Just remember a relay is a remote heavy duty switch that can be mounted close to the load (pump) and triggered from a light duty switch (and wires) that's close to the driver. Inside the relay is an electrical coil that becomes magnetically charged when a current is fed through its windings. Feeding battery 12+ volts and earth to terminals 85 and 86, in any order, will cause the coil to charge with magnetism. This pulls the relay internal contacts together forming a circuit that could carry roughly 30amps of current - these contacts are terminals 30 and 87 - again in any order.
This is how I would do a basic wire up with the limited information you've given us. Connect a light gage wire to terminal C from your push button switch to terminal 85 on the relay. Next feed a wire from terminal 86 and to earth - again a light duty wire will suffice. This will now activate the relay on command and you should hear it click on and off as you trigger your push button switch.
Now the feed for the pump itself. Here we use heavy gage wires which must be fused - refer your pump's requirements. But something in the order of 25amps would be close. So connect a fused power supply wire to terminal 30 and the fuel pump + terminal to 87. Make sure you've got a good earth wire and connections for the pump negative side.
Just remember, electric fuel pumps are dangerous in a collision - eg, engine's off, ignition's on, fuel line's ruptured and fuel's pumping onto the hot exhaust. Give me more info. Is this pump used for permanent fuel supply or is it an auxilary fuel pump? I can help you set it up to protect you and your occupants in an accident. Rob.
Last edited by club327; 05-29-2004 at 10:45 PM.