Engine management system - V8 (Evaporative emissions): Description and operation

Input/Output The input value for the relay windings is battery voltage, the input value for the switching contacts comes from fuse 10 in the engine compartment fuse box. The output control of the switching contacts is direct to the fuel pump motor, and the relay windings are controlled by pin number 18 of connector C0635 of the ECM.

At ignition 'on' (position II) the fuel pump relay contacts remain open until the ECM supplies an earth path for the relay windings via pin number 18 of connector C0635 of the ECM. At this point, the relay windings are energised, drawing the relay contacts closed. This allows voltage from fuse 10 in the passenger compartment fuse box to pass directly to the fuel pump.

The fuel pump relay can fail the following ways or supply incorrect signal: l Relay drive open circuit. l Short circuit to vehicle earth. l Short circuit to vehicle supply. l Component failure.

In the event of a fuel pump relay failure any of the following symptoms may be observed: l Engine stalls or will not start. l No fuel pressure at the fuel injectors.

The ECM performs three types of diagnostic test to confirm the fuel pump relay integrity: l Output short circuit to earth l Output short circuit to battery voltage l Output open circuit

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook.

Evaporative emissions

Refer to Emissions section for description of the evaporative emissions system components. EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Evaporative emission control system.

Secondary air injection (NAS only)

Refer to Emissions section for description of the secondary air injection system components. EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Secondary air injection system.

Fuel tank pressure sensor (NAS only)

Refer to Fuel Delivery section for description of the fuel system components. FUEL DELIVERY SYSTEM - V8, DESCRIPTION AND OPERATION, Description.

Refer to Emissions section for description of the fuel tank pressure sensor. EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Evaporative emission control system.