3.2 Carrera - Switched 12V in engine bay?

[911TT33]

Hey guys,
I need to tap into a switched 12V positive terminal somewhere in the engine bay, to power an electric turbo oil scavenge pump that draws < 5A.
The fuse panel in the engine bay all have permanent hot 12V connections.
I need a point that turns on when the ignition is on and engine is running.
I’ll also wire in a 20A fuse in series.
Or is there a point I can tap into in the front fuse panel/block?
Or can I tap it from the same switched 12v red wire that connects to my Crane HI6 ignition system?
Any recommendations?

[wazzz]

You could tap at the coil primary (terminal 15). It is a switched 12V. But I read that you have a non stock ignition system, so this may not apply.
Or else, use terminal 4 on the ICV, if you still have it. It is also a switched 12 positive.

[Dpmulvan]

If you have wiring diagrams anywhere on track 15 will give you keyed power.

[Rodsrsr]

I ran mine off the main front fuse panel (power with ign on) to a timed relay which keeps the pump on for a few seconds after engine shut down. This goes to a small light under the dash with an in-line fuse so I can be sure the pump is operational.

[911TT33]

Originally Posted by Rodsrsr

I ran mine off the main front fuse panel (power with ign on) to a timed relay which keeps the pump on for a few seconds after engine shut down. This goes to a small light under the dash with an in-line fuse so I can be sure the pump is operational.

Nice solution! Do you have a wiring diagram you could share?

I like the idea of a light to indicate all is OK with the pump.

I presume the light just confirms there's power still being supplied to the pump, right?

[911TT33]

Ok, so it looks like Fuse #7 (where my multimeter probe is inserted into) is a Switched 12V circuit from the ignition.

[wazzz]

Beware of fuse numbering as it can be confusing. In the front luggage compartment, there are 3 fuse blocks, block number 1 is the 3-fuse block at the far left on your pic.
Block number 2 is a 10-fuse block. It starts at white fuse on your pic, so fuse #7 of this block (as referred by Bentley diagram) is the white one at the far right in your pic.
For information, block number 3 is another 8-fuse block that comes next when going towards front of car.

Here is a clickable and zoomable pic of the fuse diagram for MY85, showing the three blocks.

The very last block downwards is the one in the engine compartment.

[Rodsrsr]

Originally Posted by 911TT33

Nice solution! Do you have a wiring diagram you could share?

I like the idea of a light to indicate all is OK with the pump.

I presume the light just confirms there's power still being supplied to the pump, right?

Yeah, the light just shows the circuit is working and there is power going to the pump. I just went from the fuse panel like in your pic, to the relay, than to the light and the pump. Mounted the light facing down so its not so in your face.

[avenbugt]

Originally Posted by 911TT33

Nice solution! Do you have a wiring diagram you could share?

I like the idea of a light to indicate all is OK with the pump.

I presume the light just confirms there's power still being supplied to the pump, right?

The light indicates that there is 12V coming on the Fuel Pump, but that doesn't mean that "all is OK with the pump",,,

[Rodsrsr]

Originally Posted by avenbugt

The light indicates that there is 12V coming on the Fuel Pump, but that doesn't mean that "all is OK with the pump",,,

Its sole purpose is to serve as a subtle indicator that the pump is receiving power and the in-line fuse is intact. If the pump stops working while the light remains on, the issue clearly lies with the pump itself.

[avenbugt]

Originally Posted by Rodsrsr

Its sole purpose is to serve as a subtle indicator that the pump is receiving power and the in-line fuse is intact. If the pump stops working while the light remains on, the issue clearly lies with the pump itself.

I know, I have such an indicator for 17 years. Just wanted to make clear that it doesn't mean that you can tell the condition of the pump with that lamp.

[911TT33]

Hmmm, Is there some sort of inline fitting that generates a 12v signal when there’s actual oil flowing through?

[911TT33]

Originally Posted by Rodsrsr

Yeah, the light just shows the circuit is working and there is power going to the pump. I just went from the fuse panel like in your pic, to the relay, than to the light and the pump. Mounted the light facing down so its not so in your face.

Hey mate, where did you tap the constant 12v from, for the relay? Did you get that direct from the battery, or did you find a point in the engine bay fuse panel where there’s constant 12v?

I’ve noticed in my engine bay, my electrician got the constant 12v from the engine bay 3X fuse panel for my Crane HI6 CDI ignition box, when it was installed many years ago.

[911TT33]

So, since this is a “Switched 12v” point on the front fuse panel, can I just tap into it from the right hand side screw, and run the wire to the Relay’s PIN#86?

[Rodsrsr]

That's how I did it. Just to clarify, you don't actually need the relay for these pumps. I ran mine for several years without one but eventually got tired of having to leave the ignition on momentarily after engine shut down to prevent the catch can from overfilling.

I guess it all depends on where and how your turbos are mounted. For my application, the car would smoke every time on start up if I didn't run the pump after shut down. Another thing I do during first cold startup is turn the key on for a few seconds and you can hear the pump moving some oil out.

The timed relay really solved most of these issues for me.

[Rodsrsr]

[911TT33]

Originally Posted by Rodsrsr

Awesome! Thanks for this! 👍🏼

Yeah my TT setup uses 993TT heat exchangers, so the turbos are at the side of the motor, quite low.

They’re a little higher than the oil drain port on the crankcase, so I’m thinking I might try gravity drain initially and if it works OK, I won’t need the complexity of an electric scavenge pump. I’ll see how it goes. 🙏🏼

[wazzz]

Constant battery power available on any of the 3 fuses in the engine compartment.

Switched power available from various points in engine compartment, depending on what remains from stock 3.2. Could be coil primary (terminal 15) or terminal 4 on ICV (already mentioned these in a previous post).

For delayed action after turning ignition off, use relay BT-509, not BT-510.

[911TT33]

Originally Posted by wazzz

Constant battery power available on any of the 3 fuses in the engine compartment.

Switched power available from various points in engine compartment, depending on what remains from stock 3.2. Could be coil primary (terminal 15) or terminal 4 on ICV (already mentioned these in a previous post).

For delayed action after turning ignition off, use relay BT-509, not BT-510.

All good. I got all the connection points in the frunk area and ran the switched 12v from the frunk to the electric scavenge pump in the engine bay via a 12v 20A relay. Everything works fine. Once I get the Beuler BT-509 “delay off” relay I’ll swap out my current relay 👍🏼

[wazzz]

Ok good. You still need a constant battery power so that the "delay off" relay can provide power to the pump during the time set once switched power is removed from trigger input. This constant power can be had from the 3-fuse block in the engine compartment.
But I guess you know that. Just double checking.