Stop Solenoid; Cold Start Device - Yanmar 3TNV82A-B Service Manual

Introduction

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.
TNV DI Service Manual
Electronically controlled engines 4TNV84T-Z,
4TNV98-Z, 4TNV98-E, and 4TNV98T-Z are
designed so that, when the key is turned on or off,
the corresponding signal is sent to the E-ECU.
Thus the E-ECU controls the rack actuator to
provide a sufficient injection rate when the engine is
started up (the key is turned on) or cut the fuel
supply and stop then engine when the key is turned
off. Therefore, these electronically controlled
engines does not have a stop solenoid.

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.
Electronically controlled engines 3TNV84T-Z,
4TNV84T-Z, 4TNV98-Z, 4TNV98-E, and
4TNV98T-Z use a cold start device (CSD) that
consists of a fuel injection pump complete with a
solenoid valve (Figure 7-2, (1)).
FUEL SYSTEM
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