IMPACT 4.04.
00 11/04/2023
Chassis ID Path
A 776867 23/Description, Design and function//Fuel system, system description
Model Identity
FM (4) 143351836
Publish date ID/Operation
27/10/2018
Fuel system, system description
Fuel system
Fuel system, overview
Fuel feed system, principle
Fuel system, components
Unit injector
Fuel tank
Fuel tank, equipment
Fuel system
Fuel system, overview
The illustration shows the main components of the fuel system.
Fuel system, components
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
1/7
IMPACT 4.04.00 11/04/2023
1 Strainer, combined tank unit
2 Feed pump
3 Fuel filter housing
4 Primary filter with water separator
5 Air vent valve
6 Fuel filter
7 Overflow valve
8 Unit injector
9 Fuel channel in the cylinder head
10 Cooling coil for the engine control unit
The fuel system is controlled electronically via the ECM (Engine Control Module). The fuel is injected
at high pressure by unit injectors, one for each cylinder. This high pressure is created mechanically
via the overhead camshaft and rocker arms. Fuel volume and injection timing are regulated
electronically via the ECM, which receives signals from a number of sensors.
The fuel system is equipped with a hand pump, which is located on the fuel filter housing.
Fuel feed system, principle
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
2/7
IMPACT 4.04.00 11/04/2023
Fuel is drawn up using the feed pump (1) through the strainer (2) in the combined tank unit, up
through the cooling coil (6) , which cools the engine control unit (16) , and then down to the fuel filter
housing (3) . There, the fuel passes a non-return valve (11) and primary filter (4) with water separator
(13) . The non-return valve prevents fuel flowing back to the tank when the engine is turned off and
when pumping by hand.
The feed pump (1) forces fuel to the fuel filter housing (3) and through the main filter (5) up to the
longitudinal fuel channel in the cylinder head (9) . This channel provides each unit injector (8) with
fuel via a ring-shaped space around each injector. The overflow valve (7) regulates the fuel feed
pressure to the injectors.
Return fuel from the fuel channel in the cylinder head (9) flows via the overflow valve (7) back to the
fuel filter housing (3) . The return fuel is mixed with fuel from the tank in the channel running through
the fuel filter housing and drawn on to the feed pump inlet (suction side).
There are two valves in the feed pump. The safety valve (14) allows fuel to flow back to the suction
side when the pressure is too high, for example, due to a clogged fuel filter. The non-return valve (15)
opens when the manual fuel pump (12) is used, to facilitate its use.
The fuel filter housing (3) also contains an air vent valve (10) . The fuel system is vented
automatically when the engine is started. Any air in the system flows back to the fuel tank (2) together
with a small amount of fuel.
When changing a filter, the valve pegs (18) and (19) close, which prevents fuel from leaking out when
the fuel filter is unscrewed. The new filter is vented using the valves (18) and (20) in the filter housing
and the air vent valve (10) .
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
3/7
IMPACT 4.04.00 11/04/2023
There is a fuel pressure sensor (21) on the fuel filter housing, which measures the feed pressure after
the fuel filter. An error code is shown on the instrument panel if the feed pressure is below the value
specified in the error code manual. The plugged outlet (22) on the fuel filter housing is used for
measuring feed pressure with an external pressure sensor.
A level sensor (23) in the water separator (13) indicates the presence of water in the system to the
driver. Buttons (24) on the steering wheel are used for draining. These open an electric drain valve (
25) via the engine control unit.
For the draining process to start, the following conditions must be met:
● The level sensor (23) in the water separator indicates high water level.
● The engine is turned off/key in drive position.
● The vehicle is stationary.
● The handbrake is applied.
Draining stops if the engine is started during the process. The warning remains on the instrument
panel as long as the "water in fuel" indicator is above the warning level. A fuel heater (26) for
installation in the bottom of the water separator is available as extra equipment.
The hand pump (12) on the fuel filter housing is used to pump fuel (with stationary engine) when the
fuel system is being emptied.
Note
Do not use the hand pump when the engine is running.
Fuel system, components
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
4/7
IMPACT 4.04.00 11/04/2023
(A) : The unit injectors are the E3 type with two solenoid valves.
(B) : The hand pump (1) in the fuel filter bracket is used to pump fuel when the system is empty, and
a non-return valve prevents fuel flowing back to the tank when the engine is shut down. The electrical
connection (2) is for the level sensor (3) and the drain valve (4) in the water separator (5) . The
primary filter (6) filters the fuel before it enters the feed pump, i.e. on the suction side. The main filter (
7) filters the fuel after the feed pump, i.e. on the pressure side. The fuel system has an air vent valve
(20) located on the fuel filter bracket.
(C) : The fuel feed pump is a gear pump located on the steering servo pump (8) . The feed pump is
driven by the shaft through the steering servo pump (9) . An O-ring (10) in a groove in the steering
servo pump flange seals between the two pumps. Power transmission between the pumps is via a
floating dog (11) . The pump housing (12) and end piece (13) are in cast iron. The drive-rotor shaft
and the driven rotor are mounted in needle bearings (14) and (15) . The pump safety valve (16) is
located in the pump housing and the non-return valve (17) in the pump end piece. Fuel leaking
passed the pump drive shaft is drawn back to the suction side of the pump via the channel (18) .
(D) : The cooling coil on the left-hand side of the engine cools the ECM with fuel from the suction side
of the feed pump.
(E) : The overflow valve (19) on the cylinder head regulates the pressure in the low pressure system,
which supplies fuel to the unit injectors while also cooling them. The overflow valve has an integrated
air vent valve for the fuel system.
Unit injector
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
5/7
IMPACT 4.04.00 11/04/2023
The unit injector is located vertically above the centre of each cylinder, between the four valves, and
secured in the cylinder head by a yoke (1) . The lower part of the injector is separated from the
coolant jacket by a stainless steel tapered sleeve (2) . The circular space for fuel supply (3) around
each injector is sealed with two O-rings (4) ,(5) .
In principle, a unit injector can be divided into three main parts:
(A) Pump
(B) Valve (Actuator)
(C) Nozzle
The valve part contains two solenoid valves - spill valve (6) and needle valve (9) with solenoid coils (7
) and (8) respectively, and return springs.
During the filling phase, the pump piston moves up and fuel from the cylinder head fuel channels is
forced into the unit injector.
During the spill phase, the pump piston moves down and fuel is forced back out to the cylinder head
fuel channels. When the solenoid coils are not energised and the spill valve is open, no pressure can
build up in the fuel channel to the nozzle.
During the pressure build-up phase, the spill valve solenoid coil is energised and the spill valve
closes. A high pressure then builds up in the fuel channel (12) . A high pressure also builds up in the
chamber (13) behind the needle valve, which impacts on the needle valve piston (10) and prevents
the needle valve (9) from opening the nozzle (11) .
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
6/7
IMPACT 4.04.00 11/04/2023
The injection phase occurs once the required pressure has been attained. The needle valve solenoid
coil is energised and opens the needle valve (9) . The high pressure is then released onto the needle
valve piston and the nozzle (11) opens. Atomised fuel is sprayed at very high pressure into the
engine combustion chamber.
Fuel injection is interrupted when the spill valve opens again, whereby the pressure on the piston (10)
drops and the nozzle (11) closes. The whole injection sequence is controlled by the ECM.
There are three markings on the electrical connection (14) - part number (15) , trim code (16) and
serial number (17) . When replacing one or more injectors, the engine control unit must be
programmed to the trim code of the new injectors as each unit injector is unique and the engine is
tuned for optimum fuel injection and as little emission as possible. The trim code is programmed
using parameter programming in the diagnostic tool (Volvo Tech Tool).
Fuel tank
Fuel tank, equipment
There is a kit available for the fuel tank filler, comprising of a lockable fuel cap (A) , anti-spillage
device (B) and anti-siphoning device (C) .
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
7/7
