Peugeot 405 Manual

General information
Emission control systems / General information

1 All models have various built-in fuel system features which help to minimise emissions, and all models have at least the crankcase emission-control system described below.

Models with a catalytic converter are also fitted with the exhaust and evaporative emission control systems.

2 Most models are able to run on 95 RON unleaded fuel, but the following early engines must use 97 RON leaded fuel. However it may be possible to use unleaded fuel if the ignition is retarded by 3 - check with your Peugeot dealer.

a) TU3 (K1A)
b) TU3A (K1G)
c) XU92C (D2D)
d) XU9J2 (D6A)
e) XU9J4 (D6C)
f) XU52C (B2A)
Crankcase emission control 3 To reduce the emission of unburned hydrocarbons from the crankcase into the atmosphere, the engine is sealed, and the blow-by gases and oil vapour are drawn from the crankcase, through a wire-mesh oil separator, into the inlet tract, to be burned by the engine during normal combustion.

4 Under conditions of high manifold depression (idling, deceleration) the gases will be sucked positively out of the crankcase.

Under conditions of low manifold depression (acceleration, full-throttle running) the gases are forced out of the crankcase by the (relatively) higher crankcase pressure; if the engine is worn, the raised crankcase pressure (due to increased blow-by) will cause some of the flow to return under all manifold conditions.

Exhaust emission control 5 To minimise the amount of pollutants which escape into the atmosphere, some models are fitted with a catalytic converter in the exhaust system. On all models where a catalytic converter is fitted, the system is of the closed-loop type; a lambda (oxygen) sensor in the exhaust system provides the fuel injection/ignition system ECU with constant feedback, enabling the ECU to adjust the mixture to provide the best possible conditions for the converter to operate.

6 The lambda sensor has a built-in heating element, controlled by the ECU through the lambda sensor relay, to quickly bring the sensors tip to an efficient operating temperature. The sensors tip is sensitive to oxygen, and sends the ECU a varying voltage depending on the amount of oxygen in the exhaust gases. If the inlet air/fuel mixture is too rich, the exhaust gases are low in oxygen, so the sensor sends a low-voltage signal. The voltage rises as the mixture weakens and the amount of oxygen in the exhaust gases rises.

Peak conversion efficiency of all major pollutants occurs if the inlet air/fuel mixture is maintained at the chemically-correct ratio for the complete combustion of petrol - 14.7 parts (by weight) of air to 1 part of fuel (the stoichiometric ratio). The sensor output voltage alters in a large step at this point, the ECU using the signal change as a reference point, and correcting the inlet air/fuel mixture accordingly by altering the fuel injector pulse width (the length of time that the injector is open).

Evaporative emission control 7 To minimise the escape into the atmosphere of unburned hydrocarbons, an evaporative emissions control system is fitted to later models (see illustration).

1.7 Evaporative emissions control system
1.7 Evaporative emissions control system

1 Fuel filler cap
2 Charcoal canister
3 Hose
4 Calibrated orifice
5 Hose
6 Solenoid valve
7 Coolant temperature
10 Safety valve

The fuel tank filler cap is sealed, and a charcoal canister, mounted underneath the front lefthand wing, collects the petrol vapours generated in the tank when the car is parked.

The canister stores them until they can be cleared from the canister (under the control of the fuel injection/ignition system ECU) via the purge solenoid valve. When the valve is opened, the fuel vapours pass into the inlet tract, to be burned by the engine during normal combustion.

8 To ensure that the engine runs correctly when it is cold and/or idling, the ECU does not open the purge control valve until the engine has warmed up and is under load; the valve solenoid is then modulated on and off, to allow the stored vapour to pass into the inlet tract.

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