Help ID a Disconnected tube 1979sc

[vik000]

Newbie 1979 911sc owner. While working on a heater backdate on the driver side I found this loose tubing. I’m not sure if I unplugged it accidentally or it was like that. It starts from from a port behind the airbox, behind the airbox and around the driver side of the engine, under the heater duct, and was hanging down near the engine tin where the driver side duct passes through to the heat exchanger duct.

Is it a vacuum hose? Is it part of the smog pump system? Afraid to start the car up until I know where this is supposed to go.

Any ideas?

[vik000]

Here is where I trace it to.

[shoooo32]

Vacuum advance to the distributor. '79 only has one and it's not color coded like the later SCs

[kltarga72]

You should see a metal tube on the vacuum diaphram which is attached to the distributor, the hose just slides onto the tube, no clamp needed

[vik000]

This community is great! Thank you so much!

[shoooo32]

I feel bad you have to run that smog pump. Fingers crossed Leno's law passes and you can ditch that junk.

[vik000]

Oh man, I totally agree.

Once it passes (and I think it will in some form), I will ditch the pump, switch to headers, and finally order the AchtungKraft valved exhaust I have been eyeing.

[vik000]

Ok so still don’t have this right.

there is clearly a braided vac line on the one port I see on the side of the distributor. It starts right behind the air box. I believe this is the advance line.



My mystery line starts kind of behind that one. It attaches to a T junction and two other vac lines. I was looking at the diagrams on this site:

https://nineelevenheaven.wordpress.com/vacuum-connections-on-the-k-jetronic-for-the-911-sc/

Could I be looking at an unused cruise control line (green)? I didn’t think my car had cruise control optioned but if it did it was removed by a p.o. Cruise control was not listed on the spec sheet I got from Porsche recently.

[vik000]

Could it be a connection to the smog pump that isn’t on these diagrams?

[vik000]

I think I figured it out.
79sc California car with smog pump still in place
I believe the loose vacuum line was going to the air pump diverter valve here.
Does that seem right?

From my reading on this site, I think can leave this unplugged without consequence.

[mike sampsel]

Originally Posted by vik000

I think I figured it out.
79sc California car with smog pump still in place
I believe the loose vacuum line was going to the air pump diverter valve here.
Does that seem right?

From my reading on this site, I think can leave this unplugged without consequence.

Yup, I use my Line off the dizzy to run my active spot cat. I took my smog pump goodies off in 2019 (mines a '78) and there was a vacuum line to the port you picture.

[vik000]

Awesome. Thanks!
So I just left that disconnected since it is part of the smog pump system.
Car backfired (at least I think that is what happened) the first time I started it (never had that happen before) but then recovered and has been running fine the last two days.

[PeteKz]

Put a plug in the end of the hose too.

[mike sampsel]

Originally Posted by PeteKz

Put a plug in the end of the hose too.

Or plug the nipple on the dizzy, that's easier for me, if you can remember where you put the hose you remove.