DETROIT DIESEL
Trouble Shooting
cylinder head gasket, valve seats, injector tubes or
2. Stop the engine and remove the fuel pipes from the
No. 1 injector and the fuel connectors.
through a hole in the piston.
3. Remove the injector and install adaptor J 7915-02
and pressure gage and hose assembly J 6992 (Fig. I).
Engine Out of Fuel
4. Use a spare fuel pipe and fabricate a jumper
The problem in restarting the engine after it has run
connection between the fuel inlet and return fuel
out of fuel stems from the fact that after the fuel is
connectors to permit fuel to flow directly to the fuel
exhausted from the fuel tank, fuel is then pumped
return manifold.
from the primary fuel strainer and sometimes partially
removed from the secondary fuel filter before the fuel
supply becomes insufficient to sustain engine firing.
5. Start the engine and run it at 600 rpm. Observe and
Consequently, these components must be refilled with
record the compression pressure indicated on the gage.
fuel and the fuel pipes rid of air in order for the
system to provide adequate fuel for the injectors.
NOTE: Do not crank the engine with the
starting motor to check the compression
When an engine has run out of fuel, there is a definite
pressure.
procedure to follow for restarting it. The procedure is
outlined below:
6. Perform Steps 2 through 5 on each cylinder. The
compression pressure in any one cylinder should not
1. Fill the fuel tank with the recommended grade of
be less than 430 psi (540 psi for "N" engines) at 600
fuel oil. If only partial filling of the tank is possible,
r p m . In addition, the variation in compression
add a minimum of ten gallons of fuel.
pressures between cylinders of the engine must not
exceed 25 psi at 600 rpm.
2. Remove the fuel strainer shell and element from the
strainer cover and fill the shell with fuel oil. Install the
EXAMPLE: If the compression pressure readings
shell and element.
were as shown in Table 2, it would be evident
that No. 3 cylinder should be examined and the
3. Remove and fill the fuel filter shell and element
cause of the low compression pressure be
with fuel oil as in Step 2.
determined and corrected.
4. Start the engine. Check the filter and strainer for
Note that all of the cylinder pressures are above the
leaks.
low limit for satisfactory engine operation. Neverthe-
less, the No. 3 cylinder compression pressure indicates
NOTE: In some instances, it may be necessary to
that something unusual has occurred and that a
remove a valve rocker cover and loosen a fuel
localized pressure leak has developed.
pipe nut in order to bleed trapped air from the
fuel system. Be sure the fuel pipe is retightened
Low compression pressure may result from any one of
securely before replacing the rocker cover.
several causes:
Primer J 5956 may be used to prime the engine fuel
A. Piston rings may b e stuck or broken. To
system. Remove the filler plug in the fuel filter cover
determine the condition of the rings, remove the
and install the primer. Prime the system. Remove the
air box cover and press on the compression rings
primer and install the filler plug.
with a blunt tool. A broken or stuck compression
ring will not have a "spring-like" action.
Fuel Flow lest
B. Compression pressure may be leaking past the
Gage Reading
1. Disconnect the fuel return hose from the fitting at
Cylinder
the fuel tank and hold the open end in a suitable
1
525
psi (3617 kPa)
container.
520
psi (3583 kPa)
2
485
psi (3342 kPa)
3
2. Start and run the engine at 1200 rpm and measure
4
515
psi (3548 kPA
the fuel flow for a period of one minute. At least .6
gallon of fuel should flow from the fuel return hose
`The above pressures ore for an engine operating at
per minute.
an altitude near sea level.
3. Immerse the end of the fuel return hose in the fuel
TABLE 2
in the container. Air bubbles rising to the surface of the
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