TM 5-3895-346-14
ENGINE OVERHAUL
TROUBLESHOOTING (ENGINE)
B. Compression pressure may be leaking past the cylinder-head gasket, the valve seats, the injector tube or a
hole in the piston.
Engine Out of Fuel
The problem in restarting an engine after it has run out of fuel stems from the fact that after the fuel is ex-
hausted from the fuel tank, fuel is then pumped from the primary fuel strainer and sometimes partially re-
moved from the secondary fuel filter before the fuel supply becomes insufficient to sustain engine firing.
Consequently, these components must be refilled with fuel and the fuel pipes rid of air in order for the system to
provide adequate fuel for the injectors.
When an engine has run out of fuel, there is a definite procedure to follow for restarting it:
1. Fill the fuel tank with the recommended grade of fuel oil. If only partial filling of the tank is possible, add a
minimum of ten gallons (38 litres) of fuel.
2. Remove the fuel strainer shell and element from the strainer cover and fill the shell with fuel oil. Install the
shell and element.
3. Remove and fill the fuel filter shell and element with fuel oil as in Step 2.
4. Start the engine. Check the filter and strainer for leaks.
NOTE
In some instances, it may be necessary to remove a valve rocker cover and loosen a fuel pipe nut to
bleed trapped air from the fuel system. Be sure the fuel pipe is retightened securely before replacing the
rocker cover.
Primer J 5956 may be used to prime the entire fuel system. Remove the filler plug in the fuel filter cover and
install the primer. Prime the system. Remove the primer and install the filler plug.
Fuel Flow Test
The proper flow of fuel is required for satisfactory engine operation. Check the condition of the fuel pump, fuel
strainer and fuel filter as outlined in Troubleshooting.
Crankcase Pressure
The crankcase pressure indicates the amount of air passing between the oil control rings and the cylinder liners
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.
Check the crankcase pressure with a manometer connected to the oil level dipstick opening in the cylinder
block. Check the readings obtained at various engine speeds with the Engine Operating Conditions
Specifications.
NOTE
The dipstick adaptor must not be below the level of the oil when checking the crankcase pressure.
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