Tom:
Way common back in the days of racing VW Sedans (yes, everyone, we used to race them....)
There are two-contact oil pressure sensors from VDO. Some sensors have 1/4" fast-on tabs, others have screw terminals - both work the same. However! They work bass-ackwards for managing a fuel pump, but they're easy to adapt:
One contact goes to a dial pressure gauge and provides variable output, while the other one goes to the Idiot light and is a normally closed switch, meaning that when there is no oil pressure the contacts close.
To use it as an electric fuel pump interrupt, simply install a DPST relay (like a driving light relay) to the sensor contact, and the fuel pump hot lead to the "working" side of the relay such that when the engine is running and there is oil pressure, the relay is "open" (not energized), the relay contacts are closed and the fuel pump is running.
When the engine loses oil pressure (and the light would normally come on) the relay closes, opens the contacts and the fuel pump stops until oil pressure is restored.
Bear in mind that if you have normally low oil pressure when idling (like when your engine is old and worn like me) then you risk having the fuel pump cut out at idle. You also may need an over-ride for starting purposes, for that starting period before oil pressure comes up.
Like I said, easy to adapt, but has some impracticality related to it.
A better solution is to get the mercury bulb switch from a round, Honeywell home thermostat and attach it to something upright in the car such that the mercury blob closes the circuit when the car is upright. Then, wire it into both the ignition and fuel pump circuits such that, when the car overturns, the murcury blob drops away from the contacts and the engine and fuel pump BOTH stop instantly.
Total cost, with relay.......about $25 bucks, new.
Contribution to your peace of mind - priceless.
gn
