FUEL SYSTEM
7-8
TNV DI Service Manual
Introduction
INTRODUCTION
This section of the Service Manual describes the
procedures necessary to remove, install, and time
the MP fuel injection pump and its associated
system components. This fuel injection pump is
representative of the fuel injection pumps used on
other TNV DI model engines. The descriptions
given in this section basically apply also to fuel
injection pumps used for electronically controlled
engines unless otherwise described herein.
Fuel Injection Pump
Note: If the MP fuel injection pump itself
requires servicing, it must be taken to an
authorized Yanmar FIE (Fuel Injection
Equipment) repair facility.
Figure 7-1
The following describes the features of the MP fuel
injection pump, manufactured by Yanmar.
The fuel injection pump is a very important
component of the engine. It is capable of making
very precise fuel delivery adjustments according to
the varied loads applied to the engine.
All of the fuel injection pump components are very
precisely machined. It is extremely important to
follow good service practices and maintain
cleanliness when servicing the fuel injection pump.
The Yanmar MP “Mono-Plunger” Fuel Injection
Pump is a distributor type pump which consists of a
single fuel supply plunger, a distributor shaft, a
hydraulic head and a pump housing. The hydraulic
head has a delivery valve for each cylinder. The
fuel injection pump housing contains a governor
and an internal camshaft.
The fuel is pressurized by the up and down motion
of the camshaft-driven single plunger. It is then
distributed to the proper fuel injector by the rotating
distributor shaft.
There are two versions and sizes of the MP Fuel
Injection Pump. The smaller of the two pumps, the
MP2 pump, is used on the 3TNV82A - 4TNV88
model engines. The larger pump, the MP4 pump,
which has a larger single plunger and a more
aggressive cam profile, is used on the
4TNV94L - 4TNV106T model engines.
CAUTION
• 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.”
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