What's next to the oil pressure sending unit on the back of a 440 block?

[rynophiliac]

I just bought this 70 cuda and it has some funny wiring from the previous owner I am trying to get sorted out.  There are 2 holes in the back of the 440 block, one is for the oil pressure sending unit, what is the other one for?

It has two wires coming out of it, one is wired into 12v and the other is wired into the switch that controls the aftermarket fuel pump.

[brads70]

From your picture , looks like one is a mecanical oil pressure gauge and the other looks like a oil pressure sending unit that can be used for many purposes. In your case it sounds like it was used to shut off the fuel pump when the oil pressure drops?

[rynophiliac]

This car has two 12v wires going into the same terminal on the switch that turns on/off the fuel pump.  One 12v wire comes from this little thing on the back of the block, and the other 12v wire comes from the solenoid.  So the fuel pump will not shut off if the oil pressure was low because the other hot wire would have still supplied power to the fuel pump?

[brads70]

Hummm electrical is not my strong point, someone should chime in soon?

[Grec]

If this helps... my 69 440 block does indeed have both these holes tapped, but the passenger-side hole is blocked off with a bolt. Driver's side has the stock oil pressure sending unit in place.

If I had to guess, I'd say Chrysler tapped both holes to use for a sending unit depending on application. ie, if it got in the way on certain setups, use the other side.

I think it's safe to say that whatever it is, it isn't factory.

[rynophiliac]

Yea it seems to me that they are both for oil pressures gauges, one is for a mechanical gauge and the other is for an electrical?  Anyway I'm gonna unhook the wires and see what it does.

[Chryco Psycho]

I tend to agree with Brad , it is a pressure switch & if it is connected to the fuel pump should kill it when oil pressure is lost , I have also seen them used as Ign kill

[burdar]

  However an ign. kill would be a better choice.  There is still plenty of fuel in the carb even if the fuel pump shuts off.  You could do a lot of damage waiting for the carb to run dry.

[BadJoey]

I'm thinking the pressure switch is so the pump does not run when the motor is not running . The second wire could have been a after thought .

[joelson6]

uh, trace the wires and see where they go...........

[rynophiliac]

one wire goes to the solenoid (12v supply) the other wire goes to the fuel pump on/off switch

[PlumCraZRT]

I'm thinking the pressure switch is so the pump does not run when the motor is not running . The second wire could have been a after thought .

I think this is in case a fire breaks out, you can kill the engine and stop fuel flow into the engine bay.  It effectively turns your fuel pump into a mechanical pump.