Adjusting Injection Advance; Transfer Pump - Fiat Bravo Service Manual

Bravo-Brava
1. Fuel inlet
2. Small piston
3. Cylinder
4. Pin
5. Spring
6. Cam seal
7. Solenoid valve
8. Fuel outlet
1. Transfer pump rotor
2. Brushes
3. Eliptical seal
Copyright by Fiat Auto
ft
TD100
IX-96 - Cancels and replaces

Adjusting injection advance

The injection advance adjustment system
makes it possile to vary the start of the injec-
tion so that it takes place at the optimum time
in all engine operating conditions.
The system comprises a small piston (2)
w h i c h slides in the cylinder (3) and is o p -
posed by the spring (5).
This piston is connected to the cam seal (6)
by means of a threaded pin w i t h a spherical
head ( 4 ) .
If the solenoid valve (7) is not activated, the
transfer pressure ( 1 ) , acting on the piston
( 2 ) , moves the actual piston overcoming the
resistance of the spring (5) and causes the
rotation of the cam seal ( 6 ) , through the pin
( 4 ) , in relation to the pump control shaft, t o -
wards the maximum advance position.
The activation of the solenoid valve (7) al-
lows the fuel to flow towards the vehicle tank
via the return pipe (8). This causes a de-
crease in the pressure acting on the piston
(2) allowing the spring (5) to extend fully
and, rotate the cam seal towards the mimini-
mum advance position by means of the pin
(4).
In this way by varying the solenoid valve (7)
opening/closing frequency, the
control unit modulates the value of the pres-
sure acting on the piston (2) thereby contin-
uously regulating the start of the injection.

Transfer pump

The transfer pump, which is the volumetric
type (inlet and pressure), consists of a rotor
( 1 ) , an eliptical seal (3) and t w o rigid brush-
es ( 2 ) .
During rotation, the brushes (2) slide in the
rotor (1) following the profile of the eliptical
seal (3) w h i c h is offset in relation to the rotor.
As the volume in the chamber increases, a
vacuum is created upstream of the blade w i t h
the consequent intake of fuel from the tank;
the volume decreases downstream of the
vane and consequently the fuel in the circuit
is supplied under pressure.
E n g i n e
Fuel system
10.
electronic
9