Mack MP7 - Page 226

REPAIR INSTRUCTIONS, PART 1
Page 215
4. Before reusing an injector, cleaning is
required to ensure suitability for reuse.
Before doing any cleaning, the injector fuel
inlet and outlet ports and the electrical
connector opening must be covered to
prevent contamination from the cleaning
process. Also, there must be no lower O-ring
installed in the injector. Refer to “UNIT
INJECTOR CLEANING” on page 268 for
further information.
5. Remove the bore sealing plug, 9998251.
283
Figure 283 — Unit Injector Bore Sealing Plug
6. Install new O-rings on the unit injector as
follows:
앫 Upper ring — large diameter, violet
앫 Lower ring — small diameter, violet
7. Lubricate both O-rings and the cylinder head
injector bore with clean engine oil.
8. Install a new injection nozzle gasket (flat
washer) on the injector, using hand force to
push it over the tip and down until it is fully
seated against the bottom of the injector. DO
NOT use grease or any other material to
secure the gasket to the injector; the gasket
must be installed dry. Three small
projections (grippers) on the inside diameter
of this gasket retain it to the injector during
installation.
Some early production MP7 US07 engines used
the original design copper sleeves with integral
“raised bead” at the bottom of the copper sleeve.
This design does NOT use a gasket (flat washer)
between the injector tip and the copper sleeve.
These original raised-bead design copper
sleeves can be identified by a single groove, or no
groove at all around the upper circumference.
The current production “flat-bottom” design
copper sleeves, which require the gasket (flat
washer) at the injector tip, can be identified by
two grooves around the upper circumference of
the sleeve.
284
Figure 284 — Injector Nozzle Gasket
A revised gasket (flat washer) having a thin black
rubber coating for improved sealing was
implemented in production beginning mid-August
2008. Service replacement gaskets now have the
rubber coating. DO NOT remove the rubber
coating.
The gasket (flat washer) is preassembled on new
injectors.
9. Slip the injector hold-down yoke and a new
screw of correct length onto the unit injector.
1. Unit Injector Sealing
Plug, 9998251
2. Unit Injector Bore