Where is my Lambda test port wiring?

['78 SC]

I'm looking for the Lambda test port on my track car ('83 chassis with '82 engine). The car was converted to a club racer in 2009 and has no oxygen sensor, but I want to verify the open loop behavior of the Lambda system.

Here's what I'm looking for (thanks va_alfa for the photo):


Here's what I'm seeing:




The three wires held by the orange zip tie are black, brown and white w/ black stripe.
The original car was heavily optioned and had cruise control.

[Bob Kontak]

Steve,

Thanks for taking pictures with a view.

I did just check this the other day. Just to the left (facing front of car from engine bay) of the left rear shock is a plastic sheath that dives down under the car in a space behind that rear shock. It contains two wires. One is the O2 wire feed to the Lambda box and the other is the green test wire that ends up in that three wired connector.

There is a common sheath for 6" or so and then individual sheaths. Both wires are green but sheath is black.

The red wire into the test connector taps into the bottom of the three fuses and snakes through that grommet hole in your pic (#2) from under the fuse/relay tray. The brown wire is ground and is bolted to a speed nut on the tray. If you look just forward (towards front of car) of the set of relays you will see two square holes at the base. About flush with the base of the big relays. The ground speed nut connects to the side of the hole closest to the rear of the car.

I see a small gauge red wire loop in that grommet hole. ??? Maybe? Look deep under there. I never knew I had a test port until reading about it in forums.

['78 SC]

Bob, you nailed it. Here's what was stuffed down in the gap ahead of the left shock tower (oops, photo is upside down).




Here it is unwrapped. Red, green/white stripe and brown wires plus what I assume is a plug or grommet for the oxygen sensor.


This was probably taped up and tucked away when the headers were installed and the oxygen sensor removed.

Thanks, Bob. Your description of the wire routing put me on the right path. I had assumed the test port came out of one of the larger harnesses.

[Bob Kontak]

Originally Posted by '78 SC

Your description of the wire routing put me on the right path. I had assumed the test port came out of one of the larger harnesses.

Sweet. That light brown bakelite thingie is the male end for the O2.

It is supposed to mount under the fuel pump but mine was toast (broken to bits) long ago. I just epox-ied it up so it had some integrity and it lays in the engine tin tray connected to the O2 sensor. Not pretty but functional.

There is no reason to not use the O2 sensor. It saves gas when cruising, when you don't need extra fuel pissing through your injectors.

The car will work fine without and you have all the lambda box bells and whistles the 83 offers, like WOT enrichment that the O2 sensor has no input into.

However, hook up the O2. Without you run more fuel through than you need. psalt summed it up nicely a few days ago. No O2 sensor is like people smoking cigs. Everything works ok but you just don't live as long.

[Bob Kontak]

I see "headers". No O2 bung, right? Put it on your to-do list for the medium term. Get a bung welded in on the driver's side.

Nice to have an approximate analysis of AF ratio using Lambda box and/or O2 sensor output for to to dial it in.

This is vs an exhaust analyzer which is going to be more accurate.

[nycplumber]

Hi,

How is the test conducted please?

Thanks !!

[Bob Kontak]

Originally Posted by nycplumber

Hi,

How is the test conducted please?

Thanks !!

Well, that's a bit of typing. It's "simple" but takes a lot to explain.

Do you have an analog dwell meter?

Do some searched on dwell meter in the 911 tech forum.

['78 SC]

I hear you, Bob. I recently installed a wide band O2 sensor to monitor AFR. I had a bunch of issues to sort through (incorrect vacuum line hookups, ignition green wire, WUR pressures, cracked WUR diaphragm, AAR opening at idle and leaking injector sleeves).

I've read numerous posts by you, psalt and Jim Williams and now I'm ready to tackle Lambda.
Thanks for your contributions here.