15.2 Trouble Shooting (Engine)
DETROIT DIESEL 53
and record the compression pressure indicated on the gage. Do not crank the engine with the starting motor to obtain the
compression pressure.
6. Perform Steps 2 through 5 on each cylinder. The compression pressure in any one cylinder at a given altitude
above sea level should not be less than the minimum shown in Table 1. In addition, the variation in compression
pressures between cylinders must not exceed 25 psi at 600 rpm.
Low compression pressure may result from any one of several causes:
A. Piston rings may be stuck or broken. To determine the condition of the rings, remove the air box cover and inspect
them by pressing on the rings with a blunt tool. A broken or stuck ring will not have a "spring-like" action.
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 exhausted from
the fuel tank, fuel is then pumped from the primary fuel strainer and sometimes partially removed 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 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 Section 2.0 under Trouble Shooting.
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
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