Download - Ignition Fuel Pump and Spark Plug
-
8/12/2019 Ignition Fuel Pump and Spark Plug
1/62
IGNITION SYSTEM-SI ENGINE
the ultimate spark creator in petrol
engine.
UNIT-2
EME-505 I.C.ENGINES
B.TECH 5TH SEM MECHANICAL ENGINEERING
2011 batchBY
VINOD KUMAR YADAV
MECHANICAL ENGG. DEPTT
G.L.B.I.T.M
-
8/12/2019 Ignition Fuel Pump and Spark Plug
2/62
BASICS OF IGNITION SYSTEM
SI enginelow compression ratio and high self ignition temperatureof fuelso for combustion ignition source is must.
Principle:A conventional ignition system should provide sufficientlylarge voltage across the spark plug electrodes to affect the sparkdischarge.
Air is poor conductor of electricity- an air gap in an electric circuitacts as a high resistance. But when a high voltage is applied acrossthe electrodes of a spark plug, it produces a spark across the gap.
When such a spark is produced to ignite a homogeneous A/Fmixture in the combustion chamber of an engine it is called thespark ignition engine (or SI Engine).
-
8/12/2019 Ignition Fuel Pump and Spark Plug
3/62
BASIC REQUIREMENT OF IDEAL IGNITION SYSTEM
Supply necessary energy within a small volume in a time sufficiently
short to ensure that minimum energy is lost other than that neededto establish the flame under all conditions of operation.
For A/F range 12-13:1 a spark under 10 millijoules is sufficient to
initiate the combustion.
The system must produce and distribute high voltage of the order of
20000 volts to 22000 volts for generating spark between theelectrode gap
The system must have a source of electrical energy (may be a
battery or a generator or a magneto).
Battery voltage is usually 6 to 12 volts. This low voltage is boosted
by means of an induction coil, contact breaker and a condenser to avalue sufficient to meet the breakdown voltage and to release
sufficient energy for spark generation.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
4/62
TYPES OF IGNITION SYSTEM
1. Battery Ignition system(conventional and transistor assisted)
2. Magneto ignition system
3. Electronic ignition system
-
8/12/2019 Ignition Fuel Pump and Spark Plug
5/62
-
8/12/2019 Ignition Fuel Pump and Spark Plug
6/62
BASICS OF BATTERY IGNITION SYSTEM
Distributor form the secondary circuit
COMPONENTS OF THE IGNITION SYSTEM
-
8/12/2019 Ignition Fuel Pump and Spark Plug
7/62
1- A Ballast resistor: In series with primary winding to regulate
primary current. The objective of BR is to prevent injury to the sparkcoil by overheating if the engine should be operated for a long time
at low speed, or stalled with breaker in closed position.
This coil is made of iron wire, and iron has the property that its
electrical resistance increases very rapidly if a certaintemperature is exceeded.
The coil is therefore made of wire of such size that if the
primary current flows nearly continuously, the ballast coil
reaches a temperature above that where this rapid increase in
resistance occurs. This additional resistance in primary circuit
holds the primary current down to safe value.
For starting this resistor is by passed so that more current can
flow in the primary circuit.
COMPONENTS OF THE IGNITION SYSTEM
-
8/12/2019 Ignition Fuel Pump and Spark Plug
8/62
2-A cam rotating at camshaft speed operates the contact
breaker points and causes them to open and close.
3- Ignition coil to step up the 6 volts or 12 volts of the
battery to a high tension voltage sufficient to promote
and electric spark across the electrodes of the spark
plug.
4- A distributor to distribute the high voltage to different
spark plugs at correct time
5- A battery : 6 volts or 12 volts (Lead acid light duty
commercial vehicles : Alkaline battery heavy dutycommercial vehicles)
6- Contact breaker points (CB point) : Made of hard
material (tungsten) with 3 mm diameter.
COMPONENTS OF BATTTERY IGNITION SYSTEM
-
8/12/2019 Ignition Fuel Pump and Spark Plug
9/62
CONSTRUCTION OF IGNITION COIL
-
8/12/2019 Ignition Fuel Pump and Spark Plug
10/62
IGNITION COIL CONSTRUCTIONAL DETAILS
The Ignition coil consist of two insulated conducting coil-
primary and secondary.
The primary winding is connected to the battery through an
ignition switch and the contact breaker.
The secondary winding is connected to the spark plugs
through the distributor
In order to boost the voltage the primary windings has a few
hundred turns (100-300) of relatively thick wire (20 gauge)
while the secondary windings contain several thousand turns
(20000-22000) of thin wire (38-40 gauge enameled copper wire
sufficiently insulated to withstand high voltage). More heat is
generated in primary than secondary and so primary windingis wounded over secondary to dissipate heat.
The two wires are also interconnected allowing the secondary
windings to be earthed through the primary circuit
-
8/12/2019 Ignition Fuel Pump and Spark Plug
11/62
Ignition coil contd.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
12/62
WORKING OF BATTERY IGNITION SYSTEM
When ignition switch closed (switch on) primary winding is
connected to positive terminal post of storage battery. If
primary circuit is closed through the CB point, a current flows
which is called primary current
Primary current produces a magnetic field in core.
A cam driven CB opening mechanism opens it when spark is
required
When CB points are open, the current which had been flowing
now flows into the condenser.
As the condenser becomes charged, the primary current falls
and magnetic field collapses.
The collapse of the field induces a voltage in the primarywinding, which charge the condenser to a voltage much higher
than the battery voltage.
The condenser then discharges into the battery, reversing the
direction of both the primary current and the magnetic field.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
13/62
WORKING OF BATTERY IGNITION SYSTEM
The rapid collapse and reversal of the magnetic field in the core
induce a very high voltage in the secondary winding.
The secondary winding consists of large number of turns of
very fine wire wound on the same core with the primary.
The high secondary voltage is led to the proper spark plug by
means of rotating switch (distributor).
-
8/12/2019 Ignition Fuel Pump and Spark Plug
14/62
2-MAGNETO IGNITION SYSTEM
-
8/12/2019 Ignition Fuel Pump and Spark Plug
15/62
2-MAGNETO IGNITION SYSTEM WORKING
Magneto- special type of electric generator
It is mounted on the engine and replaces all the components
of the coil ignition system except the spark plug and cb point
- A magneto when rotated by the engine, is capable of
producing very high voltage and does not need a battery
as a source of external energy
- The high tension magneto incorporates in itselfwindings to generate as well as to step up the voltage
and thus does not require a separate coil to boost up
the voltage required to generate the spark.
- Magneto can be rotating armature type or rotating
magneto type- The operation of the magneto ignition system is exactly
same as that of the battery coil ignition system. In MIS
as the breaker points are opened and closed with the
help of a cam, the primary circuit flux is charged and
a high voltage is produced in the secondary
circuit
-
8/12/2019 Ignition Fuel Pump and Spark Plug
16/62
Magneto Vs Battery Ignition systemS.No Battery Ignition system Magneto Ignition system
1 Requires battery: Difficult to
start the engine when battery is
discharged
No battery, no discharge
2 More maintenance problems
due to battery
Less maintenance
3 Current for primary circuit isobtained from battery
Current is generated by magneto
4 A good spark is available at spark
plug even at low engine speed.
During starting quality of spark is
poor due to low speed.
5 Efficiency of system decreases
with reduction in spark intensity
as engine speed rises.
Efficiency of system increases with
increase in engine speed due to
high intensity spark
6 Occupies more space Occupies less space
7 Used in cars and LCVs Used in Racing cars and two
wheelers
-
8/12/2019 Ignition Fuel Pump and Spark Plug
17/62
LIMITATIONS OF BREAKER SYSTEMS
AND NEED OF MODERN IGNITION
SYSTEMS Contact Breaker systems: Available voltage decreases
as engine speed increases due to limitations in current
switching capability of the breaker system and the
decreasing time available to build up the stored energy
in the primary coil.
Due to high current load, the breaker points are
subjected to electrical wear in addition to
mechanical wear which requires frequent
maintenance
So there is a need to develop advanced (Modern)
ignition systems (like TCI and CDI)
-
8/12/2019 Ignition Fuel Pump and Spark Plug
18/62
TRANSISTORISED IGNITION SYSTEM
OR
TRANSISTOR ASSISTED CONTACT SYSTEM (TAC)
-
8/12/2019 Ignition Fuel Pump and Spark Plug
19/62
TRANSISTOR ASSISTED CONTACT SYSTEM (TAC)
The inherent property of transistor is to interrupt a relatively high current
carrying circuit, i.e its ability to control a much larger current in the collector
circuit with a small current in the base circuit, makes it ideal replacement forthe breaker points and condenser of a conventional ignition system.
The emitter (E) of the transistor is connected to the ignition coil through a
ballast resistor and the collector (C) to the battery. When the cam operated
contact point opens the base current and , thereby, the primary circuit current
is interrupted and the normal induction coil operation follows.
The current through the contact breaker is reduced by a large amount due tothe fact that the contact breaker has to switch only the base current
TRANSISTOR ASSISTED CONTACT SYSTEM (TAC)
-
8/12/2019 Ignition Fuel Pump and Spark Plug
20/62
TRANSISTOR ASSISTED CONTACT SYSTEM (TAC)
disadvantages
Source impedance: Opposition exhibited by output terminals to an AC of a
particular frequency as a result of resistance, inductance and capacitance
-
8/12/2019 Ignition Fuel Pump and Spark Plug
21/62
4-HIGH VOLTAGE CAPACITIVE DISCHARGE IGNITION
OR
CAPACITIVE DISCHARGE IGNITION (CDI)
In CDI ignition system, a capacitor is used as a means of energy storage. It
is charged to a high voltage (about 500volts) by means of a transformer and
at the moment of ignition, discharged by the thyristor through the primary
circuit which generates a high voltage pulse in the secondary circuit to fire
the spark plug
CDI Trigger box contains Capacitor, thyristor power switch (SCR), charging
device (to Convert battery voltage to the charging voltage of 300 to 500 V by
means of pulse Via a voltage transformer
-
8/12/2019 Ignition Fuel Pump and Spark Plug
22/62
Further explanation onTransistorized
Ignition System
-
8/12/2019 Ignition Fuel Pump and Spark Plug
23/62
Transistorized Ignition System In automotive applications, the transistor ized
coi l ign i tion sys tems which prov ide a higheroutpu t vo l tage and use electronic triggering tomaintain the required timing are fast replacing theconventional ignition systems. These systems are
also cal led high energy electronic igni t ionsys tems.These have the following advantages:-
1. Reduced ignition system maintenance
2. Reduced wear of the components.
3. Increased reliability4. Extended spark plug life
5. Improved ignition of lean mixtures
-
8/12/2019 Ignition Fuel Pump and Spark Plug
24/62
An ignition system using a transistor as a power switch; available as
breaker-triggered TI with contact breaker or as breakerless TI with
magnetic pick-up or hall generator.
This type of maintenance-free electronic ignition system constantly
feeds electrical power to the high tension coil(s) [also known as ignition
coil(s)]. The circuit is switched on and off by a transistor circuit in the
ECU or igniter assembly. This system is commonly found on
motorcycles using fuel injection. The longer spark duration, a feature of
this system, makes it a good choice for improving the fuel combustion
and thereby lowering the exhaust gas emissions.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
25/62
-
8/12/2019 Ignition Fuel Pump and Spark Plug
26/62
CDI SYSTEM WORKING
Capacitor discharge ignition (CDI) or thyristor ignition is atype of automotive electronic ignition system which is widelyused in motorcycles, lawn mowers, chain saws, small engines,turbine powered aircraft, and some cars.
It was originally developed to overcome the long chargingtimes associated with high inductance coils used in inductiveignition systems, making the ignition system more suitable forhigh engine speeds (for small engines, racing engines androtary piston engines).
Capacitor discharge ignition uses capacitor discharge currentoutput to fire the spark plugs.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
27/62
ADVANTAGES OF CDI SYSTEM OVER TCI SYSTEM
-
8/12/2019 Ignition Fuel Pump and Spark Plug
28/62
Further explanation on
C.D.I.
(Capacitive Discharge
Ignition System)
-
8/12/2019 Ignition Fuel Pump and Spark Plug
29/62
Capacito r dis charge ign i t ion (CDI)or thyr istor igni t ionisa type of automotive electronic ignition system which iswidely used in motorc ycles, lawn mowers, chain saws,smal lengines, turb ine powered aircraft, and some cars.It was original ly developed to overcome the longchargingt imesassociated with high inductance coils used
in inductive ignition systems, making the igni t ion sys temmore sui table for high eng ine speeds(for small engines,racing engines and rotary piston engines). Capacitordischarge ignition uses capacitor discharge current output tofire the spark plugs.
C.D.I.
(Capacitive Discharge Ignition
System)
http://en.wikipedia.org/wiki/File:Capacitor_Discharge_Ignition_1.jpghttp://en.wikipedia.org/wiki/File:Capacitor_Discharge_Ignition_1.jpghttp://en.wikipedia.org/wiki/File:Capacitor_Discharge_Ignition_1.jpg -
8/12/2019 Ignition Fuel Pump and Spark Plug
30/62
Electronic capaci tor disc harge igni t ion (CDI) systems
have been common on large industrial engines because the
techn ology has beenin use sin ce the 1960's. An advantage of the capacitor discharge ignition system is
that the energy storage and the voltage step up'
funct ions are accompl ished by separate circui t
e lementsallowing each oneto be op t imised for i ts job.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
31/62
Capacit ive discharge ign it ionsystems work b y stor ing energy in anexternal capacito r, which is then discharged into the igni t ion coi lpr imary winding when required. This rate of discharge is much higherthan that found in inductive systems, and causes a correspondingincrease in the rate of voltage rise in the secondary coil winding.
This faster voltage r ise in the second ary wind ing creates a sparkthat can al low combust ion in an enginethat has excess oi lor an overr ich fuel air mixtu rein the combustion chamber. The high ini t ia l sparkvoltage avoids leakage across the spark plug insulator andelectrodescaused by fouling, but leaves much less energy avai lable
for a suff ic ient ly long spark durat ion; this may not be sufficient forcomplete combust ion in a leanburn turbocharged engine resultingin misfiring and high exhaust emissions.
Igni t ion in lean fuel mixtures by capacitor disch arge systems cansometimes only be accompl ished by the use of mult i -spark ignit ion,
where the ignition system duplicates the prolonged spark of inductivespark systems by sparking a number of times during the cycle. This addsgreater stress onto the high-tension leads and can cause considerablespark plug wear and possible failure.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
32/62
Basic principle Most ign i t ion sy stemsused in cars are induct ive igni t ion systems,
which are solely relying on the electric inductance at the coil to produce
high-voltage electricity to the spark plugs as the magnetic field breaksdown when the current to the primary coil winding is disconnected(disruptive discharge). In a CDI system, a charg ing circu i tcharges ahigh voltage capacitor, and dur ing the igni t ion point the systemstop s charging the capacitor, allowing the capacitor to discharge itsoutput to the ignition coil before reaching the spark plug.
A typical CDI modu le consis ts of a smal l transformer, a chargingc i rcu i t, a t r igger ing circui t and a main capacitor. First, the systemvoltage is raised up to 400-600 Vby a transformer inside the CDImodule. Then, the electr ic current f low s to the charging circ ui tandcharges the capacitor. The rect if ier insid e the charging c ircui tprevents capacitor discharge before the ignit ion po int. When thet r igger ing c ircui t receives tr igger ing sign als, the t r igger ing circui tstop s the operat ion of the charging circu i t, allowing the capacitorto discharge its ou tput rapidly to the low inductance ignition coil,which inc rease the 400-600 Vcapacitor discharge to up to 40 kV atthe secondary w indingat the spark plug. When there's no triggeringsignal, the charging circuit is re-connected to charge back the capacitor.
M t CDI d l ll f t t
-
8/12/2019 Ignition Fuel Pump and Spark Plug
33/62
AC-CDI - The AC-CDImodule obtains its electr ic i ty sourcesolelyfrom the alternat ing currentproduced by th e alternator. The AC-CDI
system is the most basic CDI system which is widely used in smal lengines.
Note that not all small engine ignit ion systems are CDI. Some olderengines use magneto ignition. The entire ignition system, coil and points,are under the magnetized flywheel.
If the engine was rotated while examining the wave-form output of thecoil with an oscilloscope, it would appear to be AC. But you mustconsider that since the charge-time of the coil corresponds to much lessthan a full revolution of the crank, the coil really 'sees' only DC current forcharging the external ignition coil.
There exist some electronic ignition systems that are not CDI. Somesystems use a transistor to switch the charging current to the coil off andon at the appropriate times. This eliminated the problem of burned andworn points, and provided a hotter spark because of the faster voltagerise and collapse time in the ignition coil.
Most CDI modules are generally of two types:
-
8/12/2019 Ignition Fuel Pump and Spark Plug
34/62
DC-CDI - The DC-CDI module is powered by the battery, andtherefore an additional DC/AC inverter circuit is included in the CDImodule to raise the 12 V DC to 400-600 V DC, making the CDI
module slightly larger. However, vehicles that use DC-CDI systems
have more precise ignition timing and the engine can be started
more easily when cold.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
35/62
Advantages and Disadvantages of CDI
A CDI sy stemhas a shor t charg ing t ime, a fast vol tager ise (between 3 ~ 10 kV/s) compared to typicalinduct ive sys tems (300 ~ 500 V/s) and a shor t sparkdurat ion limited to about 50-80 s. The fast vol tage risemakes CDI sys tems insensi t ive to shunt resistance, butthe l imi ted spark du rat ion can for some applications betoo short to p rovide rel iable igni t ion. The insensitivity toshunt resistance and the ability to fire multiple sparks canprovide improved cold starting ability.
VACUUM ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
36/62
VACUUM ADVANCE
The vacuum adavnce on spark timing is necessary because the lean mixtures require an
earlier spark timing than the rich mixtures. Therefore as the throttle is closed the spark
must be advanced for optimum performance
-
8/12/2019 Ignition Fuel Pump and Spark Plug
37/62
Vacuum advance
When an engine is at idle, it experiences high manifold
vacuum. If you have ever popped a vacuum line off of an
idling automobile engine, then you have heard the loud
hissthat results. That is manifold vacuum suction. Because
the fuel is traveling so slowly and the engine is under
no load, the vacuumin the engine operatesthe advanceon the distr ibuto r, which then advances the timing so the
engine idles smoothly and the spark is happening at the
correct time. When the accelerator is depressed hard or
when the vehicle is under a good load, there is essentiallyzero manifold vacuum. Therefore, the advance mechanism
on the distributor is not actuated at all, resulting in no timing
advance.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
38/62
VACUUM ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
39/62
Vacuum advance mechanism
Vehic les equipped with vacuum advanced distributors (usually older
models) have a "pod" on the side of the distributor, with a rubber hose
attached to it. The hose connects directly to the intake manifold of the
engine so that it receives the full vacuum, or lack there of.
At id le,
when themanifo ld vacuum is high
, the tube attached to theadvance pod wil l suck in, causing the distr ibu tor to advance the
t iming. There are spr ings ins ide the dis t r ibutor which hold the
t iming mechanism in place. They remain in that posit ion until the
manifold vacuum affects them.
Newer automobi les sometimes use a centr i fugal sys tem that uses
weights ins tead of vacuum. The problem with them is that they are
based only on engine RPM(revolutions per minute) and cannot d etect
whether or no t the engine is under a load or no t. Because of that, the
vacuum advanced systems are much more efficient at advancing or
retarding the timing to the engine's needs.
CENTRIFUGAL SPARK ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
40/62
CENTRIFUGAL SPARK ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
41/62
centrifugal advance mechanism
The centr i fugal advance mechanism advances the ignition
spark as engine speed increases. This is accom pl ished by
twoweights attached to the cam. As the engine's sp eedand
that of the distr ibuto r shaft increase, the weights move
outw ard by centr i fugal force, thereby turning the cam andcausing th e igni t ion to advance.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
42/62
CENTRIFUGAL ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
43/62
CENTRIFUGAL ADVANCE CONTD..
As speed increases, centrifugal force on the weights movesthem outwards against spring tension.
This movement causes the distributor cam or trigger wheelto move ahead. With this design, the higher the engine speed,the faster the distributor shaft turns, thefarther out the advance weights move, and the farther
ahead the cam or trigger wheel is moved forward or advanced.At a preset engine speed, the lever strikes a stop andcentrifugal advance reaches maximum.
The action of the centrifugal advance causes the contact points
to open sooner, or the trigger wheel and pickup coil turn offthe ECU sooner. This causes the ignition coil to fire with theengine pistons not as far up in the cylinders.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
44/62
COMPUTERIZED
ADVANCE
COMPUTERIZED ADVANCE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
45/62
COMPUTERIZED ADVANCE The computer ized advance, also known as an electronic spark
advance system, uses various engine sensors and a computer tocontrol ignition timing. The engine senso rs check variousoperat ingcondi t ionsand sends electr ical data to the com puter
The computer an change ignition timing for maximum engine efficiency.Ignition system engine sensors include the following:-
1. ENGINE SPEED SENSOR (reports engine speed to the computer)2. CRANKSHAFT POSITION SENSOR (reports piston position)
3. THROTTLE POSITION SWITCH (notes the position of the throttle)
4. INLET AIR TEMPERATURE SENSOR(checks the temperature ofthe air entering the engine)
5. ENGINE COOLANT TEMPERATURE SENSOR (measures theoperating temperature of the engine)
6. DETONATION SENSOR (allows the computer to retard timing whenthe engine knocks or pings)
7. INTAKE VACUUM SENSOR (measures engine vacuum, an indicator ofload) The computer receives different current or voltage levels (inputsignals) from these sensors.
It i d t dj i i i ti i b d i d i i
-
8/12/2019 Ignition Fuel Pump and Spark Plug
46/62
It is programmed to adjust igni t iontiming based on engine condi t ions.The com pu ter may be moun ted on the air cleaner, under the dash, ona fender panel, or under a seat. The following is an example of theoperation of a computerized advance. A vehic le is travel ing down theroad at 50 mph ; the speed sensor detects moderate engine
speed.
The thrott le posit ion sensor detectspart thro tt le and the air inlet andcoo lant temperature sensors report normal operat ing temperatures.The in take vacuum sensor sends high vacuum signals to thecomputer. The com puter receivesall the dataand calculatesthat the
engine requires maximum spark advance. The t iming would occurseveral degrees befo re TDCon the compress ion stroke. This act ionassuresthat high fuel economyis attained on the road.
Ifthe operator began to p ass another vehic le, in take vacuum sensordetects a vacuum drop to near zero and a signal is sent to the
computer. The thrott le posit ion sensor detects a wide, open throt t leand other sensor outputs say the same.
The com puter receives and calculates the data, then, if required,retards ign it ion t iming to prevent spark knoc k.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
47/62
Mechanical
Fuel Pump
Mechanical Fuel Pump
-
8/12/2019 Ignition Fuel Pump and Spark Plug
48/62
Mechanical Fuel Pump A mechanical fuel pumpis a device that del ivers fuel to the engine.
Due to the fact that mechanical fuel pumps generally work best on
carbu reted engines, they are typically found only on older vehicles. Acarburetor squats over the engine on many older cars and delivers fuel
into the combustion chambers via intake ports. Some older cars ran
the fuel lines below the gas tank so that gravity does the work of
carrying gasoline from the tank to the carburetor. However, many older
models needed a little additional help to get the fuel from the tank tothe carburetor. The mechanical fuel pump, which was usually located
on the side of the engine, was therefore designed to run off of the
enginesmomentum and provide the carburetor with a steady supply of
fuel.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
49/62
FIGUREA mechanical fuel pump.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
50/62
-
8/12/2019 Ignition Fuel Pump and Spark Plug
51/62
A mechanical fuel pumpmounts to the side of the engine. A leverorpush ro d on the pump passes through an opening in the side oftheengine and l ines up w ith a special lobe on th e camshaft. As thecamshaft turns, the lobe moves the lever up and down, raising and
lowering a flexible diaphragm inside the pump. With the mot ion of thediaphragm, gasol ine is drawn down the fuel l ines and into thepump. From there, the gasoline is pushed into the carburetor, whichuses the vacuum of the engine to pull fuel into the combustionchambers.
Because diaphragm fuel pumps run d irect ly
off of the engine, they will only work when
the engin e is runn ingor being started. This
prevents dangerous bui ldups of fuel f rom
occurr ing in the l ines. Mechanical fuel pumps
also do not pressur ize the system veryhighly:-
Most carbureted fuel systems run as low as 4
pounds per square inch (psi), and rarely ever
more than 15 psi.
S f f
http://en.wikipedia.org/wiki/File:Fuelpump1.jpg -
8/12/2019 Ignition Fuel Pump and Spark Plug
52/62
Since diaphragm fuel pumps are located r ight on the side of theengine, replacing this part is relatively easy and qu ick. However,despite the low pressure levels of carbureted fu elsystems, if youdisco nnect the l ine that feeds into a mechanical fuel pump, i t wi l ldr ip fuel. The fuel l ine is below th e gas tank, sogravi ty willcont inuously pul l fue l down the l ine if you do not plug it. You willalso need to be sure that you correctly line the lever or push rod upwith the enginescamshaft when installing the new fuel pump, so thatyou do not inadvertently damage the pump when you turn the engineover.
Eventually electronic fuel injection systems, which were favored forgreater accuracy and cont ro l, replaced carburetors. When thishappened, cars also began to require fuel systems that ran underhigh pressure, generally between 40 and 60 psi. Because amechanical fuel pump cannot su ppor t a system under that muchpressure, they were eventually cast aside in favor of the higher
performing electronic fuel pump.
Decline of mechanical pumps
-
8/12/2019 Ignition Fuel Pump and Spark Plug
53/62
Decline of mechanical pumps As engines moved away from carburetors and towards fuel
in ject ion, mechanical fuel pumpswere replaced with electr ic fuelpumps, because fuel injection systems operate more eff ic iently at
higher fuel pressures (40-60psi) than mechanical pumps cangenerate. Electr ic fu el pumps are general ly located in the fuel tank,in order to use the fuel in the tank to cool the pum p and to ensu reasteady supp ly of fuel.
Another benefit of an in-tank moun ted fuel pump is that a suc t ion
pumpat the engine could su ck in air througha (difficult to diagnose)faul ty hose connect ion, while a leaking connect ion in a pressurel ine wil l show itsel f immediately. A potential hazard of a tank-mounted fuel pump is that all of the fuel lines are under high pressure,from the tank to the engine. Any leak w il l be easily detected, but isalso hazardous .
Electr ic fuel pum pswill run w henever they are sw itched on, whichcan lead to extremely dangerous situat ions if there is a leak du e tomechanical faultor an accident. Mechanical fuel pum ps are muchsafer, due to their lower operat ing p ressuresand because they 'turnoff' when the engine stops running.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
54/62
WARNING:A leaky fuel pum p is dangerous because thefuel may ignite and s tart a f ire!
Another way to check the pump is to disconnect the fuelline at the carburetor and place the end of the line into acontainer. Crank the engine to see if the pump is pushingany fuel through the line. Strong steady spurts of fuelmean the pump is working. No fuel or a weak streammeans a bad pump, a plugged fuel filter, fuel line
blockage or no fuel in the tank.
WARNING:Do not smoke near gasol ine, and do not al lowany sparks near the carbu retor o r open fuel l ine as this
may igni te the fuel causing a f i re! Do no t spi l l gasol ine ona hot engine. Wait un t i l the eng ine has co oled to work onthe fuel system . A lso, avoid sk in contact with gasol ineand do not b reathe the vapo rs.
-
8/12/2019 Ignition Fuel Pump and Spark Plug
55/62
Electronic
Fuel Pump
-
8/12/2019 Ignition Fuel Pump and Spark Plug
56/62
The fuel pump is a subm ers ib le pumpwith a permanent magnet electr icmoto r. Fuel enters the pump inlet tube
after passing through a sock style filter
and is pushed through the pump by the
motor to the outlet.
Electronic Fuel Pump
It cons is ts of a motor, a vane rol ler pump, a fuel damper,
and a rel ief valve to prevent system damage from overpressure. The fuel pump shares its mounting cage with the fuel
gauge sending unit.
http://www.bombayharbor.com/productImage/0541578001259997016/Electric_Fuel_Pump.JPG -
8/12/2019 Ignition Fuel Pump and Spark Plug
57/62
Long t ime back when the diesel
-
8/12/2019 Ignition Fuel Pump and Spark Plug
58/62
Long t ime backwhen the dieselengines had not much evolvedlike today, to extract bestper formance and long l i fe
adequate fuel pressure in thel ines was necessary for dieselpump& nozzlesto workat theiropt imum. Over a per iod oft ime, the pump used to getweak leading to drop in fuelpressure in lines and laboriousworking of the engine. Thisused to resul t in fue l pumpcal ibrat ion that was a cost lyaffair.
FIGURE A typical fuel pump model assembly, which
includes the pickup strainer and fuel pump, as well as the
fuel-pressure sensor and fuel level sensing unit.
T t i f
-
8/12/2019 Ignition Fuel Pump and Spark Plug
59/62
To ensure opt imum per formance,additional electr ic fuelpump, either inthe tank or near diesel fi l ter intakeused to be instal led; not in all but in
some where the owners wereknowledgeable or the mechanicsuggested so. In addition to maintainingproper fuel pressure, one problem thatwas the bane of all diesel owners wasof air interlock that was due to, no fuel,
damaged fuel line, frayed 'o' ring of thefilters etc., that resulted in stalling,misfiring etc. Electric fuel pumpremoved the air interlock problem.
FIGURE A roller cell-type electric fuel pump.
SPARK PLUG CONSTRUCTION
-
8/12/2019 Ignition Fuel Pump and Spark Plug
60/62
-
8/12/2019 Ignition Fuel Pump and Spark Plug
61/62
SPARK PLUG HEAT RANGE
-
8/12/2019 Ignition Fuel Pump and Spark Plug
62/62
SPARK PLUG OPERATING TEMPERATURE