Does the fuel pump on 5th gen turn on and prime for several seconds to build up the pressure, or it doesn't? I have read various opinions on older models of 4runners and Tacomas.

Looking at the electrical diagram, once the EFI relay and C/OPN relay are activated, it should get power even before the car is cranking.

I check mine yesterday and the pressure was 0 with the key in the ON position. I also put the ear next to the fuel tank when the key was in the ON position, and the pump was not running. It runs and build up pressure around 50psi when the engine is running, or cranking.



According to the repair manual (page 2469), you have to use Techstream to check the pressure with the key in the ON position.

The fuel pump does not prime when turning ignition to on. It will not run until you turn the key to the start position, the engine is running, or activated with a scan tool. It is quite audible from inside the cab when activated with a scan tool, with the engine not running.

Probably true for the 4Runner, but for some other Toyotas, such as my RAV4 hybrid, you can hear the fuel pump run for a few seconds when you open the driver's door to get it. Not sure why the difference.

I dont wanna give bad info, but, i recall my 2008 tacoma would ONLY turn the fuel pump on once the MAF detected airflow past it. So you had to be turning the engine over, for air to pass the MAF, before it would energize whatever relay that turns the fuel pump on.