ECU Fault ( I think)

[Ted_BNJ]

Hi.
I have a 1987 325i auto, crome bumpers, and a Motronic 1.0.
Had a period of intermittant engine cut out. Now she will not start at all. Spent time checking all items connected to the ECU, everything seems okay.
I have a spark at each plug and fuel manifold pressue about 35 psi. When I check the injectors, I have 12.8V on the live connections, but the ECU will not provide the 0V required to open any of the injectors.
Has any one got any ideas as to what I should check before I think about repair or replacement of the ECU.
Ted

[BenHar]

Check here if you haven't already: https://www.e30zone.net/e30wiki/index.p ... oubleshoot

And here for Motronic 1.0: https://www.e30zone.net/e30wiki/index.p ... tronic_1.0

Ben

[Ted_BNJ]

Thankyou Ben for the information.
I have read both web pages.
I have a spark in all 6 cylinders and both fuel pumps are running providing a fuel pressure of 35 psi in the injector manifold.
i just can,t get the injectors to open, unless I earth the 0V terminal(s) on th einjectors manually, with the ignition on.
Has any one got any ideas what I could check next.
Ted

[Speedtouch]

I gather the Motronic 1.0 has two crank position sensors (CPS), and the one in the gearbox can fail/fall off, so check you're getting correct signals from those:
https://www.e30zone.net/e30wiki/index.p ... ion_Sensor

[Ted_BNJ]

Thankyou for your reply Maurice.
Yes you are correct the Motronic 1.0 on my Beemer has two sensors. An engine speed sensor and a crank position sensor.
Static tests show both have a resistance of approx 1.1 Kohms,
When I set my Fluke to read frequency and crank the engine, I get 3-4 pulses per sec from one sensor and approx 350 pulses per sec from the other.
That sugests to me that both sensers are okay. But I am not sure, I imagine people who know what they are doing use an oscilloscope, somthing I don't have.
So its looking more and more like the ECU has a fault. Unless someone can come up with another suggestion.
Regards Ted

[Ted_BNJ]

Hi. Re my 325i ECU wiring.
There are a couple of connections between the auto transmission control module and the Motronic 1.0. I am not sure of their purpose.
Can anyone enlighten me. These connections are on pins 10 and 28 of the Motronic. see attachment.
Regards Ted.

auto_cont_M1.0_int.jpg

[flybynite]

I think 10 is earth, not sure about 28 as I don't have a motronic 1.0 ecu pinout to hand. Is it a switchable auto?

[Ted_BNJ]

Hi Flybynite, thankyou for your reply.
I have seen some Motronig 1.0 pinouts that show 10 as chassis, usually on manual box. I don't think it is earthed on autos.
On my beemer I get 178 K Ohms to earth from pin 10.
Yes it is switchable, E / S / 1-2-3. that switch does not appear to have any effect on pin 10.
Regards Ted

[Ted_BNJ]

Hi all
Slight change of tack, has any Zoner fitted a Megasquirt to an automatic 325i
Regards Ted

[Speedtouch]

You could get one of those cheap £20-odd pocket oscilloscopes from E-bay, etc...

I take it you've checked all the earths, particularly relating to injectors and ECU, and that the engine-to-body earth strap is in good condition?

[Ted_BNJ]

Thanks for the info speedtouch.
Didn't realise an oscilloscope was available for that price, Chinese I gess, will have a look on E-bay.
I have checked all the earth pins on the ECU and they are all less than 0.5 Ohms to chassis. and the engine earth strap is sound.
I think I will physicaly check the injector wiring loom again just to be sure.
Regards Ted.

[Speedtouch]

Yes, I've owned such a Chinese pocket scope for a few years and it's still working! Seeing as you're in SE London, you could try giving the likes of BM Sport in Bexleyheath a shout: https://www.facebook.com/bmsport/?locale=en_GB

[Ted_BNJ]

Hi
That must be where Sanspeed used to be.
I will be in Bexleyheath later this week , I may well pop in.
Thanks Ted

[Ted_BNJ]

No i'm wrong Sanspeed are still there BM are just up the road. Ted

[Speedtouch]

Cool, glad to be of help. There's also D&T Wise in the same area.
https://www.facebook.com/dtwise123/

[Ted_BNJ]

Thanks for your help people.
Fitted a second hand ECU today, she fired first crank.
Regards Ted

[martauto]

Thanks for your help people.
Fitted a second hand ECU today, she fired first crank.
Regards Ted

Glad it`s all sorted mate

Mart.

[Speedtouch]

Good to hear that, Ted! May I ask, where did you find the ECU in the end?

[Ted_BNJ]

Hi
Used Brutus he is in Tottenham N17, (Breakers)
I have found him reliable in the past.
Regards Ted

[Speedtouch]

Ah, good for Zoners to know about - thanks.

As flybynite said in your Intelligent Battery Chargers thread: "I would guess that if you opened your old one (ECU) it would simply be an old failed component, dry solder joint or a bit of moisture corrosion".

[Ted_BNJ]

Yes. it looks as if the old ECU has experiance overheating a section of the top board has changed colour.
I wont worry about the current ECU failing.
I think Brutus is a Zoner. That is how I contacted him (2 or so Years ago)
Regards Ted

[Speedtouch]

Indeed, that would explain it - though it may be repairable still...

[martauto]

Yes. it looks as if the old ECU has experiance overheating a section of the top board has changed colour.
I wont worry about the current ECU failing.
I think Brutus is a Zoner. That is how I contacted him (2 or so Years ago)
Regards Ted

Brutus is a cool guy, trustworthy.

Mart.