electric fuel pump wiring

[califkid_66]

how do you wire your fuel pump to oil pressure sensor
i have a sensor one pin normally closed when pressure normally open
so as son as pressure builds up power cuts same sensor as for low pressure light in dash
i want to use what i have
i was thinking using relays
don’t want to order other sensors
first picture the sensor lets power when pressure
second picture is with power but cuts with pressure

[jbcollier]

You would need to use a relay with NC contacts.  The relay would be energized when the oil light is on so the NC contacts would be open.  When the light goes out, the relay coil would lose power and the fuel pump would start.  The NO contacts could use feed from the starter to power the pump during cranking.

A better way to simply put an inertia switch in the series with the fuel pump power supply.  Any impacts would cut off the power.  Much simpler wiring, and you have power to the pump when the ignition is on to prime the carbs properly before starting.

[califkid_66]

was just trying to figure out how to make that sensor work it could work but it’s complicated
in the second diagram i use two relays the first one is goes on with ignition on and powers the second one on 30 and 85  then the power is on 87a and since 86 is connected to a sensor that is nc wich means power goes through the power will go to pin 87 so  basically as soon as there’s pressure the power will cut to the relay and when there’s no power the relay it will switch from 87 nothing on pin to 87a wich will let power from 30 go to 87a and power the pump

the reason i want to plug it to the pressure switch is so the pump doesn’t run all the time only when engine is running if fuel line disconnects or leaks engine will stop and pump will to
the inertia is good for impact but not for mecanical failure i think it would be safer to have both
 it’s just i was trying to figure out how to with a bacward signal
pressure no power instead of pressure powersignal

[jbcollier]

Yeah, I use to wire them that way.  I used a three wire oil pressure switch.  One contact is a normal pressure sensor and the other two a NO switch.  Then you just need one relay.