D-Jetronic Problem!!!!!

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

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
 

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      

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~

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

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!

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!

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!

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, 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!

Thanks for your help! To your advice, I have sent my ECU to BOSH for repairing. The good news is the ECU has returned and working nice. Thanks for everyone's input, special thanks to Dr.-DJet! This forum has been useful and informative as always!

However, there is one follow-up question here:

After reinstalling the ECU back to the car, the starting and driving experience is great. However, the idling is poor. I tested the exhaust with gas analysis machine, which shows the CO when idling is very lean (~0.5%). Therefore, I tried to adjust the knob clockwise at the ECU. The CO did rise gradually. However, when the knob reaches the end, the CO stays at 1.4%. According to the workshop manual, the CO range should be 1.5%~2%. I have checked the idle contact at the throttle switch is closed, the intake manifold does not leak, and the fuel pressure is 2 bar, so i assume everything else are good,

Can I seek your advice on how can I raise the CO into the standard CO range? or did I miss anything here?

Thanks everyone again! Have a good day