AURETE001 Analyse and evaluate electrical and electronic faults in engine

management system
Report 1
Ho Yin Lam (Horace)
Group 417

1.
 Table of content

Introduction ------------------------------------------------------------------------------------- 3.
Basic inspection ------------------------------------------------------------------------------ 4.
Diagnostic --------------------------------------------------------------------------------------- 5.
Normal repairs --------------------------------------------------------------------------------- 6.
Modifications ----------------------------------------------------------------------------------- 6.
Conclusion -------------------------------------------------------------------------------------- 6.
Reference ---------------------------------------------------------------------------------------- 7.

2.
Introduction
This report is about electrical fault in engine management system. The customer
came to the workshop with the car. The customer complained about the car is having
a problem about the misfire, lack of power and engine light on. Therefore, we do a
basic inspection and diagnostic for the problem. Firstly, we talked with the customer
to get the informations as much as we can. And we did a visual inspection and scan-
ning. We found out the fault is come from the spark plug wires.

3.
Basic inspection
We should start at basic inspection. First, we need to get more information about the
problem of the vehicle. So, we need to talk to the customer and customer com-
plained lack of power.

Second, we need to do a visual inspection of the vehicle. Check all vacuum hoses
and make sure they are connected. Check all the wires in the engine compartment
and look for loose and corroded connections and damaged or burn wires. Check the
level and condition of the engine coolant. Check the level and condition of the trans-
mission fluid. Check the air filter and check the air intake system for restrictions and
leaks.Also, we can check the available service information that may relate to the
symptom. After that, we can use the scanner to check if there is a trouble code.

The outcome that come from the scanner is P0300. That is the random misfire code
which means the engine is misfiring, but the problem is not isolated to one or two
cylinders. It is jumping around from the cylinder to another cylinder. A random misfire
code usually means that the mixture of the air and fuel is running lean. There can be
many reasons of that problem for example, vacuum leak, dirty fuel injectors, low fuel
pressure, weak ignition coil, bad plug wires or compression problems.

4.
Diagnostic
Vacuum pressure test
The first thing we need to check is the intake vacuum with a vacuum pressure
gauge. First we start the car and let the vehicle idle for few minutes. Then put the
gauge on the hose, test the hose to see of they hold the pressure, the result should
be stable and can not be under 50 PSI.
Fuel injectors test
Turn the ignition on and connect the test light to the negative of the battery. Then, lo-
cate the two wires that go into each injector. The injectors should be continuously re-
ceiving the power from the electrical system of the vehicle. Therefore, we test each
wire for the voltage. If both wire do not make the test light turn on, then there is an is-
sue with the power reaching the fuel injector.
Fuel pressure test
Start the car and let it idle. Install the fuel pressure gauge and run the pump, then
note down the pressure reading. Compare the result to the manufacturer specifica-
tion. If the pressure is lower than the specification, that means the problem might
come from the fuel pump.
Ignition coil test
First remove the connector from the ignition coil and measure the voltage of the 2 pin
that inside the connector. Switch on the ignition. Then connect the multimeter to the
ground of the engine and test the ignition coil. The voltage should be around 12V.
Compression test
Remove the fuel pump and fuel injection fuses. Then disconnect the main wire to the
coil and spark plug wires and remove the spark plug. Install the compression gauge
in to the spark plug hole. Then turn the ignition on, depress the throttle and crank the
engine four or five revolutions. The result reading should be stable. And do the same
with all the cylinders.

Spark plug wires test

We have found a physical damage from the wires at the visual inspection. So, now
we need to check the resistance of the wires by using the digital multimeter. First we
remove the wire from the engine. Then set the multimeter to Ohms. Attach the meter
probe on each end of the cable and read the total resistance should be 12,000 ohms
for each foot. After that, hold the test light to an engine ground. When the engine
running, move the test light along the length of each spark plug wire. And there has a
spark jumps from one of the plug wire. That means the insulation of the plug wire
has broken down, and the spark plug wire should be replaced. The reason of that is
the engine heat from the engine that burn the wire insulation and boots.

5.
Normal repairs
For that problem, we just simply replace all the spark plug wires, not only the faulty
one, because the other wires might occur the same problem again. It is important to
install the spark plug wires in order.

Modifications

For the modifications, because the spark plug leads are burned by the engine heat,
to avoid this problem we need to buy a wire that is heatproof to protect the wire. For
the price we need to do it as cheap as we can, because the customer does not want
to pay to much for just a wire. So, we buy the wire that is from the aftermarket. To
follow the Australian design rules we need to find the wire that is same to the manu-
facturer. And the material of the wire should be sustainable for the environment.

Conclusion

We did a modifications for the customer that is about the spark plug wires. The rea-
son of the faulty spark plug is that the wire was burned by the engine heat,
because the wires are made of rubber. Therefore, we changed the wire to the one
that with heat proof to avoid the heat problem.

6.
Reference

http://www.autotap.com/problem6_engine_stalls.asp
http://www.crankshift.com/spark-plug-wires/
https://shop.advanceautoparts.com/r/car-projects/how-to-replace-spark-plug-
wires

7.