Owner's manual
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
CP7803
VACUUM GAUGE/
PRESSURE TESTER KIT
INSTRUCTIONS
CRANKING VACUUM TESTS
Engine Condition Test
1. Start engine and allow it to warm to normal
operating temperature. Stop engine. To pre-
vent the engine from starting, disable the igni-
tion system.
2. Remove the air filter. Back out the idle speed
screw (see Figure 1) until the throttle valve is
tighly closed. If the carburetor is also equipped
with an idle air bleed screw, turn the screw
clockwise until it bottoms lightly. In both cases,
count the number of turns so the screws can be
returned to their original positions after the tests.
3. If the vehicle is equipped with an idle stop
solenoid (See Figure 1), disconnect the electri-
cal wire at the base of the solenoid under the
rubber boot or at the connector as shown.
4. If the engine is equipped with a PCV (Positive
Crankcase Ventilation) system, remove the PCV
valve at the engine rocker arm cover (see Fig-
ure 2) and plug the valve on the bottom with
tape or other suitable means.
5. Using the hose supplied, connect the Vacuum
Gauge to a source of manifold vacuum. This
may be a fitting on the carburetor below the
throttle plate, or a fitting in the intake manifold.
See Figures 2 and 9.
6. Crank the engine and note Vacuum Gauge
reading.
(After testing, return adjustment screws to their
original positions.)
Test Results
The general condition of an engine is indicated by
one of three possible gauge readings:
A.(Figure 3) A reasonably steady vacuum read-
ing of 4 inches or more on emission controlled
engines, and 10 inches or more on non-emis-
sion controlled engines (pre-1968) indicates
correct engine vacuum. Readings may vary
considerably on different engines, but should
not fall below these minimums. (See
manufacturer’s specifications).
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
Fig. 3
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
Fig. 4
Test Results
A.(Figure 6) A steady reading between 15 and 22
inches indicates a mechanically sound engine.
B.(Figure 7) A pointer which sweeps or wanders
erratically through several inches indicates a
malfunction affecting all cylinders unequally
and inconsistently. To help isolate the troubled
area, run the engine at about 2000 RPM. If the
pointer steadies, check for:
1. Ignition and/or timing.
2. Carburetor mixture adjustment at idle.
If the sweep gets larger, check for weak or
broken valve springs. If the sweep becomes
shorter and more rapid, check for:
1. Carburetor or intake manifold leaks.
2. Sticky valves.
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
Fig. 5
EXHAUST RESTRICTION TEST
With vacuum gauge connected to a source of
manifold vacuum, increase engine speed to 2000
RPM, maintain this speed, and note the vacuum
gauge reading. A gradually decreasing vacuum
reading may indicate a restricted exhaust system.
(Partially blocked muffler or tailpipe.)
POSITIVE CRANKCASE
VENTILATION (PCV) VALVE TEST
1. Unplug the PCV valve, plugged previously with
a piece of tape (Step 4, Cranking Vacuum
Tests) and crank engine.
A. If the PCV valve is operating properly, the
vacuum will drop to about one-half the value
noted in Step 6, Cranking Vacuum Tests.
B. A reading much lower than one-halfindicates
excessive flow which could upset the proper
carburetor air/fuel ratio causing rough idling
and burned valves.
C. No change in the vacuum indicates a clogged
PCV valve.
2. Return the idle screw (and idle air bleed screw)
to its original position. (See Step 2, Cranking
Vacuum Tests).
3. Re-enable the ignition system.
4. Re-connect the wire to the idle stop solenoid.
5. Re-connect all hoses and vacuum lines.
6. Re-install the PCV valve in its proper location.
PCV SYSTEM TEST
1. Operate the engine at normal temperature and
idle speed.
2. Remove the hose connected between the air
cleaner and valve cover or oil filler/breather cap
as shown in Figure 8. Plug the oil dipstick tube
to prevent an air leak.
Fig. 6
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
0
Engine
Vacuum
5
10
15
20
25
30
10
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
Fuel
Pump
psi
IDLE STOP
SOLENOID
RUBBER
COVER
PCV
VALVE
AIR CLEANER
ROCKER ARM
VALVE COVER
Fig. 2
IDLE MIXTURE
SCREWS
DISCONNECT
ELECTRICAL
CONNECTOR OR
TERMINAL UNDER
RUBBER COVER
IDLE
SPEED
SCREW
SOURCE OF
MANIFOLD
VACUUM
CLOSED
BREATHER
CAP
B.(Figure 4) An excessively low, steady vacuum
is caused by a condition which affects all cylin-
ders equally.
Check for:
1. Leaking carburetor flange gasket.
2. Worn carburetor throttle shaft.
3. Leaking vacuum lines.
4. Improper valve timing.
5. Slow engine cranking due to:
A. Battery
B. Battery cable connections
C. Defective starter motor
D. Excessive mechanical drag in engine caused by:
1. Tight fitting pistons in rebuilt engine.
2. Thickened oil due to excessive oxidation.
C.(Figure 5) A reading which pulses unevenly
indicates a leaky condition which affects one or
more, but not all cylinders.
NOTE: A certain amount
of even pulsing is nor-
mal, notably on 6 and 4
cylinder engines, and
does not necessarily in-
dicate a leaky condition.
Check for:
1. Burned or stuck valve.
2. Intake manifold leak
at one cylinder.
3. Worn intake valve
guide.
4. Broken piston or piston rings.
RUNNING VACUUM TEST
Engine Condition Test
While performing a running vacuum test, it is
possible to obtain a different gauge indication than
that obtained under the cranking vacuum test.
1. Connect the vacuum gauge to a source of
manifold vacuum. See Figures 2 and 9.
2. Run the engine at normal operating tempera-
ture and idle speed.
Fig. 7
®
Fig. 1
PLUG OIL
DIPSTICK HOLE
AIR
CLEANER
FILLER/BREATHER CAP
VENT
HOSE
Fig. 8
UNIVERSAL
RUBBER
ADAPTER