DETROIT DIESEL 53
2.0 Shop Notes
satisfactory when the entire surface is a solid dark
powder by rinsing the lapping blocks in trichloroethyl-
grey. Bright or exceptionally dark spots indicate
ene and scrubbing with a bristle brush.
defects and additional lapping is required.
When not in use, protect the lapping blocks against
After the surfaces have been refinished, remove the
damage and dust by storing them in a close fitting
wooden container.
INJECTOR TIMING
If it is suspected that a fuel injector is "out of time".
the injector rack-to-gear timing may he checked
without disassembling the injector.
A hole located in the injector body, on the side
opposite the identification tag, may be used to visually
determine whether or not the injector rack and gear
are correctly timed. When the rack is all the way in
(full-fuel position). the flat side of the plunger will be
visible in the hole. indicating that the injector is "in
time". If the flat side of the plunger does not come
into full view (Fig. 2) and appears in the "advanced"
or "retarded" position, the injector should be
disassembled and the rack-to-gear timing corrected
Fig. 2 lnjector Rack-to-Gear Timing
FUEL INJECTOR SPRAY TIPS
Due to a slight variation in the size of the small
Flow gage J 21085 may be used to select a spray tip
orifices in the end of each spray tip, the fuel output of
that will increase or decrease the fuel injector output
an injector may he varied by replacing the spray tip.
for a particular injector after it has been rebuilt and
tested on the comparator.
EFFECT OF PRE-IGNITION ON FUEL INJECTOR
Pre-ignition is due to ignition of fuel or lubricating oil
assemblies should be removed and checked for burned
in the combustion chamber before the normal
spray tips or enlarged spray tip orifices.
injection period. The piston compresses the burning
Before replacing the injectors, check the engine for the
mixture to excessive temperatures and pressures and
cause of pre-ignition to avoid a recurrence of the
may eventually cause burning of the injector spray tip
problem. Check for oil pull-over from the oil bath air
and lead to failure of the injectors in other cylinders.
cleaner, damaged blower housing gasket, defective
W h e n pre-ignition occurs, all of the injector
blower oil seals, high crankcase pressure, plugged air
box drains, ineffective oil control rings or dilution of
the lubricating oil.
BLUING INJECTOR BODIES AND NUTS
The appearance of the injector body and nut of a
3-1/2 Ibs. of sodium nitrite per gallon of water
rebuilt injector can be enhanced with an oxide finish
obtained through a dipping process known as
1 ounce of phosphoric acid per gallon of water
"bluing". Pre-mixed compounds are available com-
mercially for preparing- the necessary solutions.
The procedure usually follows five (5) steps in
Detailed instructions are usually provided with the
sequence:
commercial compounds. An effective bluing solution
can be prepared in the service shop by mixing the
1. An alkaline solution bath (180 -212 F.) to preclean.
following materials:
6 Ibs. of sodium hydroxide per gallon of water
2. A hot or cold water rinse.
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