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,

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]

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      

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.

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~