I got this reply from Dickson.  From the diagram, I think the tank could be used for a diesel engine day-tank, but some assembly would be required.  Ideally, there should be two level switches, one to control the pump and the second to sound an alarm.  It could be done with just one switch if the external lift pump runs continuously however.  I did a search for level switches and couldn’t find a reasonably priced level switch that could be adjusted for a low level alarm.  The link sent below would be usable to control pump operation but could only be used in that mode unless it were mounted lower in the tank.  It may need an external circuit card to buffer and filter the output.  100ma isn’t enough to activate an external pump or alarm and it isn’t safe to drive an external relay with an unbuffered TTL driver.  Some experimentation would be needed.

To do this right, I think the tank would need an additional port for the low-level.  It may be possible to add a manifold to the two existing ports so no tank modification would be required but this sounds expensive to produce. I don’t have time to experiment with this but I thought I might send it out to see if someone else is interested in experimenting.

Rich