DETROIT DIESEL
Trouble Shooting
EXHAUST BACK PRESSURE
CRANKCASE PRESSURE
(max. In inches of Mercury)
(max. In inches of water)
Engine
No-Load Speed (rpm)
Engine
Speed (rpm)
1800
2000
2200
2500
2800
1800
2000
2200
2500*
2800*
*
*
3-53
.5
.5
.5
.9
1.0
3-53
1.3
1.7
2.1
2.7
2.7
4-53
.5
.5
.5
.9
1.0
4-53
1.3
1.7
2.1
2.7
2.7
4-53T
-
-
-
1.0
-
6V-53
-
-
-
.9
1.0
4-53T
-
-
-
1.8
-
6V-53
-
-
2.7
2.7
*Engines with four valve cylinder head(s).
*Engines with four valve cylinder head(s).
3.8 for Marine engines.
TABLE 4
TABLE 3
fuel will indicate air being drawn into the fuel system on the suction side of the pump.
If air is present, tighten all fuel line connections between the fuel tank and the fuel pump.
If the fuel flow fails to meet the amount specified, the fuel strainer, filter or pump should be serviced.
Crankcase Pressure
The crankcase pressure indicates the amount of air passing between the oil control rings and the cylinder liner into the
crankcase, most of which is clean air from the air box. A slight pressure in the crankcase is desirable to prevent the
entrance of dust. A loss of engine lubricating oil through the breather tube, crankcase ventilator or dipstick hole in the
cylinder block is indicative of excessive crankcase pressure.
The causes of high crankcase pressure may be traced to excessive blow-by due to worn piston rings, a hole or crack in a
piston crown, loose piston pin retainers, worn blower oil seals, defective blower, cylinder head or end plate gaskets, or
excessive exhaust back pressure. Also, the breather tube or crankcase ventilator should be checked for obstructions.
The crankcase pressure may be checked with a manometer connected to the oil level dipstick opening in the cylinder
block. Check the readings obtained at various engine speeds with the specifications in Table 3.
Exhaust Back Pressure
A slight pressure in the exhaust system is normal. However, excessive exhaust back pressure seriously affects engine
operation. It may cause an increase in the air box pressure with a resultant loss in the efficiency of the blower. This
means less air for scavenging, which results in poor combustion and higher temperatures.
Causes of high exhaust back pressure are usually a result of an
AIR BOX PRESSURE
inadequate or improper type of muffler, an exhaust pipe which is
(min. in inches of Mercury)
too long or too small in diameter, an excessive number of sharp
Max. Exhaust Back Pressure (Full Load)
bends in the exhaust system, or obstructions such as excessive
Engine
Speed (rpm)
carbon formation or foreign matter in the exhaust system.
800
2000
2200
2500*
2800*
3-53
5.5
6.9
8.6
8.0
9.3
4-53
5.5
6.9
8.6
8.0
9.3
The exhaust back pressure, measured in inches of mercury,
4-53T
-
-
-
33.5
-
may be checked with a manometer, or pressure gage,
6V-53
-
-
-
8.0
9.3
connected to the exhaust manifold.
(Zero Exhaust Back Pressure)
Remove the 1/8" pipe plug, which is provided for that purpose,
3-53
3.8
4.9
6.2
4.8
6.1
from the manifold. If there is no opening provided, one can be
4-53
3.8
4.9
6.2
4.8
6.1
made by drilling an 11/32" hole
4-53T
-
-
-
31.5
-
6V-53
-
-
4.8
6.1
TABLE 5
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