Testarossa 0.0% CO mystery - KE-Jetronic

Hello everyone !
1st time I'm posting here after some extensive readings about Testarossa KE-Jetronic issues...

While trying to adjust the CO on a KE-Jetronic Testarossa, I found that left bank never move from 0.0 % while right bank is hard to bring below 1.0 %.
Left bank exhaust gas are cold while right are hot as it could be expected.

I tried to bloc the inlet of the secondary air injection filter with no success, thinking that additional air could be the cause for 0.0% CO reading.

While I'm going to check again the workshop manual to try to find a clue, I though why not asking the question here as maybe some of you already encountered the isse.

Now, the background of the story :

I came to help a friend with his Testarossa injection when his mechanic told him after a major service that the distributor should be sent for rebuilt as the car wasn't running great.
This guy is a very talented mechanic but K and KE-Jet are not his speciality.
Knowing that I had overhauled the K-Jet of my Porsche 930, this friend asked me to take a look at his car.
The car is very clean French KE-Jet with catalytics (removed) with around 40.000 km.

At 1st the car was running rough but running, I found a leaking EHA on one of the distributor.
1st decision was then to change both EHA for new Bosh units.
It didn't solve the problem and the car was running rougher and rougher.
I noticed that injector seals were very dry not holding the injector in place as well as some tired gaskets between upper and lower part of manifol.
This being known at letting unmetered air going into the system, I changed all those bad looking seals.
This didn't solve the issue as well...
I hooked a test light to the temperature sensor and noticed that there was no power to the electronic part of the KE-Jet system...
I put a jumper instead of the infamous Porsche 928 relay and the car ran great.
That should have been the 1st thing to check but it seems that the relay gave up after I changed the EHA as the car was running better before...
I've also been misleading by the choices of Ferrari to lean the fuel when there is an electronic issue making the car unusable compared to Mercedes where the base setting of the system is design to run properly without the electronics.

So the car is now running great, problem is that previous mechanics tried to adjust the CO screw (enrich) as on a K-Jet to get the car running better.

Now I want to set the CO at factory settings of 0.8 % but as explained before there's something weird going on the left bank.

An idea on what can cause the CO reading to be at 0.0 % on one bank while the other is "normal" ?

 

You're right, I should have introduced myself better.
I joined the forum some time ago when I discovered the epic 308 V12 with Testarossa heads conversion thread.
I also found here some information about DP Motorspor cars as it seems that there are mor owners of DP935 here than on Pelican or Rennlist.
So I'm originally passionate by old Porsche(s), but the appeal of a Ferarri V12 is now real that I had the chance to sit in one...
I do my own mechanic since I'm 14 and as my cars upgarded, my skills and knowledge had to follow so I'm always trying to learn more and understand how each component of my cars operates.

On this particular car, the decat exhaust is not "crossed" so left exhaust for left bank.
The secondary air injection is the "passive" system based on exhaust pulsations, I tried to block the filter inlet with my hand with no difference.

I haven't yet encoutered a thread with the same problem hence my question here, I'm still searching !

 

Thank you !
The answer was obvious but I was fooled by the seemingly good revving engine.
Next I'm going to check for the electric side of fuel supply (not forgetting a quick check that I have spark on both sides).

There might be some electric gizmos that cause sequential failure of components...
The car was pulling strong few weeks ago wen we went took if for a ride before I receive my 4 gas tester to do the final adjustement.

 

Thank you Steve, I remember reading few of your thread about those issues, I'm going to check now.
Something I just remember, the round connector of the relay box below the ECUs were not locking.
It seems that someone pulled on them before braking the locking tabs.
That might be the cause of part of the system not running, I'm going to check the wiring diagram.

 

Went for a quick troubleshooting session tonight :

The connector at the fuse pannel start to have some brownish areas and the contacts are loose inside (lost their elasticity).
AMP 23 pin connector atr the relay bow is loose as well as the locking ring had its tabs broken.
Overheated connectors and locking ring of the AMP connector will be replaced as a peace of mind.

On fuel side, both pumps are running and looking at the HC ppm, it's way higher on the "cold" side so ignition have to be checked.

My 4 gas has a ignition lead clamp for measuring RPM, that shown no ignition on "cold" side

I tryed to swap the coils as a quick check and no difference so back to the wiring diagram to plan my next troubleshooting session focused on ignition...

 

I thought of this exact test, but the analyser went into calibration loop at that moment... and it was time for rosé I should have insisted for one more test
so I'll bring my timing light next time, it should be less quirky than the analyzer...

 

Ran out of Chianti Classico a few month back, yearly trip to Tuscany is coming soon

 

Back to business…
I tried to check for ignition on left bank, nothing came on the timing light before or after the dist.
Had a quick look on the carbon brush in the dist that looked quite worn, pulled it a bit to extend a bit the spring.
Tried to start and no-go… right side lost ignition as well.
Coils and pin 13 of microplex get 12V with ignition on.
Got to think about how to proceed a good step by step diagnosis.
This car doesn’t have the diagnostic plug as shown in the workshop manual, production variations I guess…

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Thanks a lot for the Diagnostic Sheet !

That may motivates me to complete the 25 pin breakout box I started some time ago...

It seems tha this car reached the critical age where things fail while you fix some others...

 

On the drawing for the 412 on the diagnostic sheet, the breakout box is not connected to the Microplex box but I believ it should be connected for complete diagnostic.