intermittent fuel pump start

[kaypie]

Hi folks, newbie here - thanks for the great forum!

Hoping you can point me in the right direction.
My wifes Sirion (Yaris T3 engine) has a strange issue where the fuel pump only switches on intermittently. Initially I thought it was the fuel pump, so I replaced the Denso pump and filter for a new Bosch unit.

After replacement the vehicle started, idled, and did a long test drive without any issues, several test starts afterwards was also fine.
The car stood for a few hours, when trying to start it again the pump wouldn't switch on.

I'm still testing a theory whereby when I pull the EFI fuse for a minute and replace it, it allows the pump to switch on again (some sort of "reset"?)

Is there perhaps another relay or fuse I can check that could be acting up?

As part of the initial troubleshooting I checked the coils, spark, battery, fuses under the hood. I also disconnected the battery while changing the pump.

Hope you can help!

[kaypie]

I've found this diagram for the internal fuse box behind the cubby, I noticed "Fuel Pump Relay" at the bottom left, so I guess it's worth replacing

[kaypie]

Well I've replaced the relay for what its worth, still nothing :/