Pins 12 & 14 each need to be checked for being grounded, i.e. one lead of the ohmmeter on one pin
and the other lead touched to the chassis. Those pins go to the enrichment relay (AEC) & MUST not be
grounded! You should also disconnect the AEC with the engine running and check the the duty cycle.

I had a long alligator clip wire so used the negative battery post.

All pins on the ECU said O.L.

All pins on the connector said O.L. Except 5 And 16 (grounds) Showed .3 and pin 15 (ECU to FV to OXS relay) showed 4.2 ohms

Is the line between ECU plug and FV shorted? Or maybe the line from FV to OXS relay?

That's definitely not infinite resistance (OL = Open Loop) but I'll let the smarter guys speak.

@ Funracer
The resistane of the FV should read 2 - 3 ohms.
The ECU iself does not provide 12v power to the FV. The FV gets its power from the OSx relay. The other (ground) connection on the FV is connected to the ECU where the ECU applies an interrupting/pwm ground signal on that FV connection. Its pulse width length results in the FV's dutycycle.

Btw. your ECU unit comes with the correct Bosch part no. for a '83 vehicle.

So when all ECU "pin lead to ground" checks result ok, then its also worth checking the inner part of the ECU for water marks or similair.

Mine reads 4.2 ohms. What does that indicate?

To refresh everyone’s memory, if it is over 15C (switch open) which for me in Florida is most of the time, if I unplug my O2 sensor FV should go to 50% duty cycle. Mine does not change at all. I have been trying to get my DC to read 45% for a couple of months now.

I purchased a new O2 sensor on eBay from Walker Products part 250-2103. It was listed as the right part for 1983 911. It has the full harness including the rubber grommet and a continuous wire to the plug. Car ran fine with it for a month but if anyone knows this to be a sensor that will not work for me I can reinstall the old one.

Thanks for all your time and responses

Can someone please explain in detail how to check this. I am checking both the O2 plug and pin 2 for .5 VDC? Both with O2 unplugged? I have the fuel pump jumpered should I leave it like that or put the relay back in. Start the engine and check inside the O2 plug for .5VDC? Or can I just go to run?

Sorry for all the questions. I’d love to take a class in automotive electronics.

Well in a few posts before I read from you ...
Which would fully comply to the specs.

So when do you read 2.8 and when 4.2?

No, ... with everything at factory default plugged to the ECU, OX Relay etc, you just pull the o2 Sensor cable/socket from the plug in the rear left engine compartment.

Then you connect the DMM red connection to the contact of that (orange) plug, the other DMM connection to ground.

Start the engine or bridge the fuel pump relay in the fuse box at the front.
Both do provide current to the ECU. With the ECU powered, you read the DMM if it shows 0.5v.

Done. It show .5 VDC

This is why you listen to the guys that have experience.

I was thinking you had to back pin out of the Lambda box connector at #2 and I would have no clue how to do that easily.

Now that it has sunk in what to do, I feel the fool and see you have already performed this test. Ha!

Just for discussion. Another simple test is to check the unplugged O2 sensor side of that connection while the car is running. Let it warm up and it should read between 0.1V to 0.9V. 0.1v indicating lean exhaust. 0.9V indicating rich. You literally can get your idle AF mixture roughly close to 14.7:1 by adjusting the 3mm adjusting screw until it reads 0.5V.

2.8 ohms was from the wire continuity resistance from ECU plug 15 to OXS relay pin 87A as in the Bentley diagram.

The 4.2 ohms was ECU plug 15 to battery negative post for ground. All the other pins to ground showed OL except 5 and 16 which are BRN ground wires.

Was this done? With that done and with the O2 sensor disconnected, the duty cycle should be close to 50%, if not the Lambda ECU is bad.
Again, the Lambda system is extremely simple to diagnose!

I’m done for the day. I will do that test tomorrow afternoon.

Interesting occurrence, at least to me.
Reconnected the O2 and fuel lines etc. Hit the starter engine started fine ran a bit rough but not to bad. Then shut it off intent on doing more tomorrow.

Then looked under the seat and realized I had not plugged in the OXS ECU connector!
Funny I would have thought it would not start or run with that not plugged in but it did.

Plugged it in and restarted. Ran super smooth but I have not heard it run for a few weeks so maybe that is why it sounded so good.

Tomorrow I will do the AEC test as suggested by mysocal911

Thanks again for all the troubleshooting help. All of you be well and stay 6 feet apart!

Later

http://forums.pelicanparts.com/uploa...1591137532.jpg
http://forums.pelicanparts.com/uploa...1591137532.jpg

Looks pretty clean. Nothing burned or separated that I notice.

Bob,
yes with o2 sensor unplugged ... this is a very useful approach to set up the base/initial CO setting and check the sensor. Well almost, cause with this you try to reach the lambda 1 ballpark (swinging between 0.1 and 0.9v) and before cat Lambda 1 on this engine will result between approx. 1.0 and 1.8 CO % vol. (forget about those charts in the www saying lambda 1 or even AFR 14.7:1 equals a 0.0 CO % Vol., even not measured after the cat). Then after re plugging the o2 sensor the duty cycle of the FV should swing around 50%. Just turn the CO adjustemnt screw a bit more CW till you get a swinging about 45% which gives you a noticable plus of enrichment when accelerating.

Nevertheless I dropped that antique design ECU and developed a new ECU device from scratch where only the original Case and its connector/socket exist for a proper plug'n play install. You can set up almost everything and its totally CPU controlled. Even compensating wrong WUR cold pressures are possible. An optimized WOT enrichment is possible via adjustment where wideband sensors are also supported and can even spot and keep a perfect achieved lambda 0.85 when accelerating.
Im using, testing and optimizing it since almost 1 1/2 Years and works nice.
The dutycylce now does not fluctuate with +- 15% anymore but only with small +- 5% and so also a nice smooth non oszillating idle is the result and no more of that "pull" feeling when crusing.

http://andrewcologne.bplaced.net/911/ECU/software.png

And every state of duty cycle, lambda, engine temp, sensor volt, etc can be checked via a LCD display. To that ECU you can even connect a 5bar pressure sensor signal wire (installed between the WUR and the FD) to for permanent control pressure monitoring.
https://vimeo.com/410685925

Way over my head but really cool. Maybe you will market them someday?

Yes, I will sell them on request.

Nice idea. Rough cost, if that's allowed here?

I run the classicRetrofit CDI unit, couple that with the above and you've got a pseudo mapped SC.....fuel and spark.

Hi Sub8,

well, till now no production in series is planned. This is a private handmade prototype and it's tested since about 18 month. It's developed concept and coding routines are done by myself with assistance of an engineer of electrical engineering regarding the electrical assembly.

Further questions regarding costs or purchasing in this state via PM.

The classic Retrofit is a superb solution and Im thinking of purchasing one as well.
But regarding this ECU concept the thought of a "pseudo mapped" injection with still a K-Jet is not possible.

The solution above till now is totally lambda based, means till now no further hall sensors, no further mapping sensors or whatever need to be installed.
For optimal plug'n play compatibility without any further electronical modifications I kept the original wiring and sensor signals. Means the existing throttle switches i.E.
The only further swap which is needed is the little 15c switch on the right chain housing which will be changed to a 120°c sensor, enclosed with the ECU unit.

So the old ECU unit will simply changed with this one where the LCD-display – if connected – can be put into the ash tray for realtime reports while driving. Adjustments via software will be done via USB.

http://andrewcologne.bplaced.net/911/ECU/ecu-sc-911.jpg

The optimal mixture will still be achieved by the frequency valve which is driven by this ECU as before. But as here a CPU is handling the whole job, its possible to optimize many engine running states like a smooth idle, direct and optimal lambda 0.85 enrichment at acceleration or WOT and ... the support of Bosch LSU based wideband sensor controllers on the market like Innovate, PLX, AEM is given. With that it could also be possible to achieve specific mixtures for idling, cruising and accelerating/WOT. I think thats your point.

It will work with the original unheated o2 sensor, the heated o2 sensor from the 3.2 Carrara and as mentioned above with wideband sensors/controllers.


While developing and testing I and two other testing people with the same 930/16 engine figured out many interesting behaviors of the K-Jet of these US SCs.

Surely your Nano processor has enough memory left that you could include a digital ignition system in your present
Lambda controller, right? It's not that difficult, actually less complex than controlling the mixture.

Yes that exactly what I meant! :)

Let the CIS give you lambda 1 and your box allows everything (well almost) that you would want a 3D mappable solution to do without any of the hassle.....

Sorry for thread hijack!

Hi Dave,

thats what I've been thinking about also.
Reading/passing the (TD) trigger signal between the dizzy and the CDI.
But as till now I was totally in that process of coding/testing/coding etc. of the lambda core, this could be a forthcoming option.

Using the Nano, my ignition design for a six cylinder BMW took about 60 lines of C code with Nano's interrupt input sensing
the distributor signal.

With a narrowband sensor you can only hit the lambda 1 ballpark as it only provides you the "spot on Lambda 1 window" signal within 0.1 and 0.9 Volt.
So with this sensor in regular the lambda 0,85, needed for Acceleration, can only be guessed but I found out how much more duty cycle is needed for a proper hit. The "static 65% duty cycle way" often results far off and for shure with a factory initial CO setting of 0.4 - 0.8% Vol. at 50% duty cycle.

Your wanted approach can be achieved with the wideband sensor, but also here for a functional "pseudo mapping" many more signals must be read like the rpm one from the speedometer/CDI, a manifold vacuum sensor signal etc etc. This is possible but makes the unit very user specific addressed, means a typical 911 DIY "make the best of it" user who is very in mechanics electrics etc. ... lets see :-)

I already temporarely used the rpm signal in the ECU for playing a bit with it – i.E. switching the FV off when deaccelerating – the whole SSIs changed into a nice popping beat box animal which sounded like hell – well at least for 911 sound freaks heroes ;)


I think Funracer will forgive us :-)
As its still dealing with Dwell, Duty Cycle, ECU and more

Yes, I follow you .... and could be the next approach :-)

@ Sub8
Here a video where the needed lambda 0.85 spot for accelerating is perfectly hit and kept when using a wideband sensor with this ECU.

https://vimeo.com/409686215

Great effort on your part. You should have no problem designing an ignition system. A simple design without ignition
maps is possible by using an equation to replicate a basic distributor advance curve.

Car running, O2 disconnected, AEC unplugged DC did not go to 50% and did not change at all.

Checked connector outs 12 and 14 got OL on both. No ground.

Out of a bit of frustration I then unplugged the lambda ECU, car almost died, richened the mixture and set mixture by the “lift the air plate 1mm” method. Took it for its first drive in a month and it ran great.

So is my lambda ECU bad? If so what next?

Thanks

1. What is the duty cycle?
2. When running with the ECU connected and the back of the connector cover removed, measure the voltage
at pins 2, 7, 12, 14.

Did this today. It showed .8V, too rich. As I turned the mixture CCW towards lean it went lower .7V and then dropped instantly to .3 MILLIVOLTS! I tried to reduce it to .5V many times but it did this every time. There was no reading between .7V and .3 millivolts. This is a brand new sensor I installed back in February.

I have 2 other O2 sensors that tested good today. I will put one in tomorrow and see if it works better.

Yes, its very difficult as you must hit the CO mixture that precise so it exactly results in the ballpark for a proper Lambda 1 reading, means 0.1-0.9v. Just a 1/16 turn already affects the mixture significantly seen with the eyes of an O2 sensor.

But I guess here your focus should be set on the ECU – just follow what mysocial911 suggested 2 posts before and let us know your readings.

Why are you now worried about the O2 sensor voltage? Focus on getting the DC to 50% without any inputs on pins 2,7,12,14
(pins 7,12,14 must be above 5 volts, pin 2 at about .50V).

Are you sure with 12 and 14, ... as these lead to the Acc. enrichment unit and AFAIK this includes Schmitt Trigger components, so for me this sounds like affecting the PWM signal where no constant voltage is present. Or am I on the wrong way?

Also 7 leads to the "15°C temp"/"35°Throttle" switches which simply lead to ground when cold or accelerating, which would cause a short circuit if voltage would be present on this wire on the side of the ECU.

http://andrewcologne.bplaced.net/911...rcroswitch.jpg

Actual voltage measurements from key inputs pins of various Porsche 911 Lambda ECUs:

0 280 800 055
2 - .53, O2 input
6 - 12, no Lambda effect (NLE)
7 - 12, enriches at ground (EAG)
9 - 5, NLE
11 - 12, EAG
12 - 12, EAG

0 280 800 006
2 - .53, O2 input
6 - 12, NLE
7 - 12, EAG
9 - 5, NLE
12 - 12, EAG

0 280 800 037
2 - .53 O2 input
6 - 12, NLE
7 - 12, EAG
9 - 5, NLE
11 - 12, EAG
12 - 12, EAG

So for the Lambda ECU (055) in this thread with no O2 sensor and pins 7/11/12 open, a 50% DC should result. It's that simple!

... wrong thought, .... deleted.

Because a previous poster had suggested it and it was easy and quick to test as I had limited time yesterday. Given the results I got I am not sure the O2 is outputting correctly. I will change it to a known good one today and then do the pin voltage tests.

I was turning it far less than 1/16. It went from .7 to less than .1 after barely touching it and did so every time I tried to lean it out.

Car running with Lambda ECU plugged in, AEC unplugged, O2 unplugged shows 80% plus minus a 5%
http://forums.pelicanparts.com/uploa...1591640267.jpg

Car running, ECU connected, AEC unplugged:
Pin 2 is .5V
Pin 7 is 13V
Pin 12 is 13V
Pin 14 is less than 1V

With AEC plugged in:
Pin 14 less than 1V

Ringing from the frequency valve pulses can distort DC measurements with some meters, here DC is actually 50%,
but some meters could indicate 83%;

http://forums.pelicanparts.com/uploa...1591653301.JPG

Closeup of ringing;

http://forums.pelicanparts.com/uploa...1591653411.JPG

Proper DC (50%) using a test light;

http://forums.pelicanparts.com/uploa...1591653553.JPG

Therefore, disconnect the FV and use a test light as the FV, alligator clip to +12V and other end to FV connection at pin 15,
and measure the DC.