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Fuel pump continues running 15 minutes after turning car off?

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I may have found what you are hearing. In another post, links to the hybrid docs were posted, most excellent indeed.

 

 

For 2013 MY, a new family of Hybrid Electric Vehicles (HEV) will be introduced. Some of these vehicles will be

able to charge the battery by plugging the vehicle into the grid as well as using an engine –driven generator and
regenerative brakes to charge the battery while driving (Plug in Hybrid Electric Vehicles (PHEV)); others will only
be using an engine –driven generator and regenerative brakes to charge the battery while driving (Hybrid Electric
Vehicles (HEV)). For both types of vehicle, depending on the vehicle drive cycle, there could be very little or no
engine operation during the driving cycle. This poses a challenge as historically, evaporative system leak
diagnostics has relied on engine vacuum to evacuate the fuel tank and perform a large portion of the leak check
and purge flow diagnostics. Additionally, the Engine Off Natural Vacuum (EONV) test that runs after key off relies
on a exhaust system to heat up underbody components and reject heat into the fuel tank. It is the cooling of the
fuel in the tank that generates the vacuum that enables to EONV test to perform the 0.020" leak check. If the
engine does not run, both of the current engine-running and engine –off evap system diagnostics are not feasible.
In spite of this, the OBD-II regulations still require manufacturers to monitor the evaporative system for leaks and to
perform a functional purge flow check. One solution is to add a vacuum pump that can generate vacuum on
demand to facilitate the evaporative system diagnostics. The system that is being used is manufactured by the
Denso Corporation and is called Evaporative Leak Check Module (ELCM

So what you are hearing, could most likely be this system performing its checks.

 

 

During normal operation, the ELCM is vented to atmosphere through the COV. This allows for purging during

engine operation as well as fuel fill. During ELCM leak detection execution, the vacuum pump is turned on. With
the pump on, vacuum is drawn across the reference orifice and the ensuing vacuum level becomes the threshold
for pass/fail criteria. Once the reference is established, it is time to perform the actual leak testing. This is
accomplished by energizing the COV and turning on the vacuum pump. Depending on the volume of the
evaporative system being evacuated, it could take anywhere from 2 to15 minutes for the vacuum level to saturate.
Once saturation vacuum is reached, the vacuum level is compared against the vacuum level when the reference
check was performed. Vacuum levels lower than the reference check are considered to be fails and vacuum levels
above the reference check are considered to be passes..
The ELCM leak detection test runs at key off if entry conditions such as vehicle soak, fuel level, ambient
temperature, BARO, etc. are satisfied. The test sequence begins with a pump warm-up time of 5 minutes followed
by a reference check calculation. Once the reference check is obtained, the pump is turned off which allows the
vacuum to equalize to atmosphere. The changeover valve is then energized and the Evap system is evacuated.
The pump stays on until the vacuum crosses the reference check threshold or the vacuum trace flat-lines above
the reference check threshold.
Heres the link
Edited by acdii

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