6.3.3.
Simply remove and block off the vacuum supply line to the pressure regulator, connect and operate the VS4021 vacuum pump (fig.5)
to simulate vacuum pressures in accordance with the manufacturer’s specifications and note variation in fuel pressure reading.
6.4.
TESTING EMISSION CONTROL EXHAUST GAS RECLRCULATION VALVES (EGR)
6.4.1.
Start engine and run at idle until normal operating temperature is reached. Remove the vacuum line from the EGR valve and attach
the VS4021 vacuum tester kit (fig.6). Operate the hand pump to apply approximately 15 inHg of vacuum. If the EGR Valve is working
correctly the engine idle will become rough. If the idle remains unchanged the valve is possibly seized in the closed position. If the
vacuum is not held, the diaphragm in the valve has failed.
7. ADDITIONAL VACUUM SYSTEMS
7.1.
TESTING ONE-WAY VALVES
7.1.1.
Many vacuum operated circuits use in-line one-way valves to apply vacuum in one direction only.
7.1.2.
To test the function of the valve remove it from the circuit. Attach the VS4021 vacuum tester (fig.7) and operate pump to apply vacuum.
In one direction the valve should hold vacuum and in the opposite direction it should not.
7.2.
TESTING ELECTRICALLY OPERATED VACUUM SOLENOIDS
7.2.1.
Electrically operated vacuum solenoids are commonly used in control circuits for air conditioning/ventilation systems, emission control
systems, idle step up systems etc. and testing the function of these when using the VS4021 is extremely simple.
7.2.2.
Locate the solenoid to be tested and remove the line that goes to the component being tested. Connect the VS4021 to the solenoid
port (fig.8) and start the engine. With the system turned off there should be a zero gauge reading. Now turn the system to the ‘on’
position and a gauge reading equal to the manifold vacuum should be observed, if no reading exists remove the vacuum supply line
and test for manifold vacuum at this point. If the vacuum does exist this indicates that the solenoid is faulty or it is not receiving a
‘switch on’ voltage (use a multimeter to test this). If no vacuum exists trace the supply line back to the vacuum source checking for
kinks and breaks.
7.3.
TESTING THERMAL VACUUM SWITCHES
7.3.1.
There are many vacuum controlled circuits that must only operate when the engine reaches normal operating temperature. This is
done using thermal switches that remain in an ‘off’ position until a given temperature is reached.
7.3.2.
To test this type of switch, remove the vacuum supply line coming from the manifold to the switch and test for manifold vacuum. If this
vacuum is correct refit the supply line to the thermal switch and remove the opposing line from the switch. Attach the VS4021 vacuum
tester to the port (fig.9) and start the engine. With a cold engine no reading should be noted. When the engine reaches normal
operating temperature a manifold vacuum reading should be noted.
VS4021.V2 | Issue 2 (F,2,3) 26/02/19
Original Language Version
© Jack Sealey Limited
fig.5
fig.6
fig.7
fig.8
fig.9
