Wiring puzzle on 1974 with a 1977 engine...!!

SorenDK · SorenDK's Garage

Hi guys

Hope for your help here... I recently bought a 1974 with a 1977 2,7 engine (911/81). It apparantly has a stock CIS - it starts and runs. So far so good :-)

It has a permatune installed and regular ignition (point/breaker)

As mentioned the car (and wiring harness) is 1974 - but the engine is a 1977. Unfortunately the PO is an idiot with no idea, so wiring is a mess. And I would like to get this straightened out.

Generally the wiring diagrams are not that easy ... 73-74 is the year they introduced current flow... the 73 diagram does not really fit... and the engine is 1977v

... Coming from a 1969, which is somehow different but yet the same, I could really use some advice in solving this so here goes... hope you like a good puzzle

The red circles are loose wires and/or connectors .. maybe someone knows where these should go?

The green circle is the black/purple - at the moment the tach does not work - i suspect its not connected properly. I remember the black/purple is normally signal to tach... but dont know how it works here...

Could it be the permatune not working - I know the Bosch CDI unit is supposed to whine... but what about permatune?... at the moment its deadsilent. How do I check if its working?

I hope the pictures are sufficient to give you some idea ...

Any help is much appreaciated... maybe one or two of you have the same setup - and experienced the same. At least Im pretty sure some of you guys have had the pleasure of cleaning up the mess from PO's?

THANKS :-)

Photos below...

SorenDK · SorenDK's Garage

SorenDK · SorenDK's Garage

E Sully · E Sully's Garage

There was additional components and wiring added to the '77 cis. Timmy2 Pelican Parts Technical BBS - View Profile: timmy2 Can fabricate and repair harness to work.
'77 had fuel pump wiring safety switch to air flow plate, Aux air valve Aux air regulator Vacuum switch to eliminate hand throttle and aid in cold start.

74-911 · 03-20-2015, 07:13 AM

In the first picture, I have the same connector (3 female connector in the middle of the picture) on my '74 and there has never been anything connected to it. No idea what it was for other than something that was optional ?

timmy2 · timmy2's Garage

I'll take a look in a couple of hours when I am on a PC to really see the photos.
I have done multiple harness conversions for the mid year cars, so I can provide you some instruction.

Jcslocum · 03-20-2015, 07:30 AM

Whatever you do, get those crimp connectors off of the wire loom and properlt solder and heat shrink seal them. That is just a problem waiting to happen.

ThomO · 03-20-2015, 08:44 AM

What he said ^^^^^^^^^

allaircooled · allaircooled's Garage

Quote:

Originally Posted by 74-911

In the first picture, I have the same connector (3 female connector in the middle of the picture) on my '74 and there has never been anything connected to it. No idea what it was for other than something that was optional ?

That is for two stage rear window defogger.

SorenDK · SorenDK's Garage

JC and Thom - you are absolutely right... The wiring will be cleaned... Any idea on the other stray wires?... Suggestions to fix the tach?

Im not sure the perma is working - is there a way to troubleshoot?

Thanks a lot guys... Always a pleasure to seek advice here...:-)

E Sully · E Sully's Garage

If the connector in your first picture has a brown and blue/yellow wire, it is a spare. It's only used on Sportmatic cars.
There are 2 similar connectors. Slightly longer one has red and red/white for the defroster.

timmy2 · timmy2's Garage

To be honest, that looks a real mess.
The Tach signal from the CDI needs to go to the 14 pin connector at the rear of the fuse panel on the '74.
The '77 harness has it going to the white T connector normally by the CDI where the red wire connects to supply switched power to the cdi.
You could run it by piggybacking off the points terminal and running a wire to terminal 9 of the engine harness 14 pin connector
The Brown/Black single wire is for the safety shut off in the fuel pump relay for the '77 FP relay wiring. Not used on the '74.
The white wires to the coil and tach are correct coming from the CDI.
Yellow/Black and Brown wires are for the fan motor for the interior heat on the '77, not used on your '74.
The plug by the light 6 pin plug is a spare grey wire Porsche had on a number of years.
Others are as identified already.
As mentioned, repair the splices.
Kroon on your side of the world, or I could build you a new correct engine and cdi harness.
If you want to do it yourself, the parts are readily available. I would be happy to help you understand the current flow diagrams. Do you have both the '74 and '77 prints?