W108 280SEL 4.5 USA - correct ECU?

Hello,

My name is Alex and I am from Bucharest, Romania.
This is my first post on this forum and first of all I would like to thank the founder and the contributors - the information gathered here is priceless, not available even in USA! This website helped me a lot in understanding D-Jetronic and further diagnosing and testing my 1972 W108 280SEL 4.5 V8 US-version.

THE PROBLEM: during my diagnosis I checked the ECU and noticed it's 0 280 002 004 instead of 0 280 002 005 like it should.
The MAP is 0 280 100 100, the correct one for the 4.5 that from my understanding is supposed to work with 0 280 002 005 ECU.

I must say from the beginning that the engine looks the original M117 4.5 one, it has blue injectors, 0 280 100 100 MAP and most important, 117-984 stamped on the back / driver side.

Thanks to this forum, and Norbert (cheers mate!), the car is running but it still under tests/diagnosis in my driveway and I can not test it on the roads because it has no number plates yet.

How is this 3.5 ECU going to influence running of the vehicle?
Should I get a 0 280 002 005 as soon as possible?

All the best,
Alex

Hi,
there´s only one answer to your question :

Yes, you should get the original ECU for your engine, theres a reason why every Engine has it`s own !

Greets
Christian

Hi Alex,

no doubt, you should get the correct ECU 0 280 002 005 . 0 280 002 004 is different in many aspects. Only a smal one is that it cannot handle full-load contact and expects a type 2 MAP sensor. More important ist that each ECU contains specific adaptation to the engine. In your case the worst is that 0 280 002 005 uses other injectors with higher flow rate. But there are many more different details.

Dear friends,

I would like to update the status regarding the ECU.
So, I was able to change my ECU with the original 4.5 - 0 280 002 005.

Here are the notable differences:
- during warm-up the car has a smoother running
- the idle no longer fluctuates up and down - I thought that my problem for this was the AAV, which currently is not closing sufficient because of the bad thermostat.
- after the car is warmed up, I can now play with the idle screw and see how the idle changes, with the other ECU the idle screw was not doing much.
I will post some videos later with the aspects described above and I hope these aspects are not "placebo".

Now I have an other question: the fuel pump relay is no longer working, I washed the engine compartment and the fuel pump relay was not fixed in the plate behind the ECU, it was hanging upside-down so water entered inside and currently is no longer working.
I took it apart and I will see if I can get it fixed.

My question: what are the consequences of running/driving the car with a jumper wire/bridge between pins 30 and 87 instead of the relay? I know that now the fuel pump is running all the time when the ignition is turned on. Anything else?

Thanks so much!
Alex

Hi Alex,

it is illegal to run with that bridge. Every car must cut off fuel pump when engine stalls since 70s. In case of an accident you can otherwise continue to spill fuel and feed a nice fire. Imagine that you sit inside the car and cannot escape ...

It might also be that you have now destroyed your new ECU. ECU drives the relay that you have put under water.

You make a good point!
Thank you again for the clarification.

I hope i did not hurt the ECU... Even if the sensor was damaged by the water, maybe there must be some protection, a fuse that had to blow?!
I’ll have to check if any fuse is responsable for this relay.

Now... if the sensor, after cleaning and checking, will check out ok, but still wont work on the car then i guess i must verify:

1. If the ecu sends to the relay plug 12 volts for one second when i put the ignition on or when i crank the engine.

2. If there are not 12 volts present, then something must hapened with the ECU.

Correct?
Are there other things to check?

Thanks,
Alex