Land Rover Injection Pump Bosch Manual

							Robert Bosch type VE Diesel injection pump http://www.cs.rochester.edu/u/jag/vw/engine/fi/injpump.html
1 of 32/25/2009 3:02 PM
Robert Bosch type VE Diesel injection pump 
For many home mechanics the
diesel injection pump is a bit of a
mystery. The Bentley and Haynes 
repair manuals doesnt describe its
internals, because its not 
serviceable except by a few diesel
specialists. Learning some basics 
of how it works and what its
internals are could be of interest to 
the diesel owner, and the
knowledge certainly cant hurt 
when troubleshooting fuel injection
problems, even if one isnt about to 
take the pump apart.
The purpose of the fuel injection
pump is to deliver an exact metered
amount of fuel, under high 
pressure, at the right time to the
injector. The injector, unlike in a 
gasoline engine, injects the fuel
directly into the cylinder or a 
prechamber connected to the
cylinder.
The VE in the name of the Bosch pump used in the VW diesels and many other small diesel engines stands
for Verteiler, which is German for distributor or divider. The other common kind of injection pump is the
inline pump. The difference between them is that the Verteiler VE pump has one fuel metering plunger,
and a mechanism (the Verteiler/distributor) to send the fuel to the right cylider. The inline pump has one
plunger for each cylinder.
The Bosch VE
has 
comparatively 
few moving 
parts, but what 
does move does
so in a complex 
way. The figure 
to the left is from 
a Yanmar pump,
which works and 
looks the same as 
the Bosch . On 
the leftmost end
in the picture is 
the fuel feed 
pump. This is a  
						

							Robert Bosch type VE Diesel injection pump http://www.cs.rochester.edu/u/jag/vw/engine/fi/injpump.html
2 of 32/25/2009 3:02 PM
vane pump, just 
like the vacuum
pump on the VW 
diesel engine. Its purpose is to suck fuel from the tank and deliver it to the metering pump. All the things
shown on the right in the figure have to do with the metering, timing and distribution of fuel delivery. The
figure below shows this part in detail.
The plunger (right
middle in the figure) in 
the VE pump both 
rotates along its axis
and performs a
reciprocating 
translation in and out. It 
is the translation that
performs the high 
pressure pumping, 
while the rotation is 
responsible for
metering and sending 
the fuel to the correct 
cylinder.
The cam disk is rigidly
attached to the plunger. 
The drive shaft rotates
the cam disk. The cam 
disk rides on four 
rollers (only one shown in this picture), and has four lobes. Thus for each revolution the plunger will pump
four times. Note that with this arrangement the plunger stroke is constant. The metering (regulation of how
much fuel is delivered) is done not by changing the mechanical stroke, but by spilling some of the fuel
through spill ports, and thus changing the effective stroke . This is done by uncovering a spill port under the 
control sleeve at a particular angle of rotation. The other purpose of the rotation is to deliver the fuel to the
correct cylinder. This is done by having four four delivery valves (only one shown in the figure), one for
every 90 degrees of rotation. During a full revolution the plunger makes four strokes, one at 0, 90, 180 and
270 degrees. During each stroke the delivery port in the middle of the plunger is connected to a particular
delivery valve.
To understand the function in some detail lets consider one stroke. During the backward motion of the
plunger, the rotation uncovers a fill port (to the right in the figure, just below the magnet valve (solenoid)),
and the plunger barrel is loaded with fuel. At bottom dead center the fill port is closed. On the forward
pressure stroke fuel is pressurized (to over 120 bar). At this time the Plunger barrel is connected to a
particular delivery valve through the channel in the center of  the plunger, and a port in the side. When
pressure builds up to the delivery valve opening pressure, the valve will open and deliver high pressure fuel
to the injector.
When the desired amount of fuel has been injected the spill port opens (located under the control sleeve in
the figure), and the pressure quickly drops. This causes the delivery valve to close. During the rest of the
stroke fuel is spilled through the spill port instead of being injected into the cylinder.
The position of the control sleeve controls at what angle the spill port opens, and thus determines the
amount of fuel injected, in other words it controls the metering. The control sleeve is moved in response to a 
						

							Robert Bosch type VE Diesel injection pump http://www.cs.rochester.edu/u/jag/vw/engine/fi/injpump.html
3 of 32/25/2009 3:02 PM
combination of accelerator position and engine speed. The latter is determined by a mechanical governor.
Other functions 
Some other functions of the fuel injection pump are:
Timing The timing is adjusted in response to engine RPM. At higher RPM s, the fuel pressure from
the vane transfer pump is higher. Pressure changes effects a spring loaded plunger, and the resulting
movement will move the cam rollers to either advance or retard the timing. There is also a cold start
device which advances the idle timing manually.
Governor A mechanical governor limits the maximum speed of the engine to 4800 rpm in the
bus/vanagon application and 5350 rpm in newer passenger cars. It can be seen just above the cam disk
in the middle figure.
Stop A magnet valve or solenoid (shown in the figures) opens and shuts off the fuel channel between
the feed pump and the metering pump.
Aneroid An air inlet pressure sensor is used to determine maximum amount of fuel delivered on
injection pumps for turbo engines. On newer (89 and later) naturally aspirated engines a similar
arrangement is used for altitude compensation.
Misc. Internet postings about the diesel fuel injection
Martin Jägersand                 Comments?