Engine Maintenance (Rev. 12/03)
51
POSITIVE CRANKCASE VENTILATION
The Positive Crankcase Ventilation (PCV) system ducts
gases formed in the crankcase directly to the intake. Harm-
ful vapors that would otherwise collect in the crankcase and
contaminate the oil, or escape to the outside, are now drawn
back into the engine and burned.
The PCV valve is located in the valve cover. It uses a spring
and diaphragm to maintain a constant flow of crankcase gas
regardless of the intake manifold pressure. The crankcase
pressure is consistently regulated, even in the presence of
ring wear and air cleaner clogging.
The following schematics illustrate the Positive Crankcase
Ventilation (PCV) operation. In the unrestricted position,
Figure 1, gas flow exits the crankcase via the push rod pas-
sages and past the orifice and diaphragm. In the past, as air
cleaner restriction increased, vacuum and flow would
increase in the crossover line—lowering the crankcase pres-
sure. To prevent this, the PCV diaphragm, Figures 2 & 3,
expands into the passageway—restricting the flow to main-
tain a constant, slightly positive crankcase pressure.
Figure 1:
Figure 2: Partially
Figure 3: Fully
Unrestricted Position
Restricted Position
Restricted Position
1.
Diaphragm
5.
Push Rod Passages
2.
PVC Valve
6.
Baffle Plate
3.
Spring
7.
To Crossover Tube
4.
Valve Cover
Positive Crankcase Ventilation System Operation
AGA152
Checking Crankcase Pressure
(See Figure 2-63, Measuring Crankcase Pressure, from
Overhaul Manual - di 2.2 and se 2.2, TK 8009-3; pg. 33.)
Use a 127 to 254 mm (5 to 10 in.) Magnehelic Gauge to
measure crankcase pressure. At High and Low Speed the
crankcase pressure should be between 51 to 76 mm (2 to
3 in.) H
2
O.
If crankcase pressure is more than 76 mm (3 in.) H
2
O:
•
Restriction in hose (dirt or ice). -or-
•
PCV diaphragm is frozen to seat in valve. -or-
•
Plugged atmospheric vent hole in PCV cover.
If crankcase pressure is below 0 mm (0 in.) H
2
O (in
vacuum):
•
PCV diaphragm has torn and is no longer controlling
gas flow.
Содержание SB-190 30
Страница 4: ......
Страница 8: ......
Страница 14: ...4...
Страница 26: ...Unit Description Rev 12 03 16 Front View AJA890...
Страница 27: ...Unit Description Rev 12 03 17 1 Defrost Damper 2 X430L Compressor 3 se 2 2 Engine Back View 1 2 3 AJA894...
Страница 30: ...Unit Description Rev 12 03 20 ARA158 1 DAS Optional 2 Relay Board 3 Microprocessor Control Box Components 1 2 3...
Страница 40: ...Operating Instructions Rev 12 03 30...
Страница 74: ...64...
Страница 92: ...82...
Страница 100: ...90...
Страница 113: ...103 SB 100 190 Schematic Diagram Page 1 of 2...
Страница 114: ...104 SB 100 190 Schematic Diagram Page 2 of 2...
Страница 115: ...105 SB 100 190 Wiring Diagram Page 1 of 5...
Страница 116: ...106 SB 100 190 Wiring Diagram Page 2 of 5...
Страница 117: ...107 SB 100 190 Wiring Diagram Page 3 of 5...
Страница 118: ...108 SB 100 190 Wiring Diagram Page 4 of 5...
Страница 119: ...109 SB 100 190 Wiring Diagram Page 5 of 5...