TROUBLESHOOTING
Page 83
4. Check for oil leaks at the oil supply screw,
solenoid valve and housing pipe plugs. If
leakage is noticed, shut down the engine
and repair the leaks.
Some leakage will be seen at the master piston,
slave piston and control valves. This is normal.
Excessive leakage must be investigated (see
Hydraulic/Mechanical Troubleshooting).
5. After final inspection and necessary repair,
shut down the engine and replace the
gaskets and covers.
6. Test drive the vehicle following the Test
Drive procedures (covered earlier) to verify
corrective action.
Troubleshooting Guide
Following is a listing of problem conditions
showing the probable causes and subsequent
corrections.
ENGINE FAILS TO START
r Solenoid valve stuck in ON position —
Ensure that electrical current is off to the
engine brake units. If the solenoid valve
remains on (cap down) with current off,
replace the solenoid valve.
ENGINE BRAKE WILL NOT OPERATE
r Blown fuse, open electrical leads — Look
for a short circuit in the wiring. Replace any
broken, brittle or chafed wires. Check
solenoid tab for signs of shorting and
replace if necessary. Replace 10 amp fuse.
r On/Off switch, clutch switch or multi-
position switch out of adjustment or
defective — Use a volt/ohm meter to make
certain that there is electrical voltage
available at both terminals of each switch.
Readjust if needed or replace if voltage will
not pass through switch.
Do not touch electrical connection when
system is energized.
r Incorrect electrical power source —
Check that the supply voltage is the
appropriate voltage. Recommended power
source is from the key switch ON position.
Ensure that power is not taken from a
source with an additional on/off switch, i.e.,
light switch. See solenoid specifications in
the Table on page 80. Make sure wiring is in
accordance with MACK wiring instructions.
r Low engine oil pressure — Determine oil
pressure at engine brakes (solenoid valve
and control valve); see oil pressure
requirements in the Table on page 80. If oil
pressure is below specification, the engine
should be repaired in accordance with
MACK procedures.
r Slave lash not properly adjusted — The
model 690 engine brake is very sensitive to
adjustment. Incorrect adjustment may hold
the valves open during positive power,
leading to engine failure, or may cause the
engine brake to work poorly or not at all.
Confirm that the engine brake is properly
adjusted in accordance with the Table on
page 80.
ENGINE BRAKE DOES NOT OPERATE AT
LOW ENGINE RPM
r Inlet check valve leaking — Early-
production engine brake housings contained
a check valve (with ball, spring, retaining
ring and washer) assembled into the
housing. In June 2000, the housing’s internal
check valve components and hollow oil
supply screw were replaced by a new oil
supply screw containing an integral check
valve. If the housing contains the early-
production internal check valve components
and a hollow oil supply screw, remove the
check valve components (ball, spring,
retaining ring and washer) from the housing
and replace the hollow oil supply screw with
the current-production screw containing an
integral check valve.
5_106_00.bk Page 83 Friday, August 4, 2000 11:17 AM
BDC for engine manuals and specs
https://barringtondieselclub.co.za/
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