Fiat 1996 Brava Service Manual page 292

Bravo-Brava @ i ±6
V
Engine
98 range Fuel system
10.
CHECKS, A D J U S T M E N T S A N D REPAIR OPERATIONS ON THE BOSCH 1.5.5 S Y S T E M
The following precautions should be observed when working on a vehicle equipped with the
Bosch 7.5.5 system:
- do not start up the engine when the electrical connectot terminals are badly connected or
slack at the battery poles;
- do not use a rapid battery charger to start the engine;
- never disconnect the battery from the electrical system with the engine running;
- in order to charge the battery it must be disconnected first from the electrical equipment;
- if the vehicle goes in a drying oven after painting at temperatures in excess of 80 °C, it is nec­
essary to remove the engien control unit from the vehicle;
- do not connect/disconnect the control unit multiple connectors with the ignition switch in the
ON position;
- always disconnect the negative battery lead before carrying out electrical welding on the vehi­
cle.
The system has a memory which is directly supplied by the battery, even with the ignition swit­
ched off, where the self-adjustment values are stored. Disconnecting the battery will involve the
loss of this information which can only be learnt once again after a certain period: this operation
should therefore be limited as far as possible.
CHECKING E M I S S I O N S CONCENTRATION
This system manages the advance, the carbon monoxide (CO) content and the idle air f l o w rate w i t h no
possibility for manual adjustment. However, a check on the content of the exhaust gases upstream and
downstream of the catalyzer can provide useful indications on the injection/ignition system operating
conditions, the engine parameters or the catalyzer.
Checking idle concentration of CO and HC upstream of the catalytic silencer
To check the concentration of carbon monoxide (CO) and unburnt hydrocarbons (HC) upstream of the
catalyzer, proceed as follows:
1. Undo the cap located on the exhaust pipe, upstream of the catalyzer, and tighten the t o o l in its
pla ce.
2. Connect a suitably calibrated CO-tester to the tool.
3. Start up the engine and let it reach operating temperature.
4. Check that the engine speed is correct.
5. Check that the idle concentration of CO is w i t h i n the recommended values (see table); if this i s n o t
the case, check:
- that the Lambda sensor is working properly, using the diagnostic equipment;
- for the presence of air penetration in the area surrounding the Lambda sensor housing;
- the injection and ignition system ( i n particular t h e s t a t e of w e a r of t h e s p a r k p l u g s ) .
6. In the same conditions, check that the HC concentration is below 500 p.p.m.
7. If these values are not f o u n d , tune the engine, paying particular attention to:
- the valve gear timing;
- the engine compression.
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