84 3.2 flywheel sensor connections - better way?
 

Good Day,
I have been tracking down intermittent start issues on my 3.2. I believe I have finally found the issue. It is these connections below. I believe it would be the flywheel sensor connection, if incomplete, that would cause a no start. I can duplicate the issue when working these connections/wires a bit, moving them around, etc. I have tie wrapped them to provide a more secure connection. I am thinking dirt and moisture may be getting in as well as the cables seem a bit crimped on occasion.

Is there a better way? Replace all connectors? New bracket? Any thoughts will be appreciated.



Dave

http://forums.pelicanparts.com/uploa...1553891494.jpg

I had an issue with those connectors and ended up cutting them off and replacing them with 3 way deutsch connectors. In mine however the housing of the connector was falling apart and exposing frayed cables. Deutsch connectors were more secure and watertight. Had no use for the factory bracket after that though.

Those are very good connectors but they do suffer from old age. I would remove the connectors, clean up the pins or replace the pins and put them back after you make sure that wires are crimped on tight and there is no corrosion.

The connector you have zip tied at the top is not one of the flywheel hall sensors. That connector is the cylinder head temperature sensor. That sensor has been superseded with a two wire sensor that uses a dedicated ground wire instead of the previous single wire grounding through the engine. Looks like your sensor is a two wire sensor but they still can be problematic. Usually it's a hot condition that affects those sensors.

The flywheel sensors are the both the same sensor but provide different functions in their respective positions. One sensor is a legitimate timing sensor that uses flywheel "teeth" to provide crankshaft angle reference to the ECU. The other sensor is a position sensor and uses a set screw in the flywheel for reference. It's my understanding that this sensor is only used for starting the engine and after startup it's function doesn't affect engine operation. Both sensors are prone to heat degradation since the wire leads are somewhat close to the exhaust heat. The wire sheathing cracks, allowing water to penetrate the internals and you get intermittant behavior. Note there's an alternative BMW part number for these sensors that's half the price of the same Porsche part, excepting a bit longer wire length on the BMW sensor.

We had a no-start issue with an '86 BMW 325e that uses a similar Motronic engine management system. The set screw in the flywheel was installed loosely and the gap was not proper. Thus the sensor couldn't detect the screw and it wouldn't start. Ironically the guy we bought it from traced the same no start problem when he bought it to a missing set screw. He "fixed" the issue with a new screw that eventually came loose again!!! :rolleyes:

The bracket is just a fixture to hold the wires neatly. It does nothing to secure the electrical connections. The connectors themselves are responsible for proper electrical connectivity and they actually snap together very well and are often hard to disconnect.

Sort of looks like the spring clip is missing from your top plug :confused:

The connectors are called Junior Power Time connectors. There may be more manufacturers but I know that TE Connectivity makes them and they are available from Mouser and Digikey.

Great observation!

I just bought two new speed sensors and the two wire cyl head temp sensor - I also purchased the other end of the connectors - I am going to install the three new sensors as well as replace the other end of the connectors so that all is new for the next 35 years!

Where did you buy them? I was specifically looking for the ends that plug into the dome... Do you plan on cutting and splicing or replacing the entire wiring

Sent from my Pixel 2 using Tapatalk

Thanks all for your responses. Yes, the clip is missing on the CHT connector, thus the tie wrap as a backup. That is not the issue as the CHT will still allow for spark. I believe the flywheel sensor wire may be compromised some place out of sight. Do the cables look like they have enough play?

Will have to try to get a visual on it, next time it is up on the lift. Question also is should I replace the wire harness connector.

Dave

I bought the two ref sensors from our host - I had to buy the temp sensor from my dealer. The wiring harness side of the connectors - I found online - I believe with our host or Autohouse ... I am going to remove the old ones, put the new connectors on in place of the old.

If you are planning on replacing the crank and reference sensors you can order Bosch part number 0 261 210 002. Pelican selss them for $73.50 versus $159 for the one speced for the 3.2. the Bosch 0 261 210 002 is a BMW spec'ed part and is identical to the Porsche part aside from the lead being slightly longer.

The BMW “cheat” on Pelicanparts equates to the sensor for 535 cars from 1985-1988 and 533 cars from 1983-1984 which is BMW part number 12-14-1-708-619-M14

Also is the CHT sensor a 2 wire? see if you have 1 or 2 male pins in the white connector. If it's a 1 wire replace it along with the sensors.

When you replace the sensors I suggest you set the air gap for them as well.

The BMW sensors work great, they are exactly the same but the wire harness is a few inches longer. I use these BMW sensors often.

The harness side 3 pin female connectors rarely go bad, just spray them clean with good contact cleaner, then look at the actual female pins to be sure they did not get bent up. If they look good and are clean they are likely good. The male side of the harness comes with the sensors so that will be new.

If you need supplier for Junior Power Connectors see here also:
https://www.corsa-technic.com/category.php?category_id=146

How hard is it to replace the connector at the wiring harness side?

Replace the connector only by using an extractor tool to remove the pins from the old connector. you then just push them into the new connector. https://www.newark.com/amp-te-connectivity/1-1579007-6/extraction-tool/dp/78H0240

However, you might want to replace the pins too. Go this route, you will also need the right crimper for JPT connectors and of course the pins (which are actually called connectors) https://www.bmotorsports.com/shop/product_info.php/xrf/gshp/products_id/4038?gclid=Cj0KCQjw7YblBRDFARIsAKkK-dL1fI2Z_q4pDhc0ap50dPSagiR58rgUZh45TyOYOhjWP9mvCGw WF-0aAo4hEALw_wcB
I don't recall if JPT have water/dust seals too but you will need those too.

So not that easy.

No, its quite easy. Just not inexpensive if you don't already have the tools. You could probably find cheaper crimpers and extractor tools if you hunted some.

My idea of easy is cheap. lol