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Injectors doesn't inject

  • Ward627
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18 Feb 2020 13:59 #13193 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Injectors doesn't inject was created by Ward627
Hello,
i'm new on this forum.
I have a problem with my '75 mercedes 450 sl.
The injectors doesn't inject.
I’ve used the website as a guide to check my ECU unit.
After this i may assume that my ECU is broken.

- I’ve checked the power between pin 11 and 16, 11 and 24.
These are both 12,25 as u can see in the attachments, so i think these are correct.

- I’ve checked the trigger contacts between 12 and 14, 12 and 14, 12 and 21, 12 and 22, and they all give a good signal. (see attachments)

- I've also checked if there is a signal between pin 12 and pin 25, but also here i measure nothing.

Dispite this all, there is no constant signal on my injector outputs, (see attachments).
Other components like my fuel pump does work perfectly.
Is there something else that i have to check, to be sure my ECU is broken?
If i'm sure it is broken, is there a possibility to just get a ECU from the scrapyard, with the same partnumber?
Thanks in advance!

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18 Feb 2020 15:25 #13195 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

your dwell on trigger contacts seems to not the same on all the contacts. While dwell does not really matter, I would propose to align trigger contacts. And it is much better to measure all 4 trigger contacts at the same time with a 4 channel oscilloscope. Then you can also monitor the 90° between all 4 of them.

Your pocket oscilloscope seems to be on wrong trigger or it cannot handle injection pulses. I cannot see a single good one and I believe it is due to your measuring method.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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18 Feb 2020 15:30 #13196 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Sorry,

read your thread again. If injectors do not inject at all (no vibration / sound) and your MAP sensor is connected electrically to ECU, and if your measured trigger contacts on ECU connector as well as 3,4,5,6 then it is your ECU. You can use any with the right Bosch no. But I doubt you will find one on scrap yard.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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23 Feb 2020 21:38 #13266 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Replied by Ward627 on topic Injectors doesn't inject
I've tried to switch the ECU unit, with a working one, but still the same.
The injectors won't inject, I've placed little cups underneath the injectors, but there is no fuel at none of them all.
Tomorrow i'm going to check all mass connection.
Does anyone has another idea what the cause may be?
Thanks in advance!

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23 Feb 2020 22:13 #13267 by nordfisch Europe Opel Diplomat 2.8 E
Replied by nordfisch on topic Injectors doesn't inject
Hi Ward,
yes, check the mass connection of the injectors, located on the top of the engine.
All injectors are connected to one single point.

In measuring the injector's resistance at the ECU-plug you can check the connectivity, too.

Regards
Norbert
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24 Feb 2020 12:51 #13269 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

as I wrote above: If you measured pin 13,14,21,22 (trigger contacts) at ECU connector and if you also measured pins 3-6 then you know incoming and outgoing contacts. Also measure pin 24 to have +12V to pin 11 . Otherwise injectors wont operate.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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01 Mar 2020 14:03 #13322 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Replied by Ward627 on topic Injectors doesn't inject
Hi,
I'm probably missing something, but on my trigger contacts i measure a 4V pulse signal as in the pictures above. I measure 12,6 between pin 11 - pin 16 and between pin 11 - pin 24 that drops to 11V when starting. My fuel pump is getting power (2sec) when i put the ignition switch on. But, my injector outputs (3-6) aren't getting any signal
When i switch my ECU, i'm getting the same result. Does anyone maybe have another idea?
Kind regards,
Ward

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01 Mar 2020 14:16 #13323 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

your dwell on trigger contacts seems to not the same on all the contacts. While dwell does not really matter, I would propose to align trigger contacts. And it is much better to measure all 4 trigger contacts at the same time with a 4 channel oscilloscope. Then you can also monitor the 90° between all 4 of them.


Viele Schraubergrüße - best regards, Dr-DJet Volker
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01 Mar 2020 14:20 #13324 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

  1. do injectors inject wehn you switch on ignition and push down throttle? They should do so and you should hear it.
  2. Is your electricla connection to MAP sensor okay?

Viele Schraubergrüße - best regards, Dr-DJet Volker
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03 Mar 2020 08:19 - 03 Mar 2020 08:20 #13327 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Replied by Ward627 on topic Injectors doesn't inject
Hello,
Here the signal taken with a 4 channel scope.

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03 Mar 2020 09:27 #13329 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

well you can see that red and blue have much shorter clsoing times than green and yellow. What I can see it is 170° to 190° . That is long and it shows the wear of your trigger contacts. I would readjust or replace them. However they still operate and it looks like they are in 90° shifts. I cannot see the correct sequence but I guess you have not changed that. Red line seems to have a different voltage level than the rest. That cannot be and I guess that is due to oscilloscope tuning.So work to do on your trigger contacts, but I cannot see a reason why that should not make injectors inject.

Please do the following test:

  • Turn ignition key and listen to fuel pump running for 2 seconds
  • Push down throttle pedal and listen whether you hear injectors tick.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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03 Mar 2020 11:15 #13332 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Replied by Ward627 on topic Injectors doesn't inject
Hi Volker,
I've done the test you've explained, and some of the injectors do inject.
When i turn the crankshaft and push the throttle pedal,other injectors inject,
I've added the scope signal of the injectors when i apply the throttle pedal.
As you can see, only two of them do have an injection puls. I will try to readjust the trigger contacts, and check this again.
Thanks in advance!

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03 Mar 2020 17:00 #13335 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

that could be correct. It means that the ECU can generate injection pulses and ground connection is there. Now please remove fuel pump relay and pin 1 on ignition coil and measure pin 3,4,5,6 again whuile cranking the engine. Both tests can operate without a MAP sensor. Then verify that you see 90Ohm / 360 Ohm on MAP sensor from ECU connector (ECU disconnected) and check that there is no ground connection.

Does your car start and immediately stop again?

Viele Schraubergrüße - best regards, Dr-DJet Volker
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09 Mar 2020 23:35 #13391 by Ward627 Americas (USA / CAN) Mercedes-Benz R107 450 SL
Replied by Ward627 on topic Injectors doesn't inject
I've got my injectors injecting.
I think it was a combination of problems.
First there was bad wiring of the MAP-sensor (I didn't measured any resistance at the ECU) and injectors ( some injectors had a interruption in the wiring),
Also there was one injector that was stuck. I've cleaned them all in a ultrasonic cleaner.
After this all, my injectors are injecting again.
Thanks to all, for helping me out!

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10 Mar 2020 10:45 #13392 by Volker Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Replied by Volker on topic Injectors doesn't inject
Hi Ward,

thanks for updating us. And yes wiring harnesses more and more become a problem.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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