Porsche Enthusiasts Club Forum

Plugs and wire colours update:

Brown two prong female plug off ECU loom:



Brown
Brown with two white stripes

Red Plug from behind dash - not on ECU loom:





Four Wires:
White with green stripe;
red with green stripe;
red with white stripe;
green with black stripe

Flat single row connector off ECU loom:





Four wires:
black;
yellow with white

opposite end:
white half green;
green with black stripe


Creme plug in engine bay on engine harness near brake booster:





Quite a short length. Two wires:

red with blue stripe;
purple wire

thanks chaps!

The flat connector from the ECU is the tacho signal and oil level warning light drive to the instrument pod, as follows:
(in the diagram the colours are in German, but they do match!)



Did you get the whole S wiring loom? Otherwise you will have to patch these across to the instrument wiring somehow. Will now look for the others...

Right..getting there! The little red connector is the wiring to the instrument pod and that plug was used on the earlier ECU to take the tacho drive up to the instruments, along with the turbo boost gauge if the wiring loom was fitted into a turbo car. So, all you have to do to get it to work is splice the green/black wire from the flat connector to the same colour wire in the red connector. That will get your tacho working. The white/green wire doesn't seem to go anywhere once it gets up to the instruments, so I wouldn't bother with that.

Now, as your instrument pod is an 86..(it is isn't it?) you won't have the necessary additional circuitry to cater for the feed from the oil level sender switch. All this does is put the STOP light on when the oil level is low, so, unless you have also got a set of instruments from a later car you don't need to worry about the white /yellow and the black wires from the ECU plug.

Hope that helps...only one to go now

Regards, Rhett.

The mystery cable near the brake booster is this:



Tank Venting Valve. Now, I am not entirely sure what that is (sometimes the terminology gets a bit screwed up in translation), but I have a hunch. So I will have a look under the bonnet to confirm when I get a chance.

Oh, the little connector on the ECU with brown and brown/white wires - this is a coding option for Australia apparently - so ignore it!

I think that will do for a minute...........

Regards, Rhett.

Woop!

Excellent stuff - thank you Rhett!

Yes mine is an '86 and the sump doesn't have an oil sender in this engine either! I have the lead that JonM helped me figure out but no oil sender. Weird but convenient as it turns out haha.

What a relief - almost there

Just had a good rummage around in the wiring loom around the brake booster and guess what I found...the tank venting valve connector and wire has been taped up (at the factory), so I didn't even know it was there! So, I think this is used for some sort of emissions control 'stuff' probably for the USA. Therefore, I would just wrap some tape around it and forget about it....it's not needed! One more tick in the box.

How are you going to get around the ignition control module wiring issue? Do you have the right part of the loom?

Regards,

Rhett.

Hi Steve, I just saw your blog address and wandered over to your site. Looks like I will be doing some reading later! - but first impressions are very good, your work and attention to detail is really good, carry on good man.

Hope the wiring stuff has helped, if I can be of further assistance do let me know...

Ah yes!!! A redundant plug - a brilliant German rabbit trail. Thanks for checking all these off the list.

I'm so amped for the weekend now I can't tell you!

As for the tacho wire I'm going to try get that female version of the red or flat plug from my OPC. I recall plugs in PET somewhere.

My engine harness is completely original (bar lengthening the AFM wires) and there is no connector for the ignition module. That's the only harness I got.

I've just seen your earlier post at the bottom of page 1 - had missed that! I do recall some extra wires in that loom running down the left side of the engine bay - I actually rerouted mine slightly in an attempt to tidy up the brake booster crows nest of wires & hoses - I'm going to check and see what's there maybe I'll get lucky as it were & find a connector.

If not I'm stumped - I could possibly buy the correct plug from Porsche and then run the wires but to where? The ecu?

Hi Steve, the chances of you finding the correct wires are unfortunately zero, as your car is an 86 and the S didn't come out till 87, so there would have been no need for Porsche to have made one universal wiring loom that fitted both models (I don't think they did that after either?). The ignition module is vitally important but very simple to wire up. All it really needs is a signal from the ECU, +12V, ground and a feed out to the coil. Thinking about it, it doesn't really need to be mounted where it is on stock 944S, and I don't know why the engineers put it where they did - it is a bit exposed. However, it would keep pretty cool there (if it gets operationally hot?) - don't really know. I will check how hot mine runs after a drive out over the weekend.

The wire from the ECU is one of the shielded cable types that they use for sensors, etc. Basically co-ax to shield from electrical interference. So, you would need to ensure any wiring you did to the module matched that - but that is quite easy to achieve. The connector however is a different matter, you probably can't get that new from an OPC. Might have to look around for someone who is breaking an S and see if they could cut the connector off.

I'm looking at the wiring diagrams for both the 8V '86 and the 87-88 16V models and will be able to advise you about the wiring once I have worked it out.

I might have an ignition module spare somewhere - if you need one? - I will have a look, and I could ask at my local Porsche specialist what they might have too.

Regards,

Rhett.

Steve, I have looked into the wiring and have the following recommendations, see illustrations below:

The above shows the existing wiring from the 86 DME to the coil, basically the ignition module (IM) goes inline, as seen below:


Disconnect the cable going to terminal 1 on the coil.
Route a new cable across from the coil terminal 1 to the IM and connect to its terminal 1.
Route a new cable from terminal 4 on the IM across to terminal C32 on the central electric (this is where the coil gets 12V).
Connect a ground cable to terminal 3 on the IM.
Run the coax wire from the DME connector (central core to DME terminal 1, outer braid to term 14).
Connect the coax core to the IM terminal 5. The braid doesn't need to be connected at that end.

That should do it . I checked if the IM got operationally hot and it doesn't seem to as it does have an integral heatsink. However, I wouldn't position it where airflow might get obstructed as it could start to get hot then. But getting it closer to the DME would mean a shorter run of coax.

Hope that helps.

Rhett im still full of questions...

Obviously My 16vS DME and 16v engine harness connector have the T1 coax already wired in and that wire runs to somewhere - I'm thinking the double row connector at the brake booster?

And:

The wire from my existing Coil to T1 86 DME is already running to somewhere - I'm guessing the double row connector also?

So would the two T1 wires not already be connected?

Mmmm scratches head...And wonders.


Also, Wouldn't it be convenient to mount the IM near the coil?

It would be easy to connect earth & bridge the IM & Coil if theyre near one another - I'm thinking of what existing wiring I can reuse.

Does that make sense?

This has me a little mystified...

Hi, from memory I cannot recall where the DME connector T21 is actually located. Probably under the central electric (fuse/relay box)...is this the double headed connector near the brake booster you are thinking of?

Anyway, your thinking is quite right. At the moment you have a co-ax wire going from the DME to that connector (T21 S wiring), and from there it goes into the existing 86 wiring as an ordinary cable straight up to the coil term 1. Now, here's the thing...the 8V DME obviously has the necessary circuitry to drive the coil directly already fitted and so the signal leaving the DME will be a robust signal that would not get degraded by electrical interference in the engine bay. The 16V DME is different, they chose to use an external driver for the coil (the final stage ignition module), this is driven directly by the DME and that signal will definitely be a lower level signal that simply gets amplified by the IM. So, you are right in thinking that there is a connection being made here, but it goes directly to the coil - so you would need to route it to the IM, and it would be open to electrical interference as it is not shielded in any way.

Presently it would not work and might possibly damage the 16V DME output stage if you tried to run it without the IM in-place, as it is not designed to drive the coil directly.

Yes, you could mount the IM near the coil, but the co-ax cable run would then be longer. I would actually mount it on the firewall or top of the inner wing near the central electric/fusebox. That way, you can get away with a very short run of co-ax and easily break into the existing wiring loom to find the drive cable to the coil. The connection to C32 for +12V would also be easy. Does that make sense? If you need any further help please ask..I can put a diagram together if needed.

Regards, Rhett.

The 14pin DME Connector of the diagram is indeed the double row connector at the brake booster!

Tracing the wires back from the coil into the front wiring harness I landed up at the double row connector at the brake booster. The green wire from the coil is very clear to see:



And the heavy gauge wire goes to Terminal 1 as per the 1986 diagram:




From the other end at the DME- I took a look at the wires coming out of the ECU/DME into the engine wiring harness and there are a number of Green ones like this! As I wasn't getting anywhere with those I figured that all but one would land up connected to something on the actual engine. The only wires that don't would end up at the double row connector.

The thing was on first inspection there didn't seem to be a green wire entering the connector:



I suspected that the green wire to T1 and it's black counter part which should be going to T14 were contained within the larger black cable you can see in this pic above.

So I popped off the cover and now in this pic of the wires coming from the DME you can just make out the black wire going to terminal 14 at top left:



…and hidden below everything else is a lighter green heavy gauge wire going to terminal 1:



So, if I understand Rhett… I now need to figure out how to attached the shielded cable I purchased to this connector block - the core to T1 and the outer braid to T14.

Is there a particular way to do that in this kind of setup - I mean separate the outer braid from the coax cable?

Yep, that is exactly what you need to do, but from the look of the connector on the engine bay side, there is not a terminal post (socket) at position 14 (as it was not needed on the '86 wiring). So, you have several ways you can proceed:

1) Find a similar connector from a breaker and salvage a terminal socket to fit.
2) Purchase a terminal socket from an OPC (if available).
3) Remove the wires from the DME from the connector and make an external connection using some other hardware - crimp-on bullet connectors or that sort of thing.

The best way to use coax is to strip back the outer plastic covering an inch or two to expose the braiding. Then, carefully unpick a hole in the braid close to where the outer covering ends and simply pull the central core back through this hole to give you two separate wires. Bend the braid away from the central core and solder a short ordinary wire to this. You can trim the braid to a shorter length if required here. Then put a piece of heatshrink over the solder joint (or electrical tape). Trim the central core covering back a bit to expose the inner wires, twist and solder - you will now have two easy-to connect wires.

If you take your time and go carefully you should end up with a well-prepared cable. As mentioned before, you do not need to connect the braid at the other end. This can be trimed back and heatshrinked, or taped.

Finally got the bits together to make this adapter loom to fit the IM - a couple of pins from OPC are AWOL but I wanted to get this moving



Separated the coax core from the shield and fitted connectors into plug



Then the other wires including the earth cable



Fits all snug



Thanks Rhett almost there now. To the coil!