× Die Bosch D-Jetronic war 1967 die erste Großserien elektronische Einspritzung der Welt. - Bosch's D-Jetronic was the first mass-production electronic fuel injection.

D-Jetronic Problem!!!!!

  • dnadanny1
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12 Nov 2022 05:11 #18642
D-Jetronic Problem!!!!! was created by dnadanny1
Hi there. Hope you all ell. My car is Mercedes Benz V8 3.5 D-Jetronic. The symptoms are as follows:
1) The car is cranking but could not be started
2) 4,8,2,7 cylinder injectors fuel spraying volume is very high when cranking
3) 1,5,6,3 cylinder injectors has no fuel spraying volume when cranking

That's why i did a quick checking:
1) when ignition on, sometimes 4,8 cylinder injectors has a little fuel coming out, sometimes 7,2 cylinder injectors has a little fuel coming out
2) when ignition on,1,5,6,3 cylinder injectors has no fuel coming out

And then i tried to further measure the trigger point:
1) For pin14 - pin12, the close angle is 159, the open angel is 201 
2) For pin21 - pin12, the close angle is 150, the open angel is 210
3) For pin22 - pin12, the close angle is 156, the open angel is 204
4) For pin13 - pin12, the close angle is 150, the open angel is 210

And then i tried to further measure the ECU wire:
1) For pin11 to ground, it is good and normal
2) For pin16 and pin24 to earth, they both have 11.9v when IGN ON 
3) For pin18 to earth, it has 9.6v when cranking

And then i tried to further measure fuel pressure:
1) when cranking, it has 2.0bar 
2) IGN OFF, it has 0.1 bar

And then i tried to further measure the injectors
1) when IGN OFF, for pin3/4/5/6 to earth, they all have s 2.2 ohm
2) when IGN ON, for pin3/4/5/6 to earth, they all have s 7.1 ohm

And then i tried to further measure the temperature sensor:
1) for pin1 to ground, it has 191 ohm when the temperature is 25 degree Celsius

And then i tried to further measure the coolant temperature sensor:
1) for pin23 o ground, it has 2.0k ohm when the temperature is 25 degree Celsius

The questions from me are:
1) what are the causes for the injectors having small or large fuel spraying volume? is it because of the close angle or open angle?
2) The increase of fuel spraying volume is caused by smaller or larger open/ close angle? 

3) Should I use Norberts gauge adjustment tool or angle meter for better measurement of the close/ open angle?

Thanks in advance for your help! Really appreciate any of your comment!

Best regards,
Danny Cho

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12 Nov 2022 11:21 - 12 Nov 2022 11:23 #18643
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi Danny Cho,

you measured a lot. I will try to comment below:
  1. Your trigger points seem to be working and connected to ECU.
  2. Your battery voltage is pretty low. A good battery has 12.6 V and it charged with 14.4 V. 11.5 V is the minimum for our ECU.
  3. I cannot explain the varying injector resistance. Verify cables, ground points and resistance of injectors on connector.
  4. You loose fuel pressure too quickly. Check where you loose that. Fuel pump non.return valve, hoses, injectors, pressure regulator, cold start valve.
  5. Verify temperature sensors with graph in chapter 13
  6. Injector opening time cannot be adjusted by dwell of Trigger points. ECU only triggers on fall of signal, width is not analyzed[/url]
  7. Injector resistance would have an influence on timing.[/url]

Viele Schraubergrüße - best regards, Dr-DJet Volker
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Last edit: 12 Nov 2022 11:23 by Dr-DJet.

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12 Nov 2022 23:38 - 12 Nov 2022 23:38 #18648
Replied by nordfisch on topic D-Jetronic Problem!!!!!
Hi Danny Cho,
I didn't understand one thing in full:
- Do the injectors 4,8,2,7 leak fuel when only ignition is on, the engine not cranking?

If so, you should remove the electrical plugs and test them again to be sure it's not an electrical problem.
If the injectors are still leaking they can't hold the fuel pressure, they have to be cleaned or replaced.

Regards
Norbert
 
Last edit: 12 Nov 2022 23:38 by nordfisch.

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15 Nov 2022 01:42 #18658
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Thanks both of your replies! I have tried to block fuel-return hose to prevent fuel from returning to the fuel tank, but the fuel pressure still drops to zero. I also tried to block the fuel-supply hose, the fuel pressure still drops to zero. Therefore, it means when ignition on, spraying fuel of 4,8 or 7,2 injectors causes the problem. It also means when I remove the electric connector of 4,8,7,2 injector, the fuel pressure can keep at the level of 2.0bar, no matter ignition on or off. 

The issues right now are:
1) When ignition on, 4,8 or 7,2 injectors are getting ecu signal. Is it normal? If not, what are the potential causes?
2) Should I measure at the ecu connector with ecu disconnected or connected, if I want to know the resistance of injectors?

Thanks again for your kind help!

Best regards,
Danny Cho      

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15 Nov 2022 01:49 #18659
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi Danny,

no injectors should not open just by ignition on. That sound like an ECU problem. Your measuring should be with removed ECU in wiring harness connector.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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20 Nov 2022 05:41 #18660
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Thanks for your help! I have learned a lot from this forum. I have followed the instruction in the chapter 13 per your suggestion, but did not find out any issue/ error.

For next step, I think I need to check ECU. May I know how can I confirm the ECU is faulty? If it is faulty, could you introduce reputable mechanics to me for repairing?

For my knowledge, I would like to know if the trigger fiber rubber cam is severe damaged/ worn, will it have the same symptoms/ performance that I am having right now? If not, what would be the symptoms?

The reason why I ask the above question is that the trigger point is always the cause of over-/ under-fuel injection for the my car,which make the car cranking, but not running. Every time I change the trigger point, the car can start running. After reading and learning from your forum, I learnt that it is not necessary to change the trigger point every time. I learnt how to use the adjusting tool by Norbert Fischer, so this time I would like to try adjusting instead of changing the trigger point, but I still could not tell if it is the ECU or the trigger point being faulty.

Thanks a lot~ Have a nice weekend~

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20 Nov 2022 11:15 - 20 Nov 2022 11:16 #18661
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi Danny Cho,

Bosch itself can repair it: www.bosch-repair-service.com/en/engine-c...ronic-0280002004001/ . Technically I could also do it but I am not a service provider and I cannot deal with import, customs, export ...

YOu had measured your trigger points to be all on same level. That is why I do not understand your question. What changes when you remove and reinstall them?

Viele Schraubergrüße - best regards, Dr-DJet Volker
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Last edit: 20 Nov 2022 11:16 by Dr-DJet.

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26 Nov 2022 03:48 #18697
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
After days of checking, I think it is the issue of the trigger point rather than the ECU, which is aligned with your helpful article.

Since I only know "open/close" of the trigger point, when you say "dwell of the trigger point" or "fall of the signal", could you please further explain on what you mean by dwell or fall? Thanks

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26 Nov 2022 09:11 #18698
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
hi Danny Cho,

dwell is the degree that the contact is closed. 360° being one full turn. Same definition as in ignition contact. SO you can use a dwell meter to measure.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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03 Dec 2022 05:01 #18717
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Thanks for your advice and help! I finally changed a new trigger (for 400 euro), and I was so happy that the car can start very quickly. After a few days of driving (~100km mileage), one day when I tried to start the car, the car could not start this time. Therefore, I took out the 8 spark plugs, and i found that 4,8,7,2 spark plugs are wet and full of fuel, but 1,5,3,6 are dry then I dried the spark plugs and put it back, but the car still could not start. I took out the spark plugs again, still 4,8,7,2 spark plugs are wet and full of fuel, but 1,5,3,6 are dry. Therefore, I dried the spark plugs, put them back, and I disconnected the injector electric connector of 4,8,7,2, the car could start this time.

I have a question:
Why the car can start without injector electric connector of 4,8,7,2, but could not start with injector electric connector of 4,8,7,2 on? Either way the 4,8,7,2 cylinder should not work. My hypothesis is that when the injector electric connectors of 4,8,7,2 are on, it stool the electric signal from 1,5,3,6. :)))

What should be the next-step to troubleshoot the issue? Thanks!

Would like to download knowledge from you all experts. Hope you have a great weekend ahead!

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03 Dec 2022 14:01 #18718
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi Danny Cho,

your engine runs with injectors 4,8,7,2 disconnected? Well that is amazing as it runs on only 4 cyls. Disconnect the other four and you are on the path to win a nobel prize for energy saving.

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Oka back to normal: If your engine dies of too much fuel on these 4 cyls, it should be the ECU causing that failure. It is one branch in ECU. And one last remark: If you had read carefully here you would have noticed that there are methods of readjusting or replacing cams on trigger points for much less money than you payed.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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05 Dec 2022 01:54 #18719
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Ohh yess, thanks for your reminder! :) I had purchased 8 cams from child hospital, and I should chase the delivery again haha. We have contacted the BOCH ECU customer center regarding the ECU, and still pending response.

Btw, it is the only issue that I have been working on since I bought this Mercedes Benz. However, I have another BMW E9 with same year and same D-Jetronic system, but it has no such issue. It is so weird....

Wish you Merry Christmas ahead~ Have been learning a lot from you!

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20 Dec 2022 16:42 #18775
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Thank you for your help! Hope you all have a Merry Christmas ahead! Still have no reply from BOCH ECU customer center. I have came across one ECU repairing workshop online, Oldtimer-Steuergeraete (www.oldtimer-steuergeraete.de/index.php/...onic/prices-shipping). I am wondering if anyone here that has experience working with this workshop could share your feedback or comment? Anything I should be aware working with this type of workshop? Thanks!

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20 Dec 2022 17:09 - 20 Dec 2022 17:11 #18776
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi,

you should find a workshop that knows each and every function block and the reference values for testing it. Bosch Classic has them and I have them. Several claim to be able to repair but fail to verify if what they have repaired work in spec or not. So I clearly recommend Bosch Classic to you.

To be on the safe side you should find someone with a 350 Mercedes around you and swap ECUs.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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Last edit: 20 Dec 2022 17:11 by Dr-DJet.

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23 Dec 2022 05:37 #18780
Replied by dnadanny1 on topic D-Jetronic Problem!!!!!
Hi, hope you are well! I agree with you that I should send the ECU to BOSH for repairing, and that would be my top priority. However, there are some website issues happened that I am working closely with the BOSH customer service team to solve it right now.

As for swapping 350 Mercedes ECU, it would be difficult to find one in Hong Kong. According to your articles, it seems that you don't recommend people buying ECU on Ebay. Are there any other ways I could get one?

Btw, below are some checking information regarding all the connectors at the ECU:
1) Pin3 (1,5) with no signal
2) Pin 4 (4,8) with signal
3) Pin 5 (6,3) with no signal
4) Pin 6 (7,2) with signal

Do you think the above information is sufficient enough to tell that it is the issue of ECU, so that I don't need to find one ECU to verify it? or would you recommend other checking processes that I could carry out to further verify the ECU problem? Thanks a lot!

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23 Dec 2022 10:23 #18781
Replied by Dr-DJet on topic D-Jetronic Problem!!!!!
Hi Danny,

what I can tell you is that your symptoms describe that one branch of PWM in ECU is broken. Provided that this was measured on a running engine.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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