Mack MP7 - Page 129

Page 118
REPAIR INSTRUCTIONS, PART 1
Three different styles of the unit injector
hold-down yokes were used in production on
MACK MP engines. The first style (1) is 28 mm
tall with a pronounced stepped-down area on the
end of the yoke that engages the unit injector.
The second style (2) is 38 mm tall, and the end of
the yoke that engages the unit injector is not
stepped-down. The third style (3) is also 38 mm
tall, but the end that engages the unit injector is
stepped-down to allow the forks of the heavy-duty
unit injector puller (tool No. J 48922) to engage
the unit injector groove. This allows removal of
the unit injector without necessitating the removal
of any valve springs.
121
Figure 121 — Unit Injector Hold-Down Yoke Styles
When replacing 28 mm height injector yokes with
38 mm height yokes, all six yokes must be
changed to the current 38 mm height
components. NEVER replace a 38 mm height
yoke with a 28 mm height yoke. Once an engine
has the new design 38 mm height yoke, either
from the OEM or field installation, it must stay
with the new design 38 mm high yoke at all
cylinder locations.
4. Using the chart below to determine the
correct method of unit injector removal
based on the status of the injector
(immovable [stuck], or removable [not
stuck]), remove the unit injector as described
in the following steps for the style of
hold-down yoke being serviced:
Unit Injector Status
28 mm (Short)
Yoke
38 mm (Tall)
Yoke
38 mm (Tall)
Yoke with
Stepped-Down Area
Unit Injector — Immovable (Stuck) Heavy-Duty Puller
J 48922
Heavy-Duty Puller
J 48922
NOTE: Requires removal
of the inlet and exhaust
valve springs to allow
access for heavy-duty
puller.
Heavy-Duty Puller
J 48922
Unit Injector — Removable (Not Stuck) Standard Puller
9990006
Pry Bar
9998511
Standard Puller
9990006