ENGINE MANAGEMENT SYSTEM
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DO: Ignition secondary leads should not be
routed with the ignition primary harness or any
other electrical harness.
Voltage spikes can be transmitted from the
secondary cables into other leads which are in
close. This could create a component
performance degradation or failure condition
DO: Spark plug wires(secondary leads) & primary
wiring:
- must not contact sharp surface
- must not be under tension between fixed points
- must be clear of moving parts (belts, fan, etc…)
- must be protected from or kept at least 125 mm
away from radiant heat source exceeding 400 F.
- must be protected from environmental damage
(dirt, splash, oils, fluids, etc….)
- must be retained, secured or insulated to
prevent pinching, mis-routing, rattles, and
squeaks
- Spark plug wires carry very high voltage
(30,000 volt). If the secondary lead loses its
dielectric characteristics thru being nicked, cut ,
chaffed, then an arc thru to a near by ground
could take place. This kind of condition could
lead to misfire, no start, or premature failure of
ignition system.
DO: Not all fasteners are designed for repeat use.
Beware of fastener specifications. All harnesses
should be supported within 6" of a mating
connection.
Adequate retention force might not be achieved
if the fastener is not designed to be reused.
Mating connections are not designed to support
the weight of the harness assembly.
DO: For removing spark plugs follow the following
steps:
1- Grasp the spark plug boot and gently
2- rotate 90; and then pull the spark plug boot
and cable away from the spark plug
3- Before removing spark plug, brush or air blast
dirt away from the well areas
4- Use correct size deep socket wrench to
loosen each spark plug one or two turns
To remove spark plugs from Aluminum heads,
allow the engine to cool. The heat of the engine,
in combination with a spark plug that is still hot,
may cause the spark plug threads to strip the
cylinder head upon removal
Use goggles to protect eyes from dirt when
applying compressed air to spark plug wells
DO: Cleaning a spark plug could be done as
follow:
1- wipe all spark plug surfaces clean….remove
oil, water, dirt and moist residues.
2- If the firing end of spark plug has oily or wet
deposit, brush the spark plug in an approved,
non-flammable and non-toxic solvent. Then
dry the spark plug thoroughly with
compressed air
3- Use a propane torch to dry wet-fuel fouled
plugs. Allow the torch flame to enter up the
center electrode insulator. Allow plug to cool
down
4- If the spark plug threads have carbon & scale
deposits, clean with wire brush, taking care
-Cleaning a spark plug will reduce the voltage
required for an electrical arc(spark) across the
electrodes
-Cleaning & re-gapping will not restore a used
spark plug to a new condition. It may be more
economical and efficient to replace used spark
plugs with new plugs instead of cleaning.
-Sooted plugs should be replaced
-Do not cool by using water or any liquid
-Clean threads permit easier installation and
proper seating which will maximize transfer heat
away from the plug
ENGINE MANAGEMENT SYSTEM
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not to injure the electrode or the
insulator tip
DO: Regap spark plugs to the exact
measurement specified by the engine
-Too wide a gap could cause the plug to
misfire(higher required ignition voltage).
manufacturer to keep the best fuel economy and
proper engine performance
- Use round wire-type gauge for an accurate
measure of gap on all used spark plugs
- when gapping a spark plug only the side
electrode is moved. The center electrode must
not be moved
-Too narrow of a gap could affect idle stability
-A flat gauge can’t accurately measure the spark
plug on used plugs
DO: When replacing spark plugs with new ones,
always use equivalent plugs with same heat
range, thread, size, etc….
-Higher heat range plug(hotter plug) could lead
to pre-ignition & possible piston damage
-Lower heat range (colder plug) could lead to
cold fouling & emission problem
DO: For installing spark plugs follow the following
steps:
1- make sure the cylinder head threads and
spark plug threads are clean. Make sure the
spark plug thread is free of dings and burrs. If
necessary, use a thread chaser and seat
cleaning tool.
2- Make sure the spark plug gasket seat is
clean, then thread the gasket to fit flush
against the gasket seat. Tapered seat plugs
do not require gaskets
3- Screw the spark plugs finger-tight into the
cylinder head. Then, use a torque wrench to
tighten spark plugs following manufacturer’s
recommendation).
Torque is different for various plug type & cylinder
head material
-If the thread is damage, it prevents a good heat
transform from the shell to the cylinder head
-Do not use any type of anti-seize compound on
spark plug threads. Doing this will decrease the
amount of friction between the threads. The
result of the lowered friction is that when the
spark plug is torqued to the proper specification,
the spark plug is turned too far into the cylinder
head. This increases the likelihood of pulling or
stripping the threads in the cylinder head
-Over-tightening of a spark plug can cause
stretching of the spark plug shell and could
allow blowby to pass thru the gasket seal
between the shell and insulator. Over-tightening
also results in extremely difficult removal
Fuel Pump Module
1．Description and Working Principle
Fuel Pump Module supplies fuel to engine at system pressure. Fuel Pump Module is
mounted to fuel tank at bottom and supplies fuel to engine through hoses.
Fuel Pump module consists of Fuel Pump to generate the fuel flow and pressure regulator to
regulate the fuel pressure.
Fuel Pump
When power is supplied to fuel pump, motor in pump assembly rotates the impeller. Impeller in
turn draws the fuel from strainer and pumps the flow to generate the system pressure.
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