I think
@Downey probably knows as much as Mark (
@65swb45) about the Downey fuel cell
This link has a lot of great information about fuel senders and fuel gauges - especially the Rudi and Downey threads.
I don’t know what year FJ40 you’re building , but pay attention to the empty-full ohms values - pre-72 and post-71 use different ohms values - as do aftermarket senders/gauges - and your sender ohms values must match your gauge ohms values.
Centroid is an outstanding company, with great customer service and a great reputation. They even sent me multiple senders, at their own expense.
I wasn’t able to use them, I could never get my oem gauge to work, with their custom senders, using a Pollak 6-port electric switch and tank-specific electric fuel pumps and senders.
I finally gave up... I needed to get everything working for a long trip. I went to a matched-ohms Autometer gauge/sender and run separate, tank-specific fuel gauges.
But, I’m not saying it was Centroid’s fault.. it could have something to do with my configuration... I just ran out of time and have been happy with two gauges.
Edit: I don’t know about diesel, but I’d expect the senders to work with any liquid... just not positive ... Centroidtell you.