TM 5-3810-300-24&P-3
15.2 Trouble Shooting (Engine)
fuel and the fuel pipes rid of air in order for the system to
blower oil seals, defective blower, cylinder head or end
provide adequate fuel for the injectors.
plate gaskets, or excessive exhaust back pressure.
Also, the breather tube or crankcase ventilator should be
When an engine has run out of fuel, there is a definite
checked for obstructions.
procedure to follow for restarting it:
Check the crankcase pressure with a manometer
1
Fill the fuel tank with the recommended grade of
connected to the oil level dipstick opening in the cylinder
fuel oil. If only partial filling of the tank is possible, add a
block. Check the readings obtained at various engine
minimum of ten gallons of fuel.
speeds with the Engine Operating Conditions in Section
2
Remove the fuel strainer shell and element from the
strainer cover and fill the shell with fuel oil. Install the
Exhaust Back Pressure
shell and element.
A slight pressure in the exhaust system is normal.
3
Remove and fill the fuel filter shell and element with
However,. excessive exhaust back pressure seriously
fuel oil as in Step 2.
affects engine operation. It may cause an increase in
the air box pressure with a resultant loss of efficiency of
4
Start the engine. Check the filter and strainer for
the blower. This means less air for scavenging which
leaks.
results in poor combustion and higher temperatures.
NOTE: In some instances, it may be
Causes of high exhaust back 'pressure are usually a
necessary to remove the valve rocker
result of an inadequate or improper type of muffler, an
cover and loosen a fuel pipe nut to bleed
exhaust pipe which is too long or too small in diameter,
trapped air from the fuel system. Be
an excessive number of sharp bends in the exhaust
sure the fuel pipe is retightened securely
system, or obstructions such as excessive carbon
before replacing the rocker cover.
formation or foreign matter in the exhaust system.
Primer J 5956 may be used to prime the entire fuel
Check the exhaust back pressure, measured in inches of
system. Remove the filler plug in the fuel filter cover and
mercury, with a manometer. Connect the manometer to
install the primer. Prime the system. Remove the primer
the exhaust manifold (except on turbocharged engines)
and install the filler plug.
by removing the 1/8 " pipe plug which is provided for that
purpose. If no opening is provided, drill an 11/32 " hole
Fuel Flow Test
in the exhaust manifold companion flange and tap the
hole to accommodate a 1/8 " pipe plug. Check the
readings obtained at various speeds (at noload) with the
The proper flow of fuel is required for satisfactory engine
Engine Operating Conditions in Section 13.2.
operation. Check the condition of the fuel pump, fuel
strainer and fuel filter as outlined in Section 2.0 under
Air Box Pressure
Trouble Shooting.
roper air box pressure is required to maintain sufficient
Crankcase Pressure
air for combustion and scavenging of the burned gases.
Low air box pressure is caused by a high air inlet
The crankcase pressure indicates the amount of air
restriction, damaged blower rotors, an air leak from the
passing between the oil control rings and the cylinder
air box (such as leaking end plate gaskets) or a clogged
liners into the crankcase, most of which is clean air from
blower air inlet screen. Lack of power or black or gray
the air box. A slight pressure in the crankcase is
exhaust smoke are indications of low air box pressure.
desirable to prevent the entrance of dust. A loss of
engine lubricating oil through the breather tube,
High air box pressure can be caused by partially plugged
crankcase ventilator or dipstick hole in the cylinder block
cylinder liner ports.
is indicative of excessive crankcase pressure.
Check the air box pressure with a manometer connected
The causes of high crankcase pressure may be traced to
to an air box drain tube.
excessive blow-by due to worn piston rings, a hole or
crack in a piston crown, loose piston pin retainers, worn
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