Yanmar 4TNE98, Service Manual

Page: 144 / 246

4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System 142
Stop Solenoid
The MP fuel injection pumps are equipped with a
stop solenoid that controls the fuel flow inside the
fuel injection pump.
With the starter switch in the OFF position, no
current flows to the stop solenoid and the solenoid
plunger is extended holding the fuel injection pump
fuel rack in the “closed” position and not allowing
fuel to flow through the injection pump and to the
engine.
When the starter switch is turned to the start
position, the “pull coil” (36.5 Amp draw/white wire)
inside the solenoid is activated and pulls the
solenoid plunger into the solenoid. This releases
the fuel injection pump fuel rack, allowing fuel to
flow through the injection pump and allowing the
engine to start and run.
When the starter switch is returned to the ON or
RUN position, the “pull coil” no longer receives
current and the “hold coil” (0.5 Amp draw/red wire)
inside the solenoid is activated. The “hold coil”
holds the solenoid plunger in the RUN position,
allowing fuel to continue flowing and he engine to
continue running.
To stop the engine, the key switch is turned to the
OFF position. Current no longer flows to the stop
solenoid “hold coil”, and the solenoid plunger
extends and moves the injection pump fuel rack to
the “closed” position, shutting off the fuel flow and
stopping the engine.
Failure of the stop solenoid could result in the
engine not starting, the engine stopping suddenly,
the engine not continuing to run with the key switch
returned to the ON or RUN position, or the engine
failing to stop when the key switch is turned to the
OFF position. Use a multimeter or continuity light to
check for 12V at the stop solenoid connector in the
correct sequence.
Cold Start Device
The Yanmar TNV model engines are equipped with
a cold start device (CSD).
The cold start device is located in the upper section
of the fuel injection pump and is connected to the
engine’s cooling system.
• The cold start device improves engine starting at
lower temperatures. At engine cooling system
temperatures below 41°F (5°C), the cold start
device advances the fuel injection timing and
slightly increases the fuel injection volume.
• For approximately the first 5 minutes of operation,
the idle speed of the engine will be slightly
elevated.
CAUTION
Allow the engine to warm-up for at least five
minutes and the idle speed of the engine to
return to normal before engaging the
transmission or any PTOs. Engaging the
transmission or PTO at an elevated engine
speed could result in an unexpected movement
of the equipment.
• When the cold start device is activated, you may
notice a slight increase in the exhaust smoke of
the engine during engine warm-up.
Trochoid Fuel Pump
NOTE: The trochoid fuel pump located on the side
of the MP fuel injection pump is not a “fuel supply”
pump. The function of this pump is to raise the
pressure of the fuel supplied by the electric fuel
supply pump to the internal fuel pressure required
by the MP fuel injection pump.
The use of an electric fuel supply pump is required
on all TNV model engines with the MP fuel injection
pump.