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barrelroll
Samba Member
Joined: March 25, 2012
Posts: 27
Location: Denver, CO
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 Posted: Sat Apr 21, 2018 5:05 pm Post subject: Oil Pressure Switches, Dual Purpose? |
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I'm working on my '76 bug turning class 11 race car. Someone swapped from fuel injected to carbed and wired the fuel pump on when the ignition is on. When the key is on but the motor is dead it's still pumping fuel which could be a bad thing. Eventually the stock fuel injected case will get replaced with a manual fuel pump case but you are allowed to run a backup electric fuel pump per the rules so the car will always have an electric fuel pump.
Any ideas on an oil pressure switch that has both normally closed and normally open terminals? Normally closed for the oil pressure idiot light and normally open for the fuel pump so it won't get voltage till the motor has oil pressure. I'd also like to find a switch that uses something like a weatherpack or other positive locking terminals, we've had bad luck with spade terminals on race cars.
So far I've done some research and found that the factory oil pressure switch activates between 2.2 and 6 pounds and is either 1/8" NPT or M10 tapered pipe thread but an 1/8" sensor fits in. I found this oil pressure switch listing http://www.wellsve.com/showall_ds_oil.php and am leaning towards a PS188 which is 1/8" NPT. Terminal 2 is normally closed and opens at 2-6 PSI grounding through the switch which would work for the dash light. Terminals 3 & 1 is normally open and close at 2-6.5 PSI which would work for the fuel pump. Does this sound like a good switch to kill 2 birds with one stone?
Anyone have any other ideas? Having 2 switches gives me more spots for leaks/ failures. Would you have a switch bypass button to help fill the line after a fuel filter change or when you are fighting issues? The switch is $5 from rock auto and the connector is $13.
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mtnroads
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Joined: December 06, 2006
Posts: 403
Location: Minkler, CA
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| Posted: Sat Apr 21, 2018 5:40 pm Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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if you add a relay with both N/O and N/C posts one switch will do both functions.
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pax
No Good Deed Goes Unpunished.... |
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cdnltded
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Joined: March 13, 2015
Posts: 381
Location: Pincher Creek, Alberta
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| Posted: Sat Apr 21, 2018 6:50 pm Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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| Yes adding a 5 pin relay will do the job. Just have to wire it the right was. And when I did mine i had to make a prime function to prime the car as my ignition switch didn’t not put power to the relay till it was in the run position |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sat Apr 21, 2018 7:10 pm Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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In stead of some setup kludged together do it right right....
http://revolutionelectronics.com/Fuel_Pump.html
Dale
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“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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cdnltded
Samba Member
Joined: March 13, 2015
Posts: 381
Location: Pincher Creek, Alberta
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| Posted: Sat Apr 21, 2018 9:23 pm Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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Damn I wished i seen that like 2 years ago. That’s slick |
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barrelroll
Samba Member
Joined: March 25, 2012
Posts: 27
Location: Denver, CO
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| Posted: Sun Apr 22, 2018 9:58 am Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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The idea is to have the fuel pump shut off when the motor is not running automatically. So in the event of an accident and the motor stalls the fuel pump shuts off.
| cdnltded wrote: |
| Yes adding a 5 pin relay will do the job. Just have to wire it the right was. And when I did mine i had to make a prime function to prime the car as my ignition switch didn’t not put power to the relay till it was in the run position |
Where are you getting the run signal to trigger the relay from? Ignition switch?
That looks nice but doesn't a normally open oil pressure switch and a circuit breaker on the dash basically do the same thing minus the prime function? How do you know when the internal breaker is tripped? It does look like it would be a nice piece for a play car.
I'm not sold on relays on a race car. I've seen too many fail. Over the years I've worked on a lot of desert race cars and there's a big difference between what works on a play car and what holds up to thousands of race miles. The principals I'm trying to use are: Keep it stupid simple, properly sized wire, circuit breakers and no fuses, no relays, no spade terminals, properly rated switches, everything in loom and labeled, and when done a nice wiring diagram in the car for mid race fixes. |
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barrelroll
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Location: Denver, CO
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sun Apr 22, 2018 3:13 pm Post subject: Re: Oil Pressure Switches, Dual Purpose? |
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| barrelroll wrote: |
The idea is to have the fuel pump shut off when the motor is not running automatically. So in the event of an accident and the motor stalls the fuel pump shuts off.
| cdnltded wrote: |
| Yes adding a 5 pin relay will do the job. Just have to wire it the right was. And when I did mine i had to make a prime function to prime the car as my ignition switch didn’t not put power to the relay till it was in the run position |
Where are you getting the run signal to trigger the relay from? Ignition switch?
That looks nice but doesn't a normally open oil pressure switch and a circuit breaker on the dash basically do the same thing minus the prime function? How do you know when the internal breaker is tripped? It does look like it would be a nice piece for a play car.
I'm not sold on relays on a race car. I've seen too many fail. Over the years I've worked on a lot of desert race cars and there's a big difference between what works on a play car and what holds up to thousands of race miles. The principals I'm trying to use are: Keep it stupid simple, properly sized wire, circuit breakers and no fuses, no relays, no spade terminals, properly rated switches, everything in loom and labeled, and when done a nice wiring diagram in the car for mid race fixes. |
And you willing to play with dubious switches on vague belief oil pressure is the key to everything....
IF you believe oil pressure switch is the key to everything, there is oil pressure switches on SUMMIT racing site that does exactly what you want, without use of relays....
One for example...
http://www.summitracing.com/parts/hly-12-810?seid=...5aEALw_wcB
Also consider your fuel pump will not run UNTIL oil pressure comes up unless you have prime push button... Or you have switch override when key is over to 'start' position (but beware of feed back in circuit)......
Might want to look at link below for some other options...
http://lmgtfy.com/?t=i&q=oil+pressure+safety+switches
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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