Mack E7, Service Manual

Page: 143 / 303

200 BENCH PROCEDURES
Page 5-53
18. Connect jumper wire to Dynatard engine
brake harness connection.
19. Attach wire tie around jumper wire and
Dynatard switch bracket.
20. Test engine brake and check for leaks.
INSTALLATION (V-MAC APPLICATIONS)
1. Connect engine brake wiring harness to
connection located on right-hand side
engine harness.
2. Secure connection to air compressor coolant
line with wire tie.
3. Secure engine brake wiring to a clamp
located on cylinder block near rear of
injection pump.
4. Test engine brake and check for leaks.
[266] JACOBS ENGINE
BRAKE
E7 engines built from mid-year 1993 through
December 1993 were equipped with either a
Dynatard engine brake or a Jake Brake. Since
January 1, 1994, the Jake Brake has been used
exclusively.
The Model 680B Jake Brake engine retarder is a
vehicle-slowing device designed and approved
for use on MACK E7 engines. Energizing the
Jake Brake effectively converts a power-
producing diesel engine into a power-absorbing
air compressor. This is accomplished by opening
the cylinder exhaust valves near the top of the
compression stroke, releasing the compressed
air to exhaust.
Releasing compressed air to exhaust prevents
the return of energy to the engine piston on the
power stroke. The result is a net energy loss used
to slow the vehicle. For more detailed
information, specifications and repair procedures,
refer to the appropriate Jacobs service manual.
[266] ENGINE BRAKE SWITCH
AND BRACKET ASSEMBLY
Description
Beginning in 1991, a cylinder block-mounted
engine brake switch and mounting bracket
assembly was released for E7 mechanically
governed (non V-MAC) engines equipped with
either a Jake Brake or Dynatard system (pre-
1994). The bracket design improves the service
life of the switch by significantly reducing the
engine vibration levels that the switch is
subjected to. This reduction in vibration levels is
accomplished by relocating the mounting of the
bracket from the rear of the injection pump to the
auxiliary housing area of the cylinder block. Refer
to Figure 5-65.
In mid 1992, an improved switch (part
No. 1MR3529) was incorporated into the
assembly. This new switch, along with relocation
of the bracket, adds significantly to the service life
of the assembly.
Proper adjustment is essential. Over-adjustment
of this switch arrangement will cause accelerated
switch wear or switch failure.
Adjustment (E7 Mechanically
Governed Engine with Engine
Brake)
1. Loosen the two screws holding the throttle
switch to the switch bracket.
2. Check the continuity by connecting a volt-
ohmmeter across the switch terminals.
3. Insert an 0.008-inch (0.203 mm) thickness
gauge between the low idle screw and the
idle lever.
4. Secure the throttle lever in the low idle
position.
5. Slide the switch toward the throttle lever to
the point where continuity is obtained.
6. Torque the two screws that hold the throttle
switch to the switch bracket to 10 lb-in using
torque wrench J 24405 or equivalent.
5-101.bk Page 53 Friday, March 17, 2006 11:05 AM