Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea Weekend
ft Engine
99 update Fuel system
10.
CHECKS, ADJUSTMENTS AND REPAIR OPERATIONS ON THE HITACHI MPI SYSTEM
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The following precautions must be observed when working on a vehicle equipped with a Hitachi
MPI system:
do not start the engine when the electrical leads are not properly connected or are slack at the
battery terminals;
- do not use a rapid battery charger to start the engine;
- never disconnect the battery from the electrical system with the engine running;
- when recharging the battery, it must be disconnecte first from the electrical system;
- if the vehicle is going into a drying oven after painting at temperatures above 80"C, then the en-
gine management control unit must be removed from the vehicle first;
- do not connect/disconnect the control unit multiple connector with the ignition switched ON;
- always disconnect the negative battery lead before carrying out electrical welding on the vehicle.
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The system has a memory which is supplied directly by the battery, even when the ignition is
switched off, where the values acquired during the self-adjustment are stored. The operation of
disconnecting the battery means that this data is lost and can only be acquired again after a cer-
tain length of time: this operation should therefore be carried out as infrequently as possible.
NOTE If the Hitachi MPI sysetm components are replaced:
- Butterfly casing and flow meter
- Engine idle speed actuator
- Butterfly position sensor
- Engine management control unit
- Lambda probe
The negative battery terminal must be disconnected in order to reset the self-adjustment memory
which could, with new components, involve the failure of the engine to start or the irregular be-
haviour of the engine when first started.
CHECKING CONCENTRATION OF EMISSIONS
The system manages the advance, the carbon monoxide (CO) content and the idle air flow rate without
any possibility of manual adjustment.
However, a check on the content of the exhaust gases, upstream and downstream of the catalyzer, can
provide useful information on the injection/ignition system operating conditions, the engine parameters
and the catalyzer.
Checking idle concentration of CO and HC upstream of the catalytic silencer
To check the concentration of carbon monoxide (CO) and unburnt hydrocabons (HC) upstream of the
catalyzer, proceed as follows:
1. Undo the cap located 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 idle 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 wear of the spark plugs).
6. In the same conditions, check that the concentration of HC is below 500 p.p.m.
7. If the values do not correspond, tune the engine, checking, in particular:
- the valve gear timing;
- the engine compression.
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