FUEL SYSTEM
TNV IDI Service Manual
7-5
Introduction
NOTICE
• NEVER remove or attempt to remove the tamper-
proof devices from the full-load fuel adjusting
screw or the high-speed throttle limit screw on the
fuel injection pump and governor assembly.
These adjustments have been made at the
factory to meet all applicable emissions
regulations and then sealed.
• NEVER attempt to make any adjustments to
these sealed adjustment screws. If adjustments
are required, they can be made only by a
qualified fuel injection shop that will ensure the
injection pump continues to meet all applicable
emissions regulations and then replace the
tamper-proof seals.
• Tampering with or removing these devices may
void the “Yanmar Limited Warranty.”
The fuel injector is essentially a spring-loaded
valve. When fuel pressure from the fuel injection
pump reaches a pre-determined level, the pintle
(valve) is forced off its seat and fuel is atomized as
it passes between the pintle and seat. The timing
and quantity of the fuel injected into the cylinder is
controlled by the fuel injection pump and governor
assembly.
Stop Solenoid
The ML 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 the 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, and 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
or the engine 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 VOA multimeter or continuity
light to check for a good ground and 12V at the stop
solenoid in the correct sequence.
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