Kostanay
State University, Kazakhstan
Diagnosis
and methods of malfunctions repair in power supply system of carburetor engines
Power supply malfunctions are
formation of inadequate mixture quality and, consequently, increased
consumption. The most frequent power supply malfunction is formation of
concentrated and non-concentrated mixture.
Concentrated fuel mixture has a
reduced burn speed and causes overheat of engine, while his work is accompanied
by sharp claps in muffler. Claps are result of incomplete combustion of mixture
in cylinder (not enough oxygen in air). Afterburning it occurs in muffler and
is accompanied by appearance of black smoke from it.
Long work of engine on concentrated
mixture leads to excessive fuel consumption and a large coke deposits on walls
of combustion chamber in spark plug electrodes, reducing engine power and
increase its wear. Formation of concentrated mixture reduces number of inlet
air or increase amount of supplied fuel.
In the studied carburetors with main
dosing system with pneumatic deceleration of fuel, in case of blockage of air
jet occurs formation of concentrated fuel mixture; This problem is eliminated
by blowing air jets of main dosing system with compressed air.
Increasing the amount of supplied
fuel is possible at increased level of fuel in float chamber due to incomplete
fit shut-off valve, clogging of valve seat, use lighter grades of fuel jets
develop holes, leaky valve closure and partial opening choke.
When valve has gap with saddle it
should be grind or replace. If jet holes are used, the jets are replaced.
Weakly fixed valve of economizer
should be grinded or replaced.
Full opening of air damper is controlled by varying the length of
rope drive.
Poor working mixture also has a low
rate of combustion, the engine is overheating, and his work is accompanied by
sharp claps in the carburetor. Noise in carburetor are the result that mixture
burns in cylinder even when intake valve is already opened, and flame
propagates to inlet conduit and mixing chamber of the carburetor.
Continuous operation of engine at
poor fuel leads to overconsumption due to fact that engine power in this case
falls and often it is necessary to use lower gear.
Formation of poor fuel mixture
facilitates to decrease in amount of fuel supplied, or increasing the number of
incoming air. Reducing amount of supplied fuel may result in jamming of air
valve in fuel filler tube, clogging fuel lines, filters, clarifiers,
malfunction of fuel pump, low fuel level in float chamber, clogging nozzles. Increasing amount of incoming air possibly due to air
leaks at the joints of individual parts of carburetor and at the joints with
intake duct of the carburetor and intake manifold with cylinder head. Valve of
plug fuel filler must be inspected and dust must be remove and pieces of ice
that can form in winter. Clogged pipes purged by pump for inflating tires.
Clogged filters- septic tanks need to be disassembled, cleaned of dirt, rinsed
and blow compressed by air. During
cleaning filters with ceramic element, be careful, because it is very fragile.
While
filter are assembled, special attention should be paid to state of gaskets,
torn gasket must be replaced. Malfunction of fuel pump is usually accompanied
by decrease or cessation of fuel supply.
Most often diaphragm pump has
following faults: damage of diaphragm; gapping valves; wear of outer end of
double-arm lever; decrease in elasticity of the spring.
Damaged discs of diaphragm are
replaced. In case of damage in transit must be released nut drives diaphragm,
carefully separate them so that the injury did not coincide, and lubricated
with soap, build and installed in place. Wrongly mounted valve must be
disassembled, cleaned of dirt, also condition of spring must be checked and
replaced. If this is insufficient, the valve must be replaced. At deterioration
of outer end of his double-arm lever it must be added. As a temporary measure
(in a way), gasket between pump and place of its attachment is replaced by a
thinner, thereby bringing lever to eccentric. Clogged carburetor fuel jets must
be purged. Appling wire or other solid objects to clean jets is prohibited, as
it would lead to increase or change the
shape of jets hole. Air leaks in joints of the carburetor and intake manifold
eliminates tightening fasteners or replace gaskets.
One of the frequent power supply
system failure is flow of fuel through fuel leaks in joints, which is very
dangerous because it can cause a fire. To prevent this fault connections should
be periodically tightened.
Major maintenance work. EO. Check
the fuel level in tank and fill the car with fuel. Check by visual inspection
for leaks connection carburetor, fuel pump, fuel lines and fuel tank.
TS-1. Check for leaks by visual
inspection of supply system fixing; Repair if necessary. Check connection of
pedal arm to throttle and lever to level of choke, the action drives and
completeness of opening and closing throttle and choke valves. Pedal actuator
must be moved in both directions smoothly. After using of car on dirty cars
carburetor filter should be cleaned and oil should be changed.
TS-2. Check the tightness of the
fuel tank and pipeline connections of power supply system, check carburetor and
fuel pump mount; Repair if necessary. Check the connection of thrust to
throttle lever and cable to choke lever, drive action, complete opening and
closing of throttle and choke valves. Check fuel pump pressure gauge (without
removing it from engine). Pump pressure should be in the range of 0.03 ... 0.04
MPa. Check the fuel level in carburetor float chamber with engine with low
engine speed to idle. Rinse engine air filter and change oil in it.
Literature:
1.
Maintenance and repair of the car. In two parts. Part 2: A. Kuznetsov -
Moscow Academy 2012 g.- 256.
2.
Processes car repairs: V.M Vinogradov - St. Petersburg, Academia, 2011-432