A competitor recently asked me a question about the safety of electric
fuel pumps in race cars.  The problem was the cars that originally had
a mechanical fuel pump, the new electric pump would run until the fuel
pump switch or master switch was turned off.  This could be a problem
in an accident if the motor is not running, (most people could easily
forget to turn off the pump).  This is also a problem on cars that
originally came with electric pumps and the emission control computer
has been removed.  This problem is easily corrected.  A low pressure
(under 10psi) "normally open" oil pressure switch can be added to the
fuel pump circuit to activate a relay which controls the pump.  With the
engine not running, there is no oil pressure, and the pump doesn't run.
To install this system, the original oil pressure sending unit can be
removed and replaced with a "T" adapter.  The sending unit is screwed
into one port on the "T", with an  oil pressure switch in the other
port. Check with your local auto parts store for a switch to fit your
size port.  Echlin makes Normally Open switches with 2 terminals in
most thread sizes.  To wire the system, run a wire from one terminal
of the switch to the coil of a 12V relay.  The other terminal of the
switch gets connected to ground.  The other side of the relay coil
is connected to a +12 circuit AFTER the master switch, and after the
"ON" position of the ignition switch or a separate fuel pump switch.
This terminal of the relay is also connected to the Common contact of
the relay.  The Normally Open contact of the relay is connected to the +
lead of the fuel pump, and the - of the pump to ground.  Now if the car
is running, the oil pressure switch is closed, which energizes the relay
and this closes the Normally Open relay contacts turning on the pump.
If the engine stops, the oil pressure drops and opens the switch, which
de-energizes the relay, opening the contacts and turning off the pump.
When the master switch or fuel pump switch is turned off, the entire
circuit will loose all power and the pump will stop.

If you have trouble finding the N.O. switches with a thread for your
car, a N.C. oil pressure switch will work. These only have one terminal
(the other contact of the switch is the body and will be grounded).
With this, you will use the N.C. contact of the relay instead of the N.O.
Make sure that the wire to the oil pressure switch is secure and run in
a way that it will not be inadvertently removed, or the pump will run
with the engine off if the main power is on, but will still shut off
with the main power or fuel pump switch since the pump and relay are
connected after these switches.

Safe racing ...