The pump contains a 3 port solenoid, a pump that
contains a switch, a spring loaded canister vent valve
seal, 2 check valves and a spring/diaphragm.
OPERATION
Immediately after a cold start, when the engine
temperature is between 40°F and 86°F, the 3 port
solenoid is briefly energized. This initializes the
pump by drawing air into the pump cavity and also
closes the vent seal. During non-test test conditions,
the vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling. This is due to the operation of the 3
port solenoid which prevents the diaphragm assem-
bly from reaching full travel. After the brief initial-
ization period, the solenoid is de-energized, allowing
atmospheric pressure to enter the pump cavity. This
permits the spring to drive the diaphragm which
forces air out of the pump cavity and into the vent
system. When the solenoid is energized and de-ener-
gized, the cycle is repeated creating flow in typical
diaphragm pump fashion. The pump is controlled in
2 modes:
PUMP MODE: The pump is cycled at a fixed rate
to achieve a rapid pressure build in order to shorten
the overall test time.
TEST MODE: The solenoid is energized with a
fixed duration pulse. Subsequent fixed pulses occur
when the diaphragm reaches the switch closure
point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5 inches
of water.
When the pump starts, the cycle rate is quite high.
As the system becomes pressurized, pump rate drops.
If there is no leak, the pump will quit. If there is a
Fig. 1 ORVR System Schematic
1 – FUEL CAP
2 – RECIRCULATION TUBE
3 – LIQUID SEPARATOR
4 – PURGE
5 – W/LDP
6 – BREATHER ELEMENT
7 – W/O LDP
8 – CANISTER
9 – ROLLOVER VALVE
10 – FUEL TANK
11 – CHECK VALVE
12 – CONTROL VALVE
JX
EMISSION CONTROL SYSTEMS
25 - 27
DESCRIPTION AND OPERATION (Continued)