Looking at the wiring diagram for the switch on holleys site I am going to guess you have a mis wire. Reason being,

1. you say the pump runs with the key on but stops when the motor is running.

Per their diagram the switch terminal N (normally closed contact) should be wired to the starter relay (start terminal). This puts power to the pump while the engine is being started

Terminal NO (normally open contact) should be wired to the input side of the ballast resistor or to a terminal that is hot in the run position. This puts power to the pump once the engine starts and builds oil pressure

Terminal C is the common and hooked to the pump.

HOLLEY SWITCH INSTRUCTIONS

Depending on how your relay is wired it may also be the problem. (HINT) It may be interesting to note per their digram and instructions, they do not require a relay. (HINT x 2)

A schematic or or drawing of your wiring would help tremendously. keep us posted

I’m not really sure how much of a failsafe the oil switch can be in this particular situation.

The electric pump is feeding a mechanical pump....... so even without oil pressure, and the electric pump turned off...... the motor still runs.

Just eliminate one more item that can cause problems...... the oil pressure switch.

I would just run it off a switched 12v source like most everyone else does.. unless of course there's some mandate for you to connect it through the oil pressure switch. I run the p4070s on a car with a direct 12v, and on a truck just wired into an under hood switched 12v source. Those are very low amp draw pumps and don't even need a relay.

that mandate would be called safety. With a switched 12V the pump will continue to run in an accident potentially pumping gas into a fire. By using the oil pressure switch the pump will not run without the engine running. In the case of an accident that doesn't stop the engine the pump will feed the engine and it will run without pump gas out in the the environment. If it does pump it out into the environment then the engine stops running, no oil pressure, pump shuts off.

But go ahead and do it your way.

Agreed and will mention: say the engine loses oil pressure while running, the switch shuts the pump off, the mechanical ( as already mentioned) will continue to pump and even if the mechanical was not there by the time the fuel bowls are drained the engine most likely will have suffered bearing damage at a minumum.

You don't use the oil pressure switch to save the engine bearings.

It's there so that the electric fuel pump will not continue to pump gasoline if the engine shuts off. Such as in an accident.

If you need something to monitor your oil pressure in order to save your bearings use a gauge or an IDIOT light in parallel.

Okay, I finally figured it out. TJP is correct, I had the NO wired to the NC input and the NC wired to the NO input on the oil pressure switch. I got confused because of the wiring diagram I used to include the relay, which was not from Holley, so my bad. In any event, I really appreciate everyone's input, it helped tremendously. My car is running stronger than it every has, now that I have good fuel pressure at high RPM. I laid down a 1st and 2nd gear burn off this morning that would've have made everyone here very proud!

Thanks again, I really appreciate all the advice! 6T9RR

Damn!