resistor need to protect the circuit. Show calculations:

100mA maximum current from transistor.
2.1 Ohms
=12/0.1 = 120 Ohms.

The difficulty's i encountered were the circuit didn't work with the resistor in it i think this is because the diagram above has been drawn incorrectly.If i was going to build it again i wouldn't use a resistor