D-Jetronic Problem!!!!!

Hi Danny,

I cannot comment on Sun injector tester. Remember it must not apply 12V pulses !

Your holding pressure seems to fade away a bit quickly. But there is no Bosch spec for it. Your fuel pressure is too low. Must be 2.0 to 2.1 Bar on running engine. But that should not create such low CO.

Noted with thanks, I won't apply 12V pulse. Btw, just curious, what are the behavior of the injectors that would cause a low CO? What should I observe (e.g., volume, spraying angle)?

Too little volume and a stream instead a spray would cause low CO.

Hi there. I have some updates to share:
I have installed the ECU repaired and shipped a week before from BOSCH Classics. It is the second time I work on the ECU.
When I test drive happily with my MB 280SEL, it can perfectly start and drive it. After starting 30sec to 1 minute, there is sawing sound (it is not a problem), then after another 1 minute, it could run perfectly.

The problem is, after a few days of joy ride, the car was cranking but not running yesterday. I quickly check the D-Jetronic system of the car, and the result is below:
1) I unplugged 8 injector wiring plug and install 8 LED light to the wiring plug for testing
2)when IGN ON, cylinder 4,8 has light on, while cylinder 3 & 6 has flashed once.
3) when cranking, only cylinder 2&7, 4&8 have flashing light

I started to think it is the ECU fault, but I have high trust to BOSCH's work. May I ask for guidance if there is any other possible fault that I missed here? Thanks a lot!

IGN ON video:
drive.google.com/file/d/1AJfH3j4KEibGgKW...Ep0/view?usp=sharing

Cranking video:
drive.google.com/file/d/1AJYQzLGOoDKMlX8...8Im/view?usp=sharing

Best regards,
Danny

Hi Danny,

if 1&5 and 4&8 are missing pulses, it means that pulse generation on both tracks in ECU work. Following issues are possible:

1. Trigger contact fault - we have measring gauge and replacement cams
2. Wiring harness TC to ECU fault
3. ECU fault
4. Wiring harness ECU to injector fault
5. Grounding fault of injectors

I propose that you measure signals from TC to ECU

Thanks for your prompt reply and guidance as usual! I followed your instruction and replaced 4 trigger cam with correct clearance 0.45~0.50mm, then inspect:
1) unplug the trigger connector and measure pin 12,13,14,21,22 at distributor, which are all normal without short body
2) unplug ecu connector and use multimeter to measure trigger close and open. When cranking, pin 12~13, 12~14, 12~21, 12~14 have close and open (all normal)
3) unplug ecu connector, check connector power and earth. When IGN ON, pin 24~11 has 12v and pin 16~11 has 12v
4) plug back the ecu connector, measure trigger signal at the back of the ecu connector. When cranking, pin 12~13, pin 12~14, pin 12~21, pin 12~22 have flashing LED light, which means trigger has been sending correct signal to ecu
5) measure signal from ecu to injector at the back of the ecu connector. pin 3 (1, 5cyl.)~eath with no flash, pin 4 (4, 8 cyl.)~earth with flash, pin 5 (6, 3 cyl.)~earth with no flash, and pin 6 (7, 2 cyl.)~earth with flash, which means pin3 & 5 have no signal output

Pin12~13 (multimeter)
drive.google.com/file/d/1B0DwMTiGMij_QJf...tSQ/view?usp=sharing
Pin 12~13 (flash light)
drive.google.com/file/d/1AlsJz-1Bw-hRjzq...EF8/view?usp=sharing
Pin3 and pin 5
drive.google.com/file/d/1B2oTbPRAPWbHOx9...rRI/view?usp=sharing
Pin4 and pin 6
drive.google.com/file/d/1B5ZFkbneiyAozmg...ZuF/view?usp=sharing

Appreciate your help again!

Best regards,
Danny