ECU / Unit Control / Injector Troubleshooting

[Cyrano]

Hello everyone,

I am currently working on my engine and I am facing some issues with the triggering pins. I may have missed something, but I could not find any information on the forum…

Basically, when I switch-on the system:

• pin 21 is at 7V approximately and I can feel that injectors 2, 4 and 6 open.
• pin 22 is at 0V and at no time the injectors 1, 3 and 5 do not open.
• when I crank the starter, pin 21 voltage decreases slightly to 6V and pin 22 remains at 0V.

I checked all the wirings and the harness. Everything looks ok (good continuity all along the wiring for all the pins). Fuel pump is powered and auxiliary injector opens when the system is switched-on (before starting).

When testing the pin 12, I have a resistance of 7 Ohms against ground. I understood that it should be direct to ground. Not sure if it is related or not. Pins 21 and 22 are showing an infinite resistance against ground (which makes sense).


Based on my understanding of how the D-Jetronic works, I have the feeling that I am facing an issue with my ECU. Can anyone confirm? Should I check something else on my system before sending the ECU for repair or opening it?

Thanks for the help!

Have a great day!


Side note: there are a lot of information on the forum on ECU/Injection, and it is not always easy to find (research by “ECU” or “control unit” provides a significant amount of results). Most of the case study, troubleshooting guides or conceptual data I could find are related to the surrounding equipment, but not to the ECU itself.
It may be good to have all the ECU/injection related topics listed into one single thread. What do you think?
Here below are some links I found helpful (not already listed in the forum published source):
SW-EM Bosch D-Jet Notes
fuel_injection_fault_tracing.pdf

 

[sfdon]

Measure pin 12..... for voltage.

Have you inspected your trigger points? Not your points- your trigger points. The ones hidden inside your distributor on the side.

Have you looked at the schematic?

Very simple but expensive item that when it wears out you will get no signal at either pin 21 or pin 22 or possibly both.
This is the device that tells the computer to fire the injectors based on RPM.

Sounds like trigger points are worn out or distributor is worn.

There is a tool for measuring wear..

 

[bill]

Hello everyone,

I am currently working on my engine and I am facing some issues with the triggering pins. I may have missed something, but I could not find any information on the forum…

Basically, when I switch-on the system:

• pin 21 is at 7V approximately and I can feel that injectors 2, 4 and 6 open.
• pin 22 is at 0V and at no time the injectors 1, 3 and 5 do not open.
• when I crank the starter, pin 21 voltage decreases slightly to 6V and pin 22 remains at 0V.

I checked all the wirings and the harness. Everything looks ok (good continuity all along the wiring for all the pins). Fuel pump is powered and auxiliary injector opens when the system is switched-on (before starting).

When testing the pin 12, I have a resistance of 7 Ohms against ground. I understood that it should be direct to ground. Not sure if it is related or not. Pins 21 and 22 are showing an infinite resistance against ground (which makes sense).


Based on my understanding of how the D-Jetronic works, I have the feeling that I am facing an issue with my ECU. Can anyone confirm? Should I check something else on my system before sending the ECU for repair or opening it?

Thanks for the help!

Have a great day!


Side note: there are a lot of information on the forum on ECU/Injection, and it is not always easy to find (research by “ECU” or “control unit” provides a significant amount of results). Most of the case study, troubleshooting guides or conceptual data I could find are related to the surrounding equipment, but not to the ECU itself.
It may be good to have all the ECU/injection related topics listed into one single thread. What do you think?
Here below are some links I found helpful (not already listed in the forum published source):
SW-EM Bosch D-Jet Notes
fuel_injection_fault_tracing.pdf

If your trigger points are shot, you will need to get in touch with SFDon. Hopefully he has a replacement. Pay attention to him, grasshopper, for all things related to D-Jet. Get friendly with him, he will eventually save your ass.

 

[Cyrano]

Hi Don,

Thanks for your reply. I use a 123 distributor and the pin 12 is not connected.

My understanding is that pins 21 and 22 should have the same voltage inputs from the ECU. Then the distributor alternatively ground one pin or the other. Is it correct ? In original distributor, the ground goes through pin 12.
In 123 distributor, I guess it is grounded directly to the distributor itself.

 

[Cyrano]

Hi guys,

So, I finally made a trial. All the connections worked correctly, and the 21/22 pins was just the open item,. The good news is that the engine started. The bad news is that the engine did not maintain the idle and stopped after a couple of seconds.

After a few trials to work around the engine itself (incorrect grounding, auxiliary valve, etc.) I noticed that exhaust pipes of cylinders 2, 4 and 6 were "cold". That lead me to believe that the triggering of the injector was not working properly.
Working around the ignition (123) did not provide any better results, so I disconnected the trigger point connector to the white/yellow wires of the 123 distributor and mated it to the original distributor (not installed to the engine).
While I started the engine, my father rotated the distributor by hand, and the engine ran much better (not perfect but could maintain during a few second until we switched off the power).

I am suspecting something is wrong on the 123 distributor or the wiring. Anybody has already faced such issue with the 123 distributor (incorrect triggering)? If so, how can I sort this out?

By the way, I'll look for a distributor rotor (12 11 1 355 866) as this is the only missing piece of my original ignition. If anybody has a spare...


Below is a picture of the engine and its bench.

Happy Sunday!

 

[sfdon]

confused-

"and mated it to the original distributor (not installed to the engine)."

"I'll look for a distributor (12 11 1 355 866) as this is the only missing piece "

you have it or not an original distributor?

 

[Cyrano]

Hi Don,

Sorry for the confusion.

Indeed, I do have the original distributor but not the distributor rotor. I cannot use the original distributor/ignition system because I am missing this piece and all the prices I found on the European website were crazy high...
During my last trip to the US, I bought one rotor at Rockauto , which was supposedly compatible, but the part was too short and not touching the contacts of the ignition cap (~2mm too short). So now, I am a bit suspicious to buy a new one...

I have edited my previous message.

Below is what I am calling the distributor rotor. May not be the right word...

 

[TomHom]

Hi Cyrano,
W&N is asking 190€ for one. Each part getting rare becomes extremely expensive.

I may offer you a used, tested one for 40€ plus shipping. Where is your location now?
Thomas

 

[bengal taiga]

If I correctly understand your dilemma, the one thing preventing that pretty engine from running is the lack of a distributor rotor. One of the impediments is the fact that you are limiting yourself to using a rotor that is rev limited. This type of rotor is especially good for engines driven near their recommended red line/speed limit. However, there are alternatives, that would allow your engine to run - without any mechanical safeguard for engine speed, that is, a distributor rotor that is not rev limited. (Even with a rev-limited distributor rotor, it is still possible to cause such an equipped engine to exceed safe engine speeds by simply downshifting at too high road speed.)

You mentioned purchasing a rotor that was too short. Could it be that you purchased a rotor for a carburetor-equipped model, which uses a smaller (different) distributor and distributor cap? You likely should look for a cap and rotor that fit early E3(si), E24 or E12 models. 12111363422??

If you have the original cap for your distributor, it should be fairly easy to determine whether you have a distributor rotor to work with that cap. Something "like" this? Images are for illustration purposes.

Note, there are many distributor rotor variants. Different shapes, sizes, rev-limitations and resistance/impedance.

Although this is somewhat off-topic, I am sure you are aware that rev limiting distributor rotors come in many flavors and rev limiting speeds. https://e9coupe.com/forum/threads/nos-bremi-distributor-rotors-with-limiter.45964/ https://e9coupe.com/forum/threads/what-else-can-i-check-engine-wont-rev-past-5k.17672/page-2

 

[Cyrano]

Hi all,


@Bengal: The rotor I bought from Rockauto is indeed too short, by a couple of mm. I checked again this morning, and the part is sold in the 3.0CSI engine section (STANDARD MOTOR PRODUCTS GB375). This is why it is a bit confusing. I guess that you are right that the one that I bought is adapted for carburetor distribution version. Unless there is a specific cap to buy that will fit the CSI distributor and the CS rotor, I guess that I have a CS rotor to sell.


I bought a secondhand CSI rotor (thanks again TomHom for the help and reactivity!) and the engine started immediately after the installation. Engine ran smoothly (not perfect but good and smooth). Idle was stable and slightly decreased after a few minutes up to the 900/1000 RPM. Auxiliary air valve was playing its role. Accelerations were very smooth.
This was great emotion! Some parts were not used for more than 40 years and they are still running great.


It confirms anyway that there is something wrong with the 123ignition. I am in contact with the support team to identify the issue (I hope there is something I am doing wrong). I’ll keep you all posted.

Have a great day!

 

[Cyrano]

Alright...

So... We tried again to start the engine to tune it, but it refused to run.

Basically, it starts well for a few seconds but does not run. It is like if the 6 main injectors were not triggered.

We checked:

• Fuel pressure: ok - set to 2 bars and maintained when the fuel pump is stopped.
• Air temperature sensor: ok - resistance is within spec.
• Water temperature sensor: ok - resistance is within spec.
• Thermocontact sensor: ok - resistance is within spec.
• Calculator grounding: ok - calculator box to engine resistance = 0
• Distributor contacts: ok - pin 12 alternate direct contact with pins 21 and 22 up to the calculator connector.

I am suspecting that an incorrect signal is sent to the ECU, "blocking" the function on the 6 injectors. Is there anything you would recommend me to check?

Thanks!

 

[TomHom]

Good morning,
so as you said it run on August 24th, not perfect but good and smooth.
What did you touch in between?
The connectors on the AAV (auxiliary air valve)? Often the connector housing got broken allowing the cables to be put back in the wrong way.
The connectors on the D-Jetronic main relay and on the cold-start-relay?
The connection from the starter to the coil, resistor?
Regards

 

[sfdon]

If it starts and runs briefly and then dies, very likely, it is starting off the fuel that is supplied by the cold start injector. That’s an easy test simply disconnect the cold start injector and find out whether it now refuses to start at all..

 

[sfdon]

Another thought for you if it absolutely refuses to run at all, make sure that the plug to the manifold pressure sensor is installed correctly and that the wires are good if the plug is disconnected, the car will not start

 

[sfdon]

As Tom mentioned the bottom connector must be connected correctly not backwards. The two wires in that connector do two separate things they do not complete one circuit.

 

[sfdon]

If you are not getting a signal from the trigger points in the distributor, you will not have fuel injectors working. Have you inspected your trigger points if the blocks are worn down or a wire is disconnected in it, the signal to trigger the Injectors will not occur

 

[Cyrano]

Hi guys!

Thanks a lot for the ideas. Here are some responses

so as you said it run on August 24th, not perfect but good and smooth.
What did you touch in between?

--> Indeed, the engine run smoothly. Not sure if I can attach a video here... The only thing that we touched was the position of the throttle lever stop. it was a very minor adjustment...

The connectors on the AAV (auxiliary air valve)? Often the connector housing got broken allowing the cables to be put back in the wrong way.

--> We did not touch it from the last run. But I will double check it.

The connectors on the D-Jetronic main relay and on the cold-start-relay?

--> They looked ok. Full pump is engaged when system is powered on and cold start injector is engaged and pins 16 and 24 are showing 12V.

The connection from the starter to the coil, resistor?

--> That seemed to be fine as the engine could start. 12V was present on wires 16 and 24 main relay, even after engine stops.

If it starts and runs briefly and then dies, very likely, it is starting off the fuel that is supplied by the cold start injector. That’s an easy test simply disconnect the cold start injector and find out whether it now refuses to start at all.

--> We tried this and indeed, when the connector of the cold start injector is removed, the engine does not start at all,

Another thought for you if it absolutely refuses to run at all, make sure that the plug to the manifold pressure sensor is installed correctly and that the wires are good if the plug is disconnected, the car will not start

--> I have not checked that sensor. I will look at it.

If you are not getting a signal from the trigger points in the distributor, you will not have fuel injectors working. Have you inspected your trigger points if the blocks are worn down or a wire is disconnected in it, the signal to trigger the Injectors will not occur

--> We checked this and we had good continuity alternatively between pin 12 and pins 21/22 up to the calculator connector.

I'll keep you posted.

Thanks again for the help!

 

[sfdon]

Indeed, the engine run smoothly. Not sure if I can attach a video here... The only thing that we touched was the position of the throttle lever stop. it was a very minor adjustment...


That screw should have 1.5 threads showing at the bottom- no more and no less

The idle adjusment screw is at back of the throttle body facing the firewall.

 

[sfdon]

--> We tried this and indeed, when the connector of the cold start injector is removed, the engine does not start at all,


correct- your 6 injectors are not working...

 

[sfdon]

We checked this and we had good continuity alternatively between pin 12 and pins 21/22 up to the calculator connector.

you understand this is a switch? Operated by a cam in the distributor.