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Old 04-08-2010, 07:41 PM   #1
Viperguy324
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Default Fuel pump wiring wizardry

It's 130am here and I think this setup should work.

Double pump setup with safety transducer and prime/bypass switch.

Ground will run direct from Batt to pump1 jumped to pump2 and then grounded.

Positive will run like this.

(engine on)BATT to Transducer 5relay switched on/run direct pump1 jumped to pump2.

(engine off)BATT to Transducer 5relay switched closed to bypass/prime switch 4relay direct to pump1.

Does this make sense to you guys?
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Old 04-08-2010, 08:55 PM   #2
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Quote:
Ground will run direct from Batt to pump1 jumped to pump2 and then grounded.
Why not just run a ground to the chassis right where the pumps are?

Linky on the safety transducer? What does it do? Are you going to hardwire the pumps on through a switch or have something that stops the pumps if oil pressure goes away?
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Old 04-09-2010, 04:13 AM   #3
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Originally Posted by MasterKwan View Post
Why not just run a ground to the chassis right where the pumps are?

Linky on the safety transducer? What does it do? Are you going to hardwire the pumps on through a switch or have something that stops the pumps if oil pressure goes away?

With the ground it is just to ensure good amprage.. Have had so many issues with the fuel controller and power... we decided to just give up of that POS.

The saftey Transducer is nothing more then a pressure switch fixed into the fwd upper oil galley plug. low oil pressure... no worky. That will be the normal operation... if it screws up or the relay has an issue I will also wire in the "prime/bypass" double switch allowing for emergancy use.

http://www.longacreracing.com/catalo...d=388&catid=11
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Old 04-09-2010, 08:24 AM   #4
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Gotcha.. Kind of the opposite of the oil pressure switch for the idiot light. I imagine this thing completes the circuit when you have oil pressure. You're not using the stock ECU? I thought Subaru already had an oil pressure based fuel cut-off built in.

It's good you're doing it this way.

How about running the ground for the pumps to the chassis, the ground for the relay through the transducer switch with a momentary contact to ground (in parallel) so, you can prime it and the 12 volts from the battery to the relay to power the pumps. Instead of the momentary contact, you could use a toggle you toggle on then toggle off when the engine starts. If you forget to toggle it off though and wreck, you won't be protected by the transducer.


GND----->transducer----->Relay Gnd
GND----->Toggle switch -->Relay Gnd.


Bat------>Relay------> Pumps
Gnd------------------> Pumps


Then just Bat relay positive to bat wire coming in to power the pumps.

Last edited by MasterKwan; 04-09-2010 at 08:29 AM.
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Old 04-09-2010, 08:41 AM   #5
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Gotcha.. Kind of the opposite of the oil pressure switch for the idiot light. I imagine this thing completes the circuit when you have oil pressure. You're not using the stock ECU? I thought Subaru already had an oil pressure based fuel cut-off built in.

It's good you're doing it this way.

How about running the ground for the pumps to the chassis, the ground for the relay through the transducer switch with a momentary contact to ground (in parallel) so, you can prime it and the 12 volts from the battery to the relay to power the pumps. Instead of the momentary contact, you could use a toggle you toggle on then toggle off when the engine starts. If you forget to toggle it off though and wreck, you won't be protected by the transducer.


GND----->transducer----->Relay Gnd
GND----->Toggle switch -->Relay Gnd.


Bat------>Relay------> Pumps
Gnd------------------> Pumps


Then just Bat relay positive to bat wire coming in to power the pumps.
not sure I follow you... your way would require the relay to switch to operate.. mine stays closed.. ??
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Old 04-09-2010, 09:12 AM   #6
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Well, I assume you want the relay to switch the high current while you just run low current to control the relay. That's typically why you use a relay. My design allows the pumps to come on Either if you have oil pressure OR if you flip the toggle switch. I imagine you flipping the switch to start the car, then flipping it back off after it starts so the transducer keeps the relay energized.

Maybe the problem is you haven't actually detailed what you expect this circuit to accomplish. Does it just provide safety, does it allow you to run both pumps at the same time or is it supposed to run a single pump at a time. I'm assuming both pumps running in parallel.

Say you want individual control of the pumps instead of running them in parallel


Bat------>Switch-------Pump1
Bat------>Switch-------Pump2
Gnd----->Relay---->Pump Grounds (common pump ground for both pumps)


Gnd---->Transducer----->Relay coil Gnd
Gnd---->Prime Switch--->Relay coil Gnd
Bat----->Relay coil positive.


Here's another layout. You have 2 toggle switches for turning the pumps on and off but,
they only can come on IF the relay is energized and supplying GND to both pump. The relay can be energized either when the tranducer sees there's oil pressure or you flip the prime switch. In this case the safety relay is supplying a common ground to both pumps. No ground, the pumps don't run.
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Old 04-09-2010, 09:20 AM   #7
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I didn't think you wanted to run high current through the transducer. That's why I always leave the transducer in the relay circuit. If you don't want to run a relay at all. That means the transducer has to see full current, potentially from both pumps.

Bat----->Switch---->Pump1
Bat----->Switch---->Pump2

Gnd---->Tranducer---->Common pump ground
Gnd---->Prime switch--->Common pump ground.

No relay part. Pump grounds are connected together and run to the transducer. So the pumps share a common ground through the transducer or prime switch. You know the ground wire HAS to be as thick as the positive right? The both carry the same current.
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Old 04-09-2010, 10:47 AM   #8
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humm, I don't think you understand my first post ...

My layout has 1 switch (single pole, 3 position mom,off,on) 2 relays and the transducer.

to start the car you would prime; activating relay one..then release the switch... switching the relay off and allowing the circut to go to relay 2 which would be switch via the transducer.
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Old 04-09-2010, 11:27 AM   #9
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You're right, your circuit was unclear. Your first post says nothing about a 3 position switch.

I wouldn't use two relays. I'd use a single relay for both priming AND for the transducer. If you switch ground with the transducer/prime switch then you can have a common ground for both pumps.

See, you're all about the 12 volt path but, often you can get a more flexible circuit if you play with the ground path too. If you look at most circuits on cars, they're often hooked to a fixed 12 volts and it's the ground that's applied or taken away to activate/deactivate the parts.

There's a million ways to do it. I prefer the way with:

- fewer parts.
- Lower current through the single points of failure.
- A way to bypass the transducer in case it fails but, there's nothing really wrong with the motor.
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Old 04-09-2010, 11:43 AM   #10
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Quote:
Originally Posted by MasterKwan View Post
You're right, your circuit was unclear. Your first post says nothing about a 3 position switch.

I wouldn't use two relays. I'd use a single relay for both priming AND for the transducer. If you switch ground with the transducer/prime switch then you can have a common ground for both pumps.

See, you're all about the 12 volt path but, often you can get a more flexible circuit if you play with the ground path too. If you look at most circuits on cars, they're often hooked to a fixed 12 volts and it's the ground that's applied or taken away to activate/deactivate the parts.

There's a million ways to do it. I prefer the way with:

- fewer parts.
- Lower current through the single points of failure.
- A way to bypass the transducer in case it fails but, there's nothing really wrong with the motor.
Right, that is how my plan is working it. Please explain how you can make this work directly from the batt with only one relay?
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Old 04-09-2010, 11:54 AM   #11
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My lame assed drawing. It' very possible yours is like this. I've just read over your description another couple times and it's just cryptic to me.

Last edited by MasterKwan; 04-09-2010 at 12:05 PM.
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Old 04-09-2010, 06:15 PM   #12
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ha... Ok I will give it another try.

Power wire comes off the killswitch (FIA 3ohm dump), to 20 Amp C/B, then to relay1*, then on to relay2*, ending at bridge to both pumps. What POL you use to trigger the relays does not matter although we will be using POS on switch and NEG on Trans due to location and safety.

* Relay1, 5 pin passive, Controlled by 3 position switch with one output. Momentary up HOT(prime), center cold, locking down HOT(Bypass). Switched, will trigger relay to Passive power -direct power. Neutral in will be passive to Realy2... that means car can still run and start if relay drops off.

* Relay2, 4pin dead type (std), Controlled by Transducer direct. If transducer or relay2 fails.. bypass can be selected. This allows for a fault bypassing circut meaning if one item fails the other will still operate. Redundentcy pays!

Having a second switch is not needed at all ...nor would you ever want to have something that needs to be switched in the case of an "off". Having crashed a couple times.. if you can focus, you tend to pull red only... never toggle switches.

So normal operation nothing is needed. And there are two safetys built in to this setup.

Hope that makes sense..

Last edited by Viperguy324; 04-09-2010 at 06:21 PM.
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Old 04-09-2010, 06:17 PM   #13
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Your drawing skills are good ... if you can understand my writing it may be worth it to redo it. publish your work.

Sticky for the race guys...
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Old 04-09-2010, 07:59 PM   #14
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Your nomenclature is...unusual.

Your explanation leaves alot unsaid. I get the jist of what you're attempting but, the implementation details are fuzzy. Easiest thing is to punch up a schematic. Hell take a picture of it and post it up.

I'm picturing an A/B switch for the pumps that toggles the single pole double-throw relay (I assume that's what you mean by 5 pin). Which in turn activates relays for each pump. You seem to be saying the pressure sensor is bypassable but, it's not clear how that would be wired in.

Hopefully, it's not going to be some overengineered and unreliable German thing...like my M3.
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Old 07-13-2012, 06:06 AM   #15
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*update

We have had this setup in both race cars for over 2 years now and it has worked flawlessly. And was needed in a crash...

Power wire comes off the killswitch (FIA 3ohm dump), to 20 Amp C/B, then to relay1*, then on to relay2*, ending at bridge to both pumps. What POL you use to trigger the relays does not matter although we will be using POS on switch and NEG on Trans due to location and safety.

* Relay1, 5 pin passive, Controlled by 3 position switch with one output. Momentary up HOT(prime), center cold, locking down HOT(Bypass). Switched, will trigger relay to Passive power -direct power. Neutral in will be passive to Realy2... that means car can still run and start if relay drops off.

* Relay2, 4pin dead type (std), Controlled by Transducer direct. If transducer or relay2 fails.. bypass can be selected. This allows for a fault bypassing circut meaning if one item fails the other will still operate. Redundentcy pays!

Having a second switch is not needed at all ...nor would you ever want to have something that needs to be switched in the case of an "off". Having crashed a couple times.. if you can focus, you tend to pull red only... never toggle switches.

Last edited by Viperguy324; 07-13-2012 at 06:13 AM.
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