1990 MITSUBISHI SPYDER check engine

ECO mode light child restraint parking sensors 4WD ignition

Page 394 of 2103

MITSUBISHI SPYDER 1990 Service Repair Manual ENGINE (NON-TURBO)>
LEAK DETECTION PUMP MONITOR
Related diagnosis trouble codes (DTC)
l EVAP leak monitor small leak detected
l
EVAP leak monitor large leak detected
l
EVAP leak

ENGINE (NON-TURBO)>
LEAK DETECTION PUMP MONITOR
Related diagnosis trouble codes (DTC)
l EVAP leak monitor small leak detected
l
EVAP leak monitor large leak detected
l
EVAP leak monitor pinched hose found
Operation
The leak detection assembly incorporates two primar y functions: it must detect a the
system and seal the evaporative system so the leak detection test can be run.. .
The’ primary components within the assembly are: A three port solenoid activates ‘both of the
functions listed above; a pump which contains a swi tch; two check valves and a spring/diaphragm, a’
canister vent valve (CVV) seal which contains a spr ing loaded vent seal valve.
Immediately after a cold start, between predetermin ed temperature thresholds limits, the three 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 conditions the vent seal is held open by the pump diaphragm assembly
which pushes it open at the full travel position. The vent seal will remain closed while the pump is c ycling
due to the reed switch triggering of the three port solenoid that prevents the diaphragm assembly from
reaching full travel. After the brief initializatio n period, the solenoid is de-energized allowing atm ospheric
pressure to enter the pump cavity, thus permitting the spring to drive the diaphragm which forces air
out of the pump cavity and into the vent system. Wh en the solenoid is energized and de-energized,
the cycle is repeated creating flow in typical diaphragm pump fashion. The pump is controlled in 2 mod es:
Pump Mode: The pump is cycled at a fixed rate to achieve a rapid pressure build in order to shorten
the overall test length.
Test Mode: The solenoid is energized with a fixed d uration pulse. Subsequent fixed pulses occur
when the diaphragm reaches the Switch closure point .
The spring in the pump is set so that the system wi ll achieve an equalized pressure of about 7.5”
The cycle rate of pump strokes is quite rapid as the system begins to pump up to this pressure.
As the pressure
the cycle rate starts to drop off. If there is no leak in the system, the pump
would eventually stop pumping at the equalized pres sure. If there is a leak, it will continue to pump
at a rate representative of the flow characteristic of the size of the leak. From this information we can
determine if the leak is larger than the required d etection limit (currently set at
orifice by CARB).
If a leak is revealed during the leak test portion of the test, the test is terminated at the end of the
mode and no further system checks will be performed .
After passing the leak detection phase of the test, system pressure is maintained by turning on the
solenoid until the purge system is activated. Purg e activation in effect creates a leak. The cycle
rate is again interrogated and when it increases du e to the flow through the purge system, the leak
check portion of the diagnostic is complete.
The canister vent valve will unseal the system afte r completion of the test sequence as the pump
diaphragm assembly moves to the full travel positio n.
Evaporative system functionality will be verified b y using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a shi ft in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test i s passed. If not, it is assumed that the purge syst em
is not functioning in some respect. The LDP is agai n turned off and the test is ended.
TSB Revision