Urrea 2012 Manual De Usuario Y Garantía página 9

READING:
lower than for normal engine
including
suddenly opened then released.
CAUSE: Worn piston rings, carry
out compression test.
READING:
between
reading.
CAUSE: Burned valve.
READING: Normal when first
started but drops rapidly with
RPM held at 3,000.
CAUSE: Restriction in exhaust
system.
IGNITION SYSTEM
VACUUM ADVANCE
On standard points and some electronic ignition
systems there are two types of advance methods
used, both of which must function correctly
to obtain maximum performance and fuel
economy.
The first method is mechanical or centrifugal,
which operates by the use of weights located
in the base of the distributor. The weights
throw outwards advancing ignition timing as
engine RPM increases. This is tested by firstly
removinng the vacuum advance line to disable
the system, then with a turning light connected
run the engine RPM up checking that the timing
advances in accordance with the manufactures
specification.
The second method is vacuum advance, wich
senses engine load via manifold vacuum. A
vacuum diaphragm is mounted onto the
distributor and connected to a rotating internal
base plate which advances or retards timing as
required to suit varying engine loads.
Reading slighly
when throtle is
Regular drop
normal and low
To test this system for correct operation again
with the timing light connected raise the
engine RPM and check timing advance against
manufacturers specifications. In the event that
the vacuum advance is not operating, remove
the vacuum line from the distributor advance
is not operating, remove the vacuum line from
the distributor advance mechanism. Connect the
test vac pump and create a 5-10 inch vacuum,
monitoring the timing at the same time.
If a timing advance is noted this confims that the
vacuum diaphragm and mechanical links are in
order and the fault is a vacuum supply.
To confirm this connect the test vac to the
vacuum supply line and check the gauge reading.
No vacuum should be noted at idle but when
the engine RPM is increased a vacuum increase
should also be noted. If this does not occur, trace
the vacuum line back checking for restrictions
and breaks.
FUEL SYSTEMS
Testing mechanical fuel pumps
The testvac can be used to evaluate the condition
of mechanical fuel pumps by testing the vacuum
that is able to create.
Locate and remove the suction line from the
pump. Connect the testvac to the suction port
of the pump, start and run the engine at idle.
The vacuum reading that should be noted will
vary slightly on different makes and models
but as a general rule approximately 15 inHg
should be created. This should also be held
for approximately 1 minute after engine shut
down. If this vacuum reading is not achieved
or the vacuum drops off inmediately with the
engine shut down, the fuel pump requires either
overhaul or replacement.
Carburecttors
There are many different types of vacuum
control systems used on carburettors. Using the
test vac, allows quick and accurate testing of
these systems.
Listed below are just two examples of test
that can be carried out:
Example 1: Testing
diaphragm
With the engine
E N G L I S H
a choke break
at normal operating
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