Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea W e e k e n d
E n g i n e
99
range
Fuel system
CHECKS, ADJUSTMENTS AND REPAIR OPERATIONS ON THE BOSCH M1.5.5 S Y S T E M
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When working on a vehicle equipped with a Bosch M1.5.5 system, observe the following precau-
tions:
- do not start up the engine with the electrical connection terminals not properly connected or
slack at the battery poles;
- do not use a rapid battery charger for starting up the engine;
- never disconnect the battery from the electrical system with the engine running;
- to charge the battery, disconnect it first from the electrical system;
- if the vehicle has to go in a drying oven after painting at temperatures in excess of 80 °C, then
the engine control unit must be removed 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 vehicle.
The system has a memory which is directly supplied by the battery, even when the ignition is
switched off, which contains the values obtained during self-adjustment. Disconnecting the bat-
tery will mean that this information is lost and can only be acquired again after a certain length of
time: this operation should therefore be restricted as far as possible.
CHECKING THE CONCENTRATION OF THE EMISSIONS
The system manages the advance, the carbon monoxide (CO) content and the idle air flow rate without
the possibility for adjustments, threfore no manual regulations are required. However, a check on the con-
tent of th exhaust gases, upstream and downstream of the catalyzer can provide precious indications on
the injection/ignition system operating conditions, the engine parameters and the catalyzer.
Checking the idle CO and HC concentration 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 plug on the exhaust pipe, upstream of the catalyzer, and tighten the tool in its place.
2. Connect a suitably calibrated CO-tester probe 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 CO concentration is within the recommended limits (see table); if this is not the
case, it is necessary to 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
(in particular the state of the spark plugs).
6. In the same conditions, check that the HC concentration is below 500 p.p.m.
7. If these figures are not obtained, proceed with tuning the engine, in particular checking the:
- valve gear timing;
- engine compression.
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