Flywheel position sensor connections

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randall977
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Flywheel position sensor connections

Post by randall977 »

I've recently bought a 1982 project CSi which has been off the road for 9 years. When I connect the battery the computer display flashes across one LED digit at a time quite quickly - could this be the battery damaged SI board in the dash? Other likely causes?

Also, the garage who had the car stored for many years cut the two connectors off the loom for the speed and flywheel position sensors - I know which of the three wires is the earth but not which way round the other two wires go - does it matter? Is there a way of identifying which connector goes to which sensor?
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baders
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Re: Flywheel position sensor connections

Post by baders »

First question is, does the car run ?

The speed sensor reports engine RPM to Motronic ECU. It normally has a black plug. The reference sensor determines crankshaft position and is normally a grey plug. Yours have been replaced, so it may be a matter of tracing (belling out with multi-meter) back to the ECU to identify which is which. This orientation matters greatly. As these sensors are both inductive pick up types, plug wiring orientation of the black/yellow wires should not matter.

What you need;
1) Correct year ETM (Electrical Troubleshooting Manual)
2) Multi-meter.
3) Bosch Motronic Basics guide - http://www.hiperformancestore.com/motronic.htm (Edit. This seems to be down atm).

For the OBC, do you have the owners manual ? There is a reset sequence in that document.
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randall977
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Re: Flywheel position sensor connections

Post by randall977 »

Thanks for the reply. No not running yet, the garage owner thought the sensor was the problem - shame he removed and threw away the connectors! The connections in the photo are new ones I've made with the proper contacts and new sensors (I tested the old ones and one sensor was faulty).

Obviously the problem I have is that unless I know I have them the right way round I won't know if that's the problem or something else. The easiest solution is to try staring it and hope nothing else is wrong... I'm nearly at that point.
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hornhospital
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Re: Flywheel position sensor connections

Post by hornhospital »

The sensor end is the one that deteriorates and crumbles. I don't believe the plugs were cut off, but disintegrated like all of them do. The sensor mounting holes on the bellhousing are marked "B" and "D". The "B" one is the lower of the two (further around the bellhousing). B is the speed sensor, D is the reference (position) sensor. The black wiring harness plug goes to the B sensor, the gray harness plug goes to the D sensor.

You'll have to peel back the sheathing on the sensor end plug to determine which is the black and which is the yellow wire connection. Yes, it matters. I have a picture of the connections and associated wire color somewhere, but cannot find it. I believe you have them connected correctly in the photo (yellow to the center) but I don't know which of the outer pins takes the shield and which takes the black wire.
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'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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randall977
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Re: Flywheel position sensor connections

Post by randall977 »

Thanks for the reply - very helpful. I have one of the old sensors so can peal back the sheath on that one - I didn't think the colours would match.
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randall977
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Re: Flywheel position sensor connections

Post by randall977 »

Good tip - I can confirm yellow is the middle wire. Earth is quite easy as you can test it with a multi-meter.
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sansouci
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Re: Flywheel position sensor connections

Post by sansouci »

Molex makes a variety of multiprong male/female connectors. See the post on bimmerforums:

I found a Molex "Plug Housing with Integrated Seal- Valueseal" Numbers 172877-0002 and 172878-0002 which can be bought through Digikey. Molex has great product drawings. Only question is how the wire is fixed to the connector. It mentions "terminal series 173041 and terminal series 173042" It seems that the plug housing holds the terminals. Wire can be 16 or 18 gauge. BTW, the body side connector is OK, it is the wheel side that got damaged. Will report back as I know more. I am hoping that crazy glue will put the broken piece back together.
Otherwise, the terminals are $0.11 each, the 172878 is $2.03 and the 172877 is $1.81, plus Digikey's S&H. Cheap if it works as Molex Value Seal video says it is waterproof.
Cheers!
Sansouci
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