Dacia Pick-Up 1304/1305/1307. Service manual — part 35
IGNITION AND INJECTION
17
17 - 4
The components of the injection system are: (drawing no.1).
1
- Fuel electric pump
3
- Fuel filter
4
- Fuel pressure regulator
5
- Injector
6
- Air temperature sensor
8
- Valve position potentiometer
9
- Idle motion regulator
10
- Carbon canister purging valve
11
- Active carbon canister
12
- Electronic control unit ( computer for injection and ignition ).
13
- Induction coil
14
- Engine sensor T
15
- Rotation sensor
16
- Oxygen sensor ( Lambda ).
17
- Catalytic convertor
18
- Ignition control cables with plug for system diagnosis
The drawing also indicates 2 – Fuel tank, 7 – Air filter.
The fuel supply circuit consists of tank fuel electric pump, fuel filter, injection central
unit, supply and back-feed pipes.
Central unit
( injector valve body )
DESCRIPTION OF THE SYSTEM
DESCRIPTION OF THE SYSTEM AND ITS COMPONENTS
17
IGNITION AND INJECTION
17 - 5
1
- The upper part (hydraulic part)
2
- The lower part (body-valve)
3
- Pressure regulator
4
- Injector
5
- Air sensor T
6
- Fuel input ( supply connection ).
7
- Fuel output ( back-feed connection )
8
- Idle motion regulator
A
= Connector for air sensor T aer and
injector.
B
= Connector for valve potentiometer.
C
= Connector for idle motion breaker and
valve positioning engine.
INJECTION CENTRAL UNIT
PRESSURE REGULATOR
It is a mechanical membrane regulator which insures an injection pressure of 0,8 – 1,15
bar, the engine being under motion.
The pressure is measured as follows:
- a T connection and a manometer of 0 – 4 bar are connected to the fuel input
connection into the valve body;
- the pump is supply by starting the engine or by shunting the terminals 30 and 87
of the relay R1, with both engine and contact OFF.
AIR TEMPERATURE SENSOR ( AIR T )
The air T sensor (5) – (drawing 4) measures the temperature of the air sucked by the
engine.
Knowing that the air density decreases with the temperature increasing, the electronic
control unit will correct the injection time (t
i
), in order to maintain the report air/fuel at
optimal values.
The air sensor T is a NTC type (temperature negative coefficient), which means that
its internal resistance decreases with temperature increase. It is supplied with U = 5 V
(pin 13, computer).
Reference values: R = 1450 – 3300 Ù at 15 – 30 °C
R = 2500 ± 125 Ù at 20 °C
The injection central unit consists of:
Fig. 2
DESCRIPTION OF THE SYSTEM
IGNITION AND INJECTION
17
17 - 6
INJECTOR
The injector (drawing 4) is placed above the valve in order to ensure an optimal supply
and homogenous mixture of the fuel. The injector basic function is to ensure a very fine
and homogenous spraying of the fuel, shaped as a conic jet. This fuel is sprayed through
the half-moon gap between the valve and the wall, without hitting the latter, as it happens
in case of a straight spraying (carburetor).
For an exact dosing of fuel quantity we use the light component of the injector (its
moving needle), which ensures a rapid movement. Being permanently washed in fuel, it
avoids its heating and the fuel bubbles.
The electronic unit (pin 35) controls the injector functioning.
The injection time (t
i
) is the while the injector is opened and it is the most important
value of the injection system.
The injection time (t
i
) depends upon the voltage accumulator battery; if there are
voltage fluctuations during the functioning, the electronic control unit will correct the
injection time for an air-fuel optimal report (ë = 1).
In case of a low voltage at start the value (t
i
) should be increased in order to compensate
the lower flow of the fuel electric pump.
The simple testing of the injector is done by means of stroboscopic lamp. The air pipe
above the injection unit is to be dismounted, the engine is to be started and the spraying
cone of the fuel is watched by means of the stroboscopic lamp. The upper part (hydraulic
part) of the injection central unit is not to be repaired – the whole injector-valve-body
system is to be replaced.
In case of damaging the injector or the air sensor T, both of them are to be replaced.
The connector between the air sensor T and
the injector has the following connections:
1
- Air sensor T ( pin 13 computer )
2
- Injector supply ( + )
3
- Injector control ( pin 35 computer )
4
- Mass ( pin 27 computer )
The oscilloscope checks the injector
functioning; it is to be connected according
to the position “A”, namely mass parallel. It
is not to be connected as in position “B”,
which will affect the transistor, leading to
errors of signal.
+ APC
DESCRIPTION OF THE SYSTEM
17
IGNITION AND INJECTION
17 - 7
A sign shaped as follows will be displayed
on the oscilloscope screen. It is to be used for
the calculation of the injection time = t
i
.
The injection time value increases when
the battery voltage is lower than 12 V.
Reference values for the injector:
- resistance measured between the wires 2
and 3, R
2-3
= 6.3 - 7.4 Ù
- a maximum of 1 fuel drop at the injector/
1 minute is visually checked and admitted
when supplying the fuel pump by shunting
the terminals 30 and 87 of the relay R
1
, with
lose contact.
VALVE POTENTIOMETER
The valve potentiometer (drawing 4, position B) is fixed on the injection unit at the
end of the valve axle and consists of a potentiometer a double way. This is supplied with
+ 5 V from the pin 25 computer and sends to the later a voltage signal proportional with
its position. Then the computer will control the injector and the induction coil.
The potentiometer consists of:
1
- Mass
2
- Potentiometer I
3
- Potentiometer II
4
- Supply ( + )
5
- Brushes
6
- Insulator
DESCRIPTION OF THE SYSTEM
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