With all the recent no oil pressure problems I've read about, I am trying to setup a shut down system. I have a MSD ignition 6AL and a 15# "HOB" switch which grounds on a fall of pressure.
One simple way to wire this is to simply connect the white MSD wire to the HOB switch. One problem with this is that on startup you will have no fire until the oil pressure comes up during cranking. I'd like the car to start with a touch of the key. I will have the mini starter which will shorten the time do to the faster cranking. I also could install a monentary push button under the dash (N Open) for use during cranking. When pressure comes up release the button.
My questions:
How long would the cranking be to bring up pressure? If its less than 1.5 seconds, then a simple white wire to the HOB switch is good for me.
The momentary switch works but it would be nice just to turn the key. Does anybody know of a time delay holding relay that could be wired to the start circuit?
I have heard about some alarm systems causing a misfire code on modern computer cars when the car hits a pothole. I believe the relay is jared to the point that is cut ignition momentarly. My worry is that if I use a relay here that a similar misfire condition could happen.
Your thoughs please.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I have run my car with the white MSD wire hooked to a stock oil pressure switch. The only time that it really cranks over any amount of time is on first start-up of the day.

It really does not hurt anything to crank it over until it builds pressure anyway.

Grainger or McMaster-Carr will probably both have some kind of timer you could wire in though.

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Official Cookie and Mater Tormentor.

You could add a NC (normally closed) relay between the white wire and the oil pressure switch. Have the starter wire also trigger this relay.

Thus the circuit will be open when cranking the engine, and you'll be bypassing this safety feature when cranking.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes