Operation - MCi MC8 Crusader Maintenance Manual

MAINTENANCE
Crusader
MC-8
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MANUAL
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Figure 4 - 7: Unloader Mechanism
UNLOADER MECHANISM: The unloader
pistons and their bores must be lubricated with
special lubricant (dimethyl polysiloxane) prior to in-
stallation. If new unloader kits are being installed,
the pistons in the kit are already lubricated.
Install the unloader pistons in their bores with
caution against cutting the grommets or distorting the
back-up rings. Position unloader plungers in their
g1;1ides and slip them in and over the tops of the
pistons.
Install the unloader spring seat in the cylinder
block; a small hole is drilled in the block for this pur-
po~e. Pos~tion the saddle between unloader piston
guides so its forks are centered on the guides. Install
the unloader spring making sure it seats over the
spring seats both in the block and on the saddle.
Install inlet valve seats if they have been previously
removed. Position and install inlet valve guides, then
drop inlet valves in their guides. There should be a
loose sliding fit between guides and valves.
CYLINDER HEAD ASSEMBLY: If previously
removed, the discharge valve seats should be in-
stalled. Drop discharge valves into their seats. Install
discharge valve springs and cap nuts.
Place the inlet valve springs in the cylinder head.
~se a small quantity of grease to hold them in place,
JUst enough grease to keep the springs from falling
out. Place cylinder head gasket on cylinder block.
Carefully align cylinder head assembly on block and
install cap screws with lockwashers. Tighten securely
and evenly cap screws that hold cylinder head to
block.
GOVERNOR (TYPE D-2)
DESCRIPTION
The governor, operating in conjunction with the
compressor unloading mechanism, automatically
controls the air pressure in the air brake or air supply
system between the desired, predetermined maximum
and minimum pressures. The compressor runs con-
tinually while the engine runs, but the actual com-
pression of air is controlled by the governor which
stops or starts compression when the maximum reser-
voir pressures are reached. The D-2 governor has a
piston upon which air pressure acts to overcome the
pressure setting spring and controls the inlet and
exhaust valve to either admit or exhaust air to or
from the compressor unloading mechanism.
OPERATION
Reservoir air pressure enters the D-2 Governor at
its reservoir port and acts on the area of the piston
and beneath the inlet and exhaust valve. As the air
pressure builds up the piston moves against the
resistance of the pressure setting spring. The piston
and inlet and exhaust valve move up when the reser-
voir air pressure reaches the cut-out setting of the
governor. The exhaust stem seats on the inlet and
exhaust valve and then the inlet passage opens.
Reservoir air pressure then flows by the open inlet
valve, through the passage in the piston and out the
unloader port to the compressor unloading
mechanism. The air, besides flowing to the com-
pressor unloading mechanism, also flows around the
piston and acts on the additional area of the piston.
This additive force which results from a larger area
on the piston assures a positive action and fully opens
the inlet valve.
As the system reservoir air pressure drops to the
cut-in setting of the governor, the force exerted by
the air pressure on the piston will be reduced so that
the pressure setting spring will move the piston down.
The inlet valve will close and the exhaust will open.
With the exhaust open, the air in the unloader line
will escape back through the piston through the
exhaust stem and out the exhaust port.
MAINTENANCE
After 15,000 miles, clean or replace governor
filters. If cleaning, use a cleaning solvent which is
known to have no detrimental effect on metal or rub-
ber material. If filters are removed they should be
replaced with new filters.
After 100,000 miles, disassemble the governor and
clean and inspect all parts.
SERVICE CHECKS OPERATING TEST
Start engine and build up air pressure in the air
system and check the pressure registered by the dash
gauge or test gauge at the time the governor cuts out,
stopping the compression of air by the compressor.
The cut-out pressure should be approx. 115-118 psi.
maximum.
With the engine still running, make a series of
brake applications to reduce the air pressure and ob-
serve at what pressure the governor cuts-in the com-
pressor. As in the case of the cut-out pressure, the cut
in pressure should be 95-105 psi. Never condemn or
adjust the governor pressure settings unless they are
checked with an accurate test gauge or a dash gauge
that is registering accurately. If the pressure settings
of the governor are inaccurate or it is necessary that
they be changed, the procedure is as follows:
First, unscrew the cover at the top of the governor.
Next, loosen the adjusting screw locknut. With a
screwdriver the adjusting screw is turned coun-