Wednesday, March 13, 2013

Rethinking My Power/Start Circuit

I was doing some research on putting electronic fuel cutoff switches on each gas tank to be able to control the flow of gas from each.  The original car had two separate electronic Lucas fuel pumps in the trunk which were controlled by a switch in the car.  Put the switch down and you ran the fuel pump on the right side, and the sender unit right fuel tank was used to drive the one fuel gauge in the car.  Put the switch up and the opposite pump would turn on and the gauge would use the sender in the left tank.

When the 350 was put in, the electronic fuel pumps were removed and a mechanical pump on the engine took over. The tanks were T'ed together so that gas was draw out of both.  When the right hand tank started leaking, the prior owner disconnected it and gas was taken from just the left tank.

I like the idea of having separation between the tanks because I think there is potential to drain one tank dry because the only equalization that can happen is through the Tee.  I could put electronic fuel pumps back there again, but I don't see the need because the mechanical pump works well.  So I'm going to put electronic fuel shutoffs back there instead.  The wire is already there so it will be a simple matter of wiring in and adding it to the fuel selector switch in the dash.

Okay, so I just gave you a bunch of background, but that's not what I wanted to focus on.  Instead, I wanted to talk about how I am changing my Power/Start circuit.   What I found while I was researching the fuel shutoff switches was that some people were connecting the switch to the oil pressure light switch on the engine.  The idea is that if the engine stops, but the ignition is left on the shutoff valves will close off the fuel supply.

So why is this relevant?  Well both the On/Off Switch and the Start Switch that I'm using are LED lit.  When you turn on the On/Off Switch, the switch will glow green and the Start Switch will glow red.  I was trying to think of a way to turn off the Start switch LED after the engine has been started, both because it would be annoying to have the red switch lit all the time, and it also indicates that the engine is running.  That is where the Oil Pressure Light switch will come in handy!  All I have to do is wire the ground side of the Start switch LED circuit to an Oil Pressure Light switch, and I have it made!  An added bonus is that, if the oil pressure ever does go low enough for the switch to turn on, the Start Switch will glow, just like an idiot light!

Here is the new diagram:


Note: All Relays and Switches are shown deactivated or normally open.