Mercedes Actros injector bank 1 return fault!!

**shanektm450** · 27th June, 2014, 07:00 AM

Hi to all I have a fault with MR for actros V8 bank 1 return fault cylinder 8,7,3 .
The ECU came to me dead repaired unit truck starts but misfiring on cylinder 8,7,3 the 40n06 drivers are all ok can someone point me in correct direction or give me pin data to power up on bench so I can test to see if both sides of banks get power
Thanks
Shane

ECU A542 447 04 40 001

**megapioz** · 4th February, 2016, 01:10 AM

Hi,
I have more or less the same problem. My fault is MR5626/5726 (valve not impact on cylinders 7 and 8). 40N06 and 25N06 are good and I'm trying to find the buggy part.
I'msure it is an ECU problem cause using a new one engine runs good.

Have you found a solution? Can you share it please?

Greets, Lorenzo

**overs0ull** · 5th February, 2016, 04:56 PM

If connections and cables are checked the
The problem is in the ecu 100% if is temic 1000% .
I have lot experience with kind of problem with mercedes trucks with this ecus every time some chenals comunication missing or no votage to the ijectors.
We can repair it but is depend of the ecu damage.
If need more info pm me

**megapioz** · 7th February, 2016, 11:52 PM

Hi!
Yes, problem is surely inside ECU (TEMIC).
I also think the problem is on the injector supply and I started from the electrolytic capacitor. I have to test if it works with new ones...but I'm not so sure the problem is there.

It seems the voltage supply is the one for all 5-6-7-8 injector (and a separated one for 1-2-3-4) and they also share the same controller and comparator chips.
The problem must be around here and I will try to find it step by step.

Really thanks for your help and availability but I want to try to solve it by myself.
I'm not doing it as job but just for fun and experience.
I was just searching for a tip to start with.

Best regards, Lorenzo

**Jan1980** · 9th February, 2016, 12:06 AM

I always do the following step. I am using a multimeter adjusted to autorange AC-voltage. Then, measure ac voltage on the individually injection pumps. You will see the difference directly !! On the non working cylinders are always the same low voltages. On the working cylinders, always the same right voltages.. Easy and fast ! Just remove the intake manifold..

Of sure, you can use an oscilloscope, too...

**megapioz** · 9th February, 2016, 08:23 AM

Hi Jan,
Thanks for your suggestion!
I'll try with the multimeter and after that i'll probe the oscilloscope to a working and a faulty channel and see if the problem is on the driver side or in the power supply of the injectors.

My biggest doubt is that ECU returns fault on just cylinders 7 and 8 (I should do your test before saying this...), but looking at the circuit I realized that 5-6-7-8 cylinders share the same supply and the same driver chip. So it is a bit strange that 2 cylinders seems to work and two do not when they use almost the same electronics.

Next days I will try to check voltage on injectors like you said.

Thanks so much. Greets, Lorenzo