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Engine does not start

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sskang
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Engine does not start

Post by sskang » Wed Sep 01, 2021 5:52 pm

Hello everyone,

It certainly has been some time since I last posted here!
A lot of water under the bridge, broken engine that took close to 3 yrs to repair, then Covid19.

I would like to ask for the members help to a problem which I have never encountered before.

Since about a month, I have had days in which my M6´s engine would cold start, but die out shortly after.
Sometimes a repeated attempt to start would succeed and the problem does not appear when engine is warm.
I asked a local electrician what it could be, since ADAC diagnosed upon his visit that the ignition signal was not coming.
He said, perhaps the reference sensor was failing so I replaced them both with new original Bosch.

The problem was NOT resolved and now, the motor does not start at all.

My hunch tells me that it may be the Motronic, but before I send it for repair to a specialist,
I wanted to do as much as I can before the repair and I have some questions hereto.

1. Is the M635 (055) and M6 (079) interchangeable since I have a spare 055? (My car´s 02 sensor is not active)
2. What could be the potential culprit? (I´m guessing either the DME, the fuse box, or the wire harness)
3. Has anyone experienced a similar problem?

Many thanks in advance for your help!
Any information would be much appreciated.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

rs6
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Re: Engine does not start

Post by rs6 » Wed Sep 01, 2021 7:39 pm

Might be dumb but:

Did you try to swap both connectors when the sensors are? Those 2 which goes to gearbox bell? Did you bought OEM/ Bosch?
I had sensor from alfa- same product number and it was rubbish..
Then try to bypass ECU for code ignition start
check the Spark plugs/ injectors

Is fuel pump turning on?

About the fusebox. I doubt that there is something wrong with the fusebox unless something happened to it.
Smell it closely, if fusebox have burnt smell, then it's faulty. But I think also other things wouldn't work.
You can check the relay under the dash and relays in the fusebox..

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sskang
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Re: Engine does not start

Post by sskang » Wed Sep 01, 2021 8:00 pm

Hello rs6,

I have checked the fuel pump relay and they seem to be in working order.

The 2 reference sensor connectors have been connected properly, hence not the issue.
Fuse box probably also not the culprit.

This is why I assume it is the ECU/DME.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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hornhospital
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Re: Engine does not start

Post by hornhospital » Thu Sep 02, 2021 2:05 am

Semi-educated guess (some would disagree :wink:): the ECU has a failed solder joint or two. It would start with difficulty when cold, but when warm it work and started normally. The solder joints in the ECU/DME is a known trouble spot. When they crack you get connections randomly according to the ambient temperature. Warm, the traces/joints expand and make contact. Cold, the traces/solder joints contract and you lose connections.

You can reflow the solder joints if you feel capable of handling a soldering iron
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"; '95 318is "Bebe"

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sskang
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Re: Engine does not start

Post by sskang » Thu Sep 02, 2021 7:20 am

Hello hornhospital,

Damaged solder points causing issues is a known problem to me from the forum here.

IIRC, there was a tech article about how to resolder the solder points but I am not very confident with a solder iron and the 079 ECU is NLA so I would like to avoid the risk of damaging the ECU.

I will probably have a specialist examine it.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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sskang
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Re: Engine does not start

Post by sskang » Fri Sep 03, 2021 7:49 pm

Status update

I did a little experiment to see whether the ECU was the culprit.

Before taking her out for a ride, I turned the IGN and left it ON for about an hour to let the current flow.

I then attempted to start the engine and it started after short cranking!

It is becoming more certain that the ECU may be at fault.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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sskang
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Re: Engine does not start

Post by sskang » Thu Sep 09, 2021 12:17 pm

Status update

I've taken my M6 out for a drive twice since my last report.

During the first drive, the symptom resurfaced but after a short attempt, the engine started.
On my second drive, the symptom did not occur and I could drive it very normally.

After contacting a BMW dealership specializing with youngtimers where my friend had a positive experience,
I contacted the workshop meister and he gave me a contact where I could have the ECU repaired.

The first contact did not offer the service I was looking for, so I was back to square one.
The meister gave me a second address where the desired service could be rendered,
but I was extremely disappointed by the receptionist's unfriendliness so I decided to ditch them.

The journey continues...
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

bpoliakoff
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Re: Engine does not start

Post by bpoliakoff » Thu Sep 09, 2021 5:24 pm

Try fuel Injection Corporation. I had called him years ago about my early ecu wanting to make sure it was good. He said the early ECUs rareky go bad and to save my money and was willing to spend a few minutes on the phone with me. Pretty honest it seems. I have also seen positive feedback for him on other forums. He is located in Tracey CA
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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sskang
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Re: Engine does not start

Post by sskang » Fri Sep 10, 2021 2:27 pm

Hi bpoliakoff,

Thank you for the tip!
I am trying to find a specialist in Germany where I currently live since I do not want to ship the ECU internationally.

The parcel service here is terrible and would like to avoid the ECU being lost in Transit.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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635sharknose
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Re: Engine does not start

Post by 635sharknose » Fri Sep 10, 2021 4:20 pm

Paul
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1987 635CSi Bronzitbeige

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sskang
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Re: Engine does not start

Post by sskang » Sat Sep 11, 2021 2:24 pm

Hello Paul,

Thank you so much for the info!
This specialist is located not so far from where I live.

I will give them a call and inquire about the repair, and will write a brief update here.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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635sharknose
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Re: Engine does not start

Post by 635sharknose » Sat Sep 11, 2021 2:55 pm

Super! I'm glad it helped you :D
Paul
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1987 635CSi Bronzitbeige

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sskang
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Re: Engine does not start

Post by sskang » Wed Sep 15, 2021 9:34 am

Status update

I took the M6 out again for a drive on Sunday, and before the ride I left the ignition on for 1 hour.
The engine started normally and the problem did not surface.

Yesterday, I wanted to give my car a wash so this time, I left the ignition on for 30 min and started the motor
but the symptom surfaced, couldn't start the car after the motor started and ran for a few seconds.

Paul

I have contacted the specialist you gave me and in fact they are located quite far from my home, but they were much pleasant to talk with.
However, the reply I got was more or less the same, the specialist must inspect the ECU first and a cost estimate will be issued,
which based on their experience could be somewhere between 100 - 600 Euro.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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635sharknose
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Re: Engine does not start

Post by 635sharknose » Wed Sep 15, 2021 3:24 pm

Where are you located?

Is this more in your area?
https://www.actronics-gmbh.de/bmw-steuergerate
Paul
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1987 635CSi Bronzitbeige

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sskang
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Re: Engine does not start

Post by sskang » Thu Sep 16, 2021 7:11 pm

Paul,

IIRC, you helped me with the headlamps!

Thank you for the referral.
They were savvy about the ECU ignition signal failure.
Although they only accept repairs from workshops, I will
have it repaired via my friend here.

I live in Düsseldorf BTW.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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sskang
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Re: Engine does not start

Post by sskang » Tue Nov 30, 2021 1:57 pm

My apology for the belated update but the ECU was sent to AC Tronics (Germany) for repair.
They were quite competent and I received the repaired ECU back within 10 days after shipment.

One minor complaint I have with them is that there was no explanation with regards to
what was the cause of the failure. However, when I called them and asked what the issue was,
the staff checked the log of my ECU repair and told me that there was a crack on the PCB
where the ignition signal was being transmitted.

The crack was soldered upon repair.

After mounting the ECU back in the car, the motor started as usual, with no problem and
since the repair, I have not experienced previous issues I had.

Many thanks for those supported me upon getting the ECU repaired.

For anyone experiencing the same issue, I can recommend AC Tronics as their repair cost was 50% less
compared with other similar ECU specialists.

The cost was €190.
sskang
1987 M6 Alpinweiss
Tokyo, Japan

"Aller guten Dinge sind Sechs"

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635sharknose
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Re: Engine does not start

Post by 635sharknose » Tue Nov 30, 2021 5:38 pm

Good news! I think that is a very reasonable price for the repair.
Perhaps I might need them one day as well, it's not that far for me, they are near the border between Holland and Germany.
Paul
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1987 635CSi Bronzitbeige

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