backup fuel pumpo

How we can define if we actually have a low pressure so we can start the second fuel pump ?

I did it a couple months ago with a PMU16, I configured the output of the secondary fuel pump to activate if fuel pressure drop below a certain value, but you need to make sure it latches because when the 2nd fuel pump will kick in the fuel pressure will go over that threshold and it will turn off and turn on again and again. I also make sure there was a warning in the ADU so the driver knows it's running on the backup pump. If I recall correctly, I had a delay enabled after the first fuel pump activate to make sure the 2nd fuel pump doesn't activate while the first one is building the initial pressure.

There's other ways to do it, if you monitor the output of the main fuel pump, and it goes in the error state (no current flowing), you can have the 2nd fuel pump kick in, but it won't activate with this setup if the impeller break and the pump keep running but doesn't build pressure.

I don't have the PMU file with me right now, I'm just trying to recall what I did on top of my head!

Hope it helps,

Frank