Dacia Pick-Up 1304/1305/1307. 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

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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