Low oil pressure cut-off switch

gnxtc2

Well-Known Member
Staff member
Joined
May 28, 2001
Since running an external belt driven oil pump, I want to install a low oil pressure cut-off switch. I'm afraid that the oil pump belt breaking during a run and destroying a motor if not caught quick enough.

I was thinking about cutting the negative wire to the coil. Would this have any detrement to the motor? Anyone know the amperage of a coil? I was thought about killing the fuel pump but that might cause a lean condition.

Anyone ever install one of these switches? Also another good point is when you first fire the motor, it won't start until the is oil pressure.

http://store.summitracing.com/egnsearch.asp?N=700+115+-122045&D=-122045

or

http://store.summitracing.com/partd...part=SUM-G1438&N=700+-151266+115&autoview=sku

Thanks

Billy T.
gnxtc2@aol.com
 
Never done it but sounds like a good idea. I had a needle bearing out of a rocker get in my external pump during eliminations at BG last year. Locked up the pump causing it to toss the belt - cost me an engine AND a turbo before I realized what had happend.

You could use the switch to cut the power to the injector harness. If you use a relayed master power disconnect, you could wire the switch to kill all the power. FWIW
 
I have to agree with Will on killing the fuel vs spark because I wouldn't want all the unburnt fuel gettin in the cylinders.
 
Never done it but sounds like a good idea. I had a needle bearing out of a rocker get in my external pump during eliminations at BG last year. Locked up the pump causing it to toss the belt - cost me an engine AND a turbo before I realized what had happend.

You could use the switch to cut the power to the injector harness. If you use a relayed master power disconnect, you could wire the switch to kill all the power. FWIW

WOW :eek: :eek: :eek:

Then you are going to need a bypass switch to be able to crank the car. The switch is open when there is the mininum oil pressure. Once the switch detects the pressure is above the mininum, the switch closes and completes the circuit.

Billy T.
gnxtc2@aol.com
 
I wonder if you can kill the orange wire to the XFI unit? I don't know if would cause any damage. Disconnecting the orange wire, you loose fuel pump and ignition power.

Billy T.
gnxtc2@aol.com
 
low oil pressure switch

Hey Billy T,

Give Gary Harmon a call. He installed on on his car. He will be able to tell you exactly what to do. See you in BG.
 
Since running an external belt driven oil pump, I want to install a low oil pressure cut-off switch. I'm afraid that the oil pump belt breaking during a run and destroying a motor if not caught quick enough.

I was thinking about cutting the negative wire to the coil. Would this have any detrement to the motor? Anyone know the amperage of a coil? I was thought about killing the fuel pump but that might cause a lean condition.

Anyone ever install one of these switches? Also another good point is when you first fire the motor, it won't start until the is oil pressure.

Fuel Pressure Safety Switches - summitracing.com

or

Summit SUM-G1438 - Summit® Oil Pressure Safety Switch

Thanks

Billy T.
gnxtc2@aol.com

Oh man, I am in the same boat, I never thought about that issue. Please let me know you come up with. I will do some digging too!!!


Prasad
 
Interesting thread......

IMHO... killing the spark would be much preferred over the fuel...... I would hate to lean it out to kill it. IMHO... hydo-lock in the cylinders is probably not that great of a chance.... unless the valves stay closed.

You could always set up a momentary push buton to "by-pass" the oil pressure switch to get the car cranked.... then the oil pressure switch would take over.....keeping the contacts closed powering the injector harness relay.
 
Or the best thing would be to shut down the ECU that way no cylinder washdown or no lean out during cut off. Pry could be done with a relay.
 
Or the best thing would be to shut down the ECU that way no cylinder washdown or no lean out during cut off. Pry could be done with a relay.

Yes..... could be done to cut off both fuel and spark..... personally I would want the ECU to stay live...... cause you would likely loose your data....if you killed the ECU.

At any rate... you could kill spark and fuel...... but if you were only going to kill one.... kill the spark IMHO....
 
I think I'd cut the ECU. Shut down everything. To hell with the data. You can get that later after you fix the oiling problem.
 
After talking with this tuner expert from Florida, that goes by the name Cal Hartline, he said not to cut the orange wire but cut the pink wire (ignition power to the XFI box).

Billy T.
gnxtc2@aol.com
 
I don't like the idea of putting a relay in the ignition system - potential problem area from many angles. I agree with not killing the pump as it will cause a lean conditon. Killing the injector power seems to be the lesser of all the evils here. It will cause a slight lean condition before the engine kills but nothing like shutting down the pump. You would need to have a bypass to start but that can be accomplished with some double pole relays and a little creative wiring. Not trying to contradict that dude from Florida, but killing power to the ECM even thru the pink wire is essentially doing the same thing only it's going to kill EVERYTHING including data.
 
I'm not so sure I would care about the data if my oil pump drive belt was off. I agree that the key on power feed would be a good choice.
 
I'm not so sure I would care about the data if my oil pump drive belt was off. I agree that the key on power feed would be a good choice.

I too wouldn't worry about data this was brought up I think on how to minimize the damage from a oil pressure loss and I agree with Cal to cut power from the ECU ignition switch feed. And once you get oil pressure while cranking the ecu powers up and car fires up.

Steve
 
Well I installed the low oil pressure cut off switch. I used a NOS fuel cut off switch. NOS part # 15680NOS, adjustable 14-24psi. I have it set around 20lbs. The switch is a re-packaged Hobbs switch. More can be found here: Fuel Pressure Safety Switches - summitracing.com

I cut the B17 (switched ignition) lead on the XFI unit. I also tapped into the load side of the brake switch incase I want to over ride the switch ie: hot start.

I tested the switch and it shuts the car off as if you are turning off the key.

I want to give thanks to Cal for the assistance.

Billy T.
gnxtc2@aol.com

P5010117-1.jpg
 
I'm thinking about doing this as well after last year's catastrophy. Do you have to bypass it somehow to start it until the pump comes on line?
 
....snip....I also tapped into the load side of the brake switch incase I want to over ride the switch ie: hot start.

I tested the switch and it shuts the car off as if you are turning off the key.

I want to give thanks to Cal for the assistance.

Billy T.

That appears to be a good idea...... but...... what if you are balls out down track... and the oil pressure drops right at the end of the run.... and your safety circuit catches it... kills power to the ignition..... but 1/2 second later... you are on the brakes hard.... therefore re-enabling the the ignition..... and the car might continue to run.... Is this possible?
 
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