2010 4Runner Limited. I am having an intermittent problem. After the the rig sits for a while maybe 3-5 hours it starts to buzz like the sound the fuel pump coming on. This has happened many times. The dealer has not been able to duplicate the problem while in the shop. It sounds like the fuel pump is on... coming from the fuel tank area.
Well after three times to the dealer and many hours on the phone w/ different techs I have the answer to the Buzzing sound. It turns out that the 4Runner does a EVAP System Leak test after 5 hours of being shut down. I took the info they printed out from TIS (Toyota Tech source they use when they get stumped). I will post what it say.
1. Key-Off Monitor
This monitor checks for EVAP (Evaporative Emissions) system leaks and canister pump module malfunctions. This monitor starts 5 hours after the ignition switch is turned off. At least 5 hours are required for the fuel to cool which stabilizes the EVAP pressure, thus making the EVAP system monitor more accurate.
The leak detection pump creates negative pressure (VAC) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the canister pump module purge VSV based on the EVAP pressure.
In other words the "Buzzing", after many hours of being off, is the Leak Detection Pump testing the system.
Well after three times to the dealer and many hours on the phone w/ different techs I have the answer to the Buzzing sound. It turns out that the 4Runner does a EVAP System Leak test after 5 hours of being shut down. I took the info they printed out from TIS (Toyota Tech source they use when they get stumped). I will post what it say.
1. Key-Off Monitor
This monitor checks for EVAP (Evaporative Emissions) system leaks and canister pump module malfunctions. This monitor starts 5 hours after the ignition switch is turned off. At least 5 hours are required for the fuel to cool which stabilizes the EVAP pressure, thus making the EVAP system monitor more accurate.
The leak detection pump creates negative pressure (VAC) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the canister pump module purge VSV based on the EVAP pressure.
In other words the "Buzzing", after many hours of being off, is the Leak Detection Pump testing the system.
