Discovery II
EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-29
Secondary Air Injection (SAI) Vacuum Solenoid Valve
1 Vacuum port to intake manifold
(via vacuum reservoir)
2 SAI vacuum solenoid valve
3 Electrical connector
4 Vacuum port to vacuum operated SAI control
valves
5 Purge valve clip
6 Mounting bracket
The SAI vacuum solenoid valve is located at the rear LH side of the engine and is electrically operated under the
control of the ECM. The SAI vacuum solenoid valve is mounted on a bracket together with the EVAP system purge
valve.
Vacuum to the SAI vacuum solenoid valve is provided from the intake manifold depression via a vacuum reservoir. A
small bore vacuum hose with rubber elbow connections at each end provides the vacuum route between the vacuum
reservoir and SAI vacuum solenoid valve. A further small bore vacuum hose with a larger size elbow connector is
used to connect the SAI vacuum solenoid valve to the SAI control valves on each side of the engine via an
intermediate connection. The SAI vacuum solenoid valve port to the SAI control valves is located at a right angle to
the port to the vacuum reservoir.
The intermediate connection in the vacuum supply line is used to split the vacuum equally between the two SAI control
valves. The vacuum hose intermediate connection is located midpoint in front of the inlet manifold. All vacuum hose
lines are protected by flexible plastic sleeving.
Electrical connection to the SAI vacuum solenoid valve is via a 2–pin connector. A 12V electrical power supply to the
SAI vacuum solenoid valve is provided via the Main relay and Fuse 2 in the engine compartment fusebox. The ground
connection is via the ECM which controls the SAI vacuum solenoid valve operation. Note that the harness
connector to the SAI solenoid valve is grey, and must not be confused with the harness connector to the
EVAP system purge valve which is black.
The ECM switches on the SAI vacuum solenoid valve at the same time as initiating SAI pump operation. When the
SAI vacuum solenoid valve is open, a steady vacuum supply is allowed through to open the two vacuum operated
SAI control valves. When the ECM breaks the earth path to the SAI vacuum solenoid valve, the valve closes and
immediately shuts off the vacuum supply to the two SAI control valves at the same time as the SAI pump operation
is terminated.
M17 0211
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