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3.
APPLICATIONS
The use of a vacuum/pressure gauge is often overlooked when determining
mechanical condition and carrying out fault diagnosis on internal
combustion engines. Monitoring actual manifold vacuum is invaluable
when troubleshooting engine faults. This can only be carried out by using
a good quality vacuum gauge and this, coupled with a hand-operated
vacuum pump, also allows static testing of all types of vacuum operated
systems.
Set out on the following pages are applications that the VACUUM/PRESSURE
PUMP & BRAKE BLEEDING KIT can be used for, but it must always be
remembered that these are examples only and reference to manufacturer’s
service manuals should always be made for correct testing procedures and
specifications.
In addition to this, it is always recommended that additional tests, ie.
compression tests, cylinder leakage tests, ignition timing checks etc. be
carried out to confirm indications of vacuum/pressure gauge readings.
4.
OPERATING INSTRUCTIONS
4.1.
This hand pump and its adaptors can be used to test vacuum
motors and control valves as well vacuum or pressure operated
systems and components that require to be properly sealed. The
pump and its associated accessories can also be used to bleed
brakes. In pressure testing mode the pump may be utilised to
dispense or transfer liquids and provide slight pressure during
gravity or pressure bleeding.
The CT3258 can be used for both pressure and vacuum testing by means of
the sliding sleeve selector at the front end of the pump.
To select PRESSURE testing mode, move the sliding sleeve away from the
nozzle end of the pump until it makes contact with the main body. The hole
indicated at ‚X’ must be fully covered.
To select VACUU M testing mode, move the sliding sleeve away from the
main body of the pump until it makes contact with the ‚O’ ring just behind
the nozzle. The hole indicated at ‚X’ must be fully revealed.
4.2. Analysing Engine Mechanical Condition via Manifold Vacuum
Readings
The gauge readings (See the following figs) are only examples of what may
be observed. It is important to remember that it is the action of the needle
rather than the actual reading that is more important. Varying engine types
will run different manifold vacuum pressures, depending on camshaft
profile, valve overlap, timing etc, so an exact vacuum reading cannot be
specified. The main criteria is that the needle reading is between 16 to
21inHg and steady. Manifold vacuum is also affected by altitude and it will
drop approximately 1inHg for every 1000 feet above sea level so this must
also be considered whenassessing manifold vacuum actual readings.
Step1.
Run engine until normal operating temperature is reached. Switch
engine off.
Step 2.
Locate and connect the vacuum gauge to a port directly on the
manifold (fig.2) or on the carburettor/throttle body below the throttle
butterfly.
Step 3
. Start and run the engine at idle, observing the gauge reading.
Refer to the gauge examples on the right of this page to indicate any
problems and their possible causes.
(1) READING:
16 -
21inHG
DIAGNOSIS:
NORMAL
(2) READING:
When the throttle is
suddenly opened then
released, the needle
should drop to below
5 inHg then bounce
up to approximately
25 inHg before
settling back to the
original reading.
DIAGNOSIS:
NORMAL
(3) READING:
Extremely low but
steady
DIAGNOSIS:
leaking
intake manifold
system, Faulty
manifold gasket or
carburettor base
gasket, split vacuum
hose, seized open EGR
valve.
(4) READING:
reading
low but steady
DIAGNOSIS:
Retarded
ignition timing.
Confirm using timing
light and reset to
manufacturer’s
specification.
(5) READING:
Reading
slightly low and
fluctuating slowly.
DIAGNOSIS:
Over
lean or rich mixture.
Check and reset in
accordance with
manufacturer’s
(6) READING:
Regular
fluctuation between
normal and low.
DIAGNOSIS: Blown
head gasket
between two
adjacent cylinders.
Carry out cylinder
leakage test.
(7) READING:
Reading
slightly lower than
normal including
when throttle is
suddenly opened then
released.
DIAGNOSIS:
Worn
piston rings. Carry out
compression test.
(8) READING:
Regular
drop
Between normal and
low reading.
DIAGNOSIS:
Burnt
valve.
(9) READING:
Normal
when First started but
drops rapidly when
RPM held at 3000.
DIAGNOSIS:
Restriction in exhaust
system.
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