Author Topic: OIl pressure kill switch  (Read 771 times)

Offline retroboy

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OIl pressure kill switch
« on: June 02, 2021, 07:25:06 PM »
Hello
Just a quick question. I want to chuck my oil pressure gauge in the bin. How do I wire a relay to operate in reverse? IE to go ground my Vertex and subsequently shut down the engine if the oil pressure goes away? Can i use a single terminal OE pressure sender in the block and which pins on the relay
Cheers
Tony

Offline THE FRENCHTOWN FLYER

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Re: OIl pressure kill switch
« Reply #1 on: June 03, 2021, 06:02:25 AM »
Yes you can do that. As a matter of fact the NHRA Tech told me my mag kill wire had to be run through a relay so it shuts down when the master shut off is pushed off. I do not have the relay contact diagram in front of me but it should be fairly simple to use the pressure switch to trigger the mag ground when the pressure goes to zero (NC). Be careful that most pressure switches will go to ground at a low pressure, like 7 psi, not zero, so you must decide how low of pressure you want the mag to shut off. You may also need a bypass wire in the starter crank circuit so you can start the engine with no pump pressure buildup. I also have a low oil pressure idiot light in my cars which is useful to alert you that the mag got switched off due to loss of oi pressure, not some other problem. I also should point out that my oil pressure light flickers when I brake from my burnout so you may also need to address that too.  One more hint - Ford makes a two terminal oil pressure switch (on their modular V8 engines) - that has one terminal NC and the other terminal NO. You may fine that typw of switch useful.

Offline msundstrom

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Re: OIl pressure kill switch
« Reply #2 on: June 03, 2021, 06:54:05 AM »
Terminal placement would be (if using a Bosch style relay) your mag kill wire goes to pin 30 of the relay, pin 87 goes to ground. Pin 85 to fused Battery +, and 86 goes to your oil pressure switch with a switch between pin 86 and the Oil pressure switch so you can open it to start the engine. They do make adjustable OP switches. Moroso, Longacre and some of the NOS companies. Engine may kill when you pull the Parachute at the end, may or may not be an issue. I use a standard Bosch relay for my mag kill and never had any issues as far as mag kill arcing across the relay switch contacts. Spud would be the one to answer that.

Offline retroboy

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Re: OIl pressure kill switch
« Reply #3 on: June 04, 2021, 05:02:34 AM »
Cheers guys

Offline 32bantam

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Re: OIl pressure kill switch
« Reply #4 on: June 06, 2021, 07:09:41 AM »
If you use a standard relay the kill wire may come on and off as oil pressure goes up and down right at the pressure setting. Like turning the key on and off while engine is running!!! You should look into a latching relay. Stays off until 12v+ power goes away.
Steve Walczak

Offline Davidshorm

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« Reply #5 on: August 02, 2021, 05:09:22 PM »
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