The above diagram illistrates how the fuel is pumped to the injectors. The fuel in the fuel tank, gets pumped up by a fuel pump. As the fuel pump operates, it creates a spark, but as it is always emerged in fuel, it cannot ignite. It is the vapour of the fuel that is inflammable, not the actual fuel itself. This is why we should never run the car on a empty tank, or bench test the fuel pump. The fuel is then transfered to a fuel filter, which collects all the dirt and grime out of the fuel. These filters should be replaced every 30,000km. The fuel then travels to the injectors where it gets sprayed into the combustion chamber. Any fuel left over gets recycled, and goes down the return line and back into the fuel tank. The fuel pressure regulator maintains the fuel pressure at around 32-38 psi. With the engine at idle, the vacuum is around 20 Hg, the fuel pressure is approx 32. psi. At WOT (wide open throttle) the vacuum drops to 0 Hg, the fuel pressure then increases to 38 psi.
Voltage to injectors with the car idling.
Cylinder1 Cylinder 2 Cylinder 3 Cylinder4
14.12V 14.02V 14.03V 14.18V
Checking with LED test light on each cylinder (did the LED flash?)
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
Yes Yes Yes Yes
With multimeter on duty cycle %
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
0.3% 0.1% 0.1% 0.4%
Accelerate the engine with short fast bursts and measure the % (duty cycle)
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
18% 24% 19% 24%
Set Multimeter to Hz with car idling and measure frequency
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
6.0 6.0 5.9 6.0
Accelerate the engine and measure Hz
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
11.7 17 21 20.6
Using the formula calculate the pulse width of each injector
IDLE
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
0.3x100/6 = 5pwm 0.2x100/6 = 3.3pwm 0.2x100/5.9 =3.3pwm 0.4x100/6 = 6.6pwm
REVVED UP
Cylinder 1 Cylinder 2 Cylinder 3 Cylinder 4
18x100/6 = 300 pwm 24x100/6 = 400 pwm 19x100/5.9 = 322 pwm 24x100/6 = 400 pwm
WS2 FLASH CODES
Make: Toyota Model: Corolla Year: 2001
In order to test the vehicle flash codes, we used a jumper wire that connected from TE1 to E1 on the diagnosis box under the hood. We found out how to check for flash codes by reading the Toyota Service Manual.
After we connected the jumper wire properly, we checked for the flash code on the dash board. We got code 12 which was a G,NE Signal circuit, which we got from disconnecting the distributor. We also got codes 22 and 31 which was the Water Temperature Circuit, and the Vacuum Sensor Circuit.
After we noted all the faults we checked under the hood to do a visual inspection of the parts. We noticed the distributor was fine, so asked our lecturer why we were getting a fault, and he explained that because we had previously disconnected the distributor the ECU had stored the fault in the system. We then checked the Water Temperature Sensor and MAP sensor and noticed they were both unplugged. We then connected the sensors, then disconnected the battery for 30 seconds to clear the faults in memory. We then rececked the faults, and the ECU gave us an all clear message by flashing on and off in quick succsecion.
These faults could have affected engine performance from the ECU having no idea what the engine temperature was. The engine could run too hot, damaging the parts inside. The vacuum sensor would not tell the ECU how much load was on the engine, so the ECU wouldn't be able to advance the spark when accelerating.
Other tests that could be carried out to test the sensors could be to check the voltage output with the specs of that type of sensor. When the fault code comes up, it's not always the sensor that is the problem, there could be a short in the circuit, or an open circuit. An ohmmeter could be used to checked for these faults in the circuits.
WS3 OSCILLOSCOPE PATTERNS
Make: Toyota Model: Corolla Year: 2001
Signal name: MAP, analogue
Volt division range: 1
Time division range: 2ms
We measured the MAP sensor output voltage wire with the key on, engine off. And got a reading of 3.6V. We checked the Toyota service manual and our specifications said it should be around 3.6V at sea level. So we knew the MAP sensor was good. We then started the car at idle and put the oscilloscope on the MAP sensor, and measured a constant 1.17V. We also tested the 5V reference wire and got 4.56V.
Signal Name: TPS
Volt Division/Range: 1
Time Division:100 ms
We tested the TPS Sensor output voltage with the key on engine off, and got 0.5V as you can see at point A on the graph. We then slowly opened the throttle, and got 1.32V. We then measured the voltage with Wide Open Throttle, and got 4.78V. We checked the specifications of the Toyota Service Manual. The specs for this TPS should be 0.5V or lower so my idle spec is good. The spec for WOT is 3.5-5.5V so my TPS sensor is in good condition. We also tested the TPS by slowly opening the throttle and checking the oscilloscope for any jumps on the carbon track when we adjusted the throttle, but the oscilloscope gave us a good smooth voltage rise so we knew the carbon track on the
TPS sensor was good.
Signal: Injector
Volt division range: 20V
Time division range: 10ms
B shows the ECU grounding of the solenoid, which opens the injector. This amount of time is called PWM.
C shows a voltage spike occours called back EMF from the ECU removing the earth and closing the injector.
D The voltage has returned back to charging voltage, and the whole process will start again.
Signal: Primary Ignition
Volt range: 20v
Time/division range: 10ms
B shows the ECU grounding the coil. This is the amount of time the coil is charging and is referred to as dwell time. In ignistion systems with a ballast resistor, there will be a little rise in voltage called a current limiting hump. This is to prevent the coil from overheating from too much current.
C shows a voltage spike or (back emf) from the ECU removing the earth. This will collapse the magnetic field and induce a current into the secondary coil, which creates the spark, (but as this is only a graph of the primary coil, we cant see this happen)
D shows the voltage returning back to charging voltage.
Signal: NE CKP Mag distributor
Volt division range: 2V
Time division range: 50 ms
A shows an increase of voltage. This is the charging time of the coil, or the (dwell time). This is from the reluctor wheel spinning creating a magnetic field by moving closer to the pickup coil.
B shows the reluctor wheel at the point where the reluctor tip has the smallest gap between the pickup. This creates full saturation of the pickup coil and makes the voltage increase at a drastic rate.
C shows the voltage drop suddenly from the reluctor tip moving away from the pickup coil.
D shows the voltage increasing from the reluctor wheel rotating towards the coil again, and process A is repeated.
Signal: IGF
Volt range: 2V
Time Division: 20ms
We then started the engine with the connecter still disconnected and measured IGT and Earth this time and recorded around 4V. We checked the specifications again and the specs said the voltage sohuld be between 0.1V and 4.5V.
In conclusion our IGF and IGT circuits were good and putting out the correct amount of voltage.
Signal: G Pick up Coil on Distributor
VPD: 1V
TPD: 50 ms
