wiring help please

[jk911]

I am rewiring the original CDI unit back on my car and I am puzzled about something. The connections to the distributor ?

I refer to the diagrams below:

Can someone please tell me if the two connections ie Marked A and B on my diagram connect to each other and on the same terminal of the distributor ?

Where does D (of the CDI) and the earth (on connection B of my diagram) connect to ?

I assume that terminal C (of the CDI) plugs into the connector on the distributor am I correct ?

I don't understand how or where (A) and (B) in my diagram connect to the distributor .

PLEASE HELP if you can.

Thanks.
JK911

[jk911]

After searching various posts I have partly answered my question ie I have determined that My marking "B" is a connection to the BODY of the Distributor. This is now clear.

However I am not sure where or how this connection ia situated on the distributor ?

oes anyone have any information/ pictures or diagrams of this distributor body connection ?

[jk911]

Anyone !

[Gunter]

If it is the body of the distributor, then it is ground and could go anywhere, I think? The '75 has points but no condenser? Yes?
Three spade connectors on the CDI one of which is ground? Just keep bumping your question, there are some good wiring technicians on this board. They'll come to the rescue.

[Jim Sims]

JK911, I don't believe you're using the correct wiring diagram. Are the diagram fragments you posted from the '73 wiring diagram? My '76 should be much like your '75 and it only has one wire going to the distributor. I also have the very terrible reproduction of the "1975 on" wiring diagram in the Haynes manual and a big magnifying glass. Here's some information: The wire leaving the "A" terminal of the CDI housing should be white and it goes to the primary side of the coil. The wire leaving the "B" terminal of the CDI unit is red and should go to a two pole (two pin or two wire) connector under the electrical chassis mounted on the driver's side of the engine compartment; on the other side of the connector it splits into two red wires. One of these goes to fuse 22 which is one of the fuses on the "three fuse" block mounted on the electrical chassis on the driver's side of the engine compartment. The other red wire goes into the wiring harness going forward and eventually connects to fuse 11 up in the front trunk (boot). A white wire leaves terminal "C" of the CDI unit and splices into a black and purple wire right after the black and purple wire leaves the two pole connector (this is the same connector the red "B" terminal wire goes to) under the electrical chassis. This red and purple wire is the one that connects onto the male terminal on the side of the distributor. For reference, the black and purple wire continues on from the other side of the 2 pole connector and into the wiring harness going forward and eventually connects to the tachometer on the dash or instrument panel. Two white wires are shown leaving the "D" terminal of the CDI unit; one is shown going to ground (earth) right away and the other connects to the ground side of the primary on the coil. However, within the wiring harness right before the ground side primary coil connection this white wire also has a brown wire spliced onto it; this brown wire goes to a ring lug terminal screwed onto the side of the fan housing for an additional ground. One additional note: the two white wires (one from terminal "A" and one from terminal "D") going to the primary side of the coil go to a molded connector which plugs into the top of the coil. Clear as mud? Good luck, Jim

[Dana_Drury]

If you get stuck JK, I have the factory manuals for your car, including the Wiring diagrams, you are welcome to borrow them. Also, the guy who completely rewired my car - Vass over at J & L Electrics (Bexley) has, I believe, excellent knowledge now in Porsche 911 wiring from that era.

[Early_S_Man]

JK,

In general, all of the cars with 3-pin CDI-units had a braided ground cable that accompanied the distributor and coil wiring to connect the CDI-unit, coil, and distributor body together with a low-impedance common ground that was independent or secondary to normal engine/body/alternator/transaxle grounds!

At the CDI-unit there is a double male spade [1/4" Faston connector] ground connector that is screwed directly to the magnesium CDI housing outside/adjacent to the 3-pin connector. At the distributor there is a large lug that is normally attached to the M8 (13 mm wrench) hold-down nut that secures the distributor body in place after timing adjustments are made. Likewise at the coil ... the ground cable lug connector fastens to one of the hold-down nuts for the coil bracket.

If the above ground cable connections are not present on your car, I suspect criminal abuse of your car's electrical system by a previous owner or mechanic!

[jk911]

You guy's are legends

Thank you.

Ill let you know how I go .

[jk911]

Thanks again

Last night I wired up the new(used) CDI unit, turned the key and "wow" the car started beautifuly so much better than the GT40 conventional coil that was on it. My tachometer no longer floats and the engine actually sounds different.

Even though the engine feels like its running strong it seems a bit rougher/louder. Is it likeley that I would need to adjust the timing, points and or CO mix ??

[Gunter]

That's a given. First you adjust the valves, then you set the point gap, then the timing, and last, the mixture.
Because you are "Down Under", you'll need a left-handed 13mm wrench on the distributor holding nut.

[jk911]

When you say "That's a given" do you mean that the timing would be thrown out by changing to the CDI ignition ?

Is that because the dwell is thrown out ?

[RoninLB]

Originally posted by jk911
Even though the engine feels like its running strong it seems a bit rougher/louder.

if you put your ear to the exhaust closely, so you hear everything inside, you may notice it sounds cleaner