Equus 3660 - Hand Vacuum Pump & Brake Bleeding Kit - Manual (Page 11)

3660 9
B. TEST PROCEDURES
As a result of normal engine operation, the PCV valve may become
clogged and reduce the amount of crankcase ventilation. Reduced
ventilation can cause the formation of acids in the crankcase, and a
buildup of pressure which could force engine oil out past the engine
seals. To prevent these problems, the PCV valve should be replaced
periodically.
NOTE: A slow or rough idle can be caused by a clogged PCV valve.
Check the PCV system BEFORE adjusting engine idle.
AIR CLEANER
CARB.
INT. MAN.
ROCKER COVER
CRANK CASE
1
2
3
FRESH AIR
(CLOSURE)
TUBE
OIL FILLER
CAP
FRESH AIR
FLOW
AIR AND
CRANKCASE
VAPOR FLOW
PCV VALVE
CONTROLS
FLOW RATE
OIL SEPARATOR
HIGH VACUUM
PULLS VALVE
TOWARD TOP SEAT VACUUM
IS LOW BACKFIRE CAUSES
HIGH PRESSURE
IN MANIFOLD
CRANKCASE PRESSURE
TENDS TO CLOSE VALVE
FLOW
RATE
IS
LOW
SPRING
OPENS
VALVE
FARTHER
FLOW RATE
INCREASES
PLUNGER
SEATS TO
SEAL OFF
FROM
CRANKCASE
PCV VALVE OPERATING CONDITIONS
NORMAL HIGH SPEED OR LOAD BACKFIRE DURING CRANKING
TYPICAL PCV SYSTEM / PCV VALVE OPERATION
Figure 4. Typical PCV System / PCV Valve Operation