sexypizzaman said:
I know it would be wise but I am not very electrically enclined so I think I am going to go with the easy way out on this one
So if I do wire it through an ignition 12 volt source I am still confused on how the pump prevents overpressuring?? Will it always be running?? In other words how does the regulator stop the the pump from pumping is my question.
First of all, wiring in a relay is super simple. Do it right or it will leave you stranded. Not using a relay because you don't know how to wire it is like not using a postage stamp because you don't know which side to lick. Just ask.
Secondly, the pump will run as long as the switch is on. The regulator's job is to regulate how much pressure makes it past and gets to the carb. If you put a 90 psi pump in the tank and used a regulator to step it down to 5 psi for a carb, it would only deliver 5 psi to the carb. That's how regulators work. Regulators are like bouncers at a busy club. The club is the carburetor, the bouncer is the regulator, and the 500 people waiting in line are the pressure from the pump. It doesn't matter how many people want to get in, the bouncer only lets 200 in at a time. As the people leave the club, the bouncer lets a few more in. Same thing in a car. The pump supplies excess pressure, the regulator only lets 5 psi through. As the carb flows fuel into the engine and leaves a void, the regulator lets more fuel through and keeps the pressure at 5psi. At wide open throttle, the regulator is flowing alot to keep 5 psi, but at idle, it only has to flow a little bit.
For instance, lets say you run the pump while the car is off. The regulator will let enough fuel through to put 5 psi in the line to the carb, then it shuts the door. Now start the engine. As fuel flows out of the carb and the floats open the valve, the regulator notices that the pressure has dropped and it opens the door a bit to keep up with the requirements. The pump keeps pumping, but there is no fuel moving. Its just spinning its wheels.
If you want the truly best way to wire it (in my opinion) do it this way. Test your oil pressure switch for the dummy light.
If it grounds when it has pressure and doesn't ground when it doesn't have pressure, do this: Use a SPST relay. give post 85 switched power through a small (1 amp maybe) fuse. In fact, your fuse block should have a post that says "accy" that is already fused by the fuse to the left of it. Pre wired for you
Wire post 86 to the oil pressure switch. The wires on 85 and 86 can be very small, like 18ga. Then from the battery through a fuse for the rating of the pump to post 30. Then from post 87 to the fuel pump's + side and ground the - side.
If your oil pressure switch grounds when you have no pressure, do this: Use a DPDT relay. The only difference is that you don't use 87 to go to the pump, use 87A to feed the pump. Everything else is the same.
When you wire it this way, the pump will only run when oil pressure is present. This does two things; First, it only makes the pump run when the engine is running, and 2, if you lose oil pressure, you lose fuel and the engine shuts down to save itself. If you don't wire it like that, the pump will run whenever the key is on, deadheading against the regulator. That means the pump will be running, but not moving fuel and it is hard on the pump. If you ever run out of gas, or if you drain the carb for repairs, all you have to do is turn the key on, take the wire off the oil pressure switch and ground it for a couple seconds. That will run the pump to fill the carb.
A relay is just a remote switch. All you are doing is sending power to the pump through a tiny black box. you use a small wire that simply turns on the power when you want it to. As it is, your steering column already has wires that carry relatively large amperages; turn signals, windshield wipers, starter, all of the accessories. Adding a fuel pump (or any other accessory) will be adding how much amperage gets drawn through the wires from the switch. If you add a relay, you're only adding about 1/4 of an amp to that wire and letting the heavy wire from the battery handle the load for the pump. The accessory circuit in the car uses 14 ga wire. Everything that only works when the key is on is designed to draw amperage through that wire. If you add a significant amount of load by just tapping into the accessory circuit, you run the risk of overloading that circuit, causing headaches, melted wires, and in the worst case, a fire. Ask me how I know. I ripped a dashboard out with my bare hands and unloaded a fire extinguisher in a 66 Bonneville for that exact reason.