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 That sensor has been superseded with a two wire sensor that uses a dedicated ground wire instead of the previous single wire grounding through the engine.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

Any decent shop or electronics person can change that connector. And the pin crimp-er tool is nice but not required. The pins can be crimped carefully with needle noose pliers and then soldered and shrink tubed. Again, decent electronic skills needed here.

You don't need a pin extractor tool if you plan to replace the pins and the connector, you should replace both. Just cut the old connector off and install new pins then seat them into the new connector. Also worth mention is that those wire harnesses have a shielded braid that MUST be also connected to a pin.

I could have sworn I found the harness side connectors here on the host, but can’t locate now?

I believe you are searching for 022-906-233-B Electrical Terminal Housing (3-pole).

Thank you! My Pelican-Fu is improving, but I still get lost in the weeds occasionally... :)

These connectors are called 'Junior Power Timer' or 'JPT' and the one you need is 3 pole.

Search for "junior power timer connector 3 way" you will find them.

Jae Lee built a 3.4 for my 1987 nine months ago and ever since the rebuild, I've been having a hot start issue. For around ten minutes post a full operating temp shutdown, the engine will crank, but will not fire. If I try to start the car immediately after shutdown, it just cranks. One minute later, it just cranks. Five minutes later, it just cranks. Ten minutes later... It starts.

Car runs GREAT otherwise.

We tried a new two wire CHT sensor, but that didn't solve the problem (switched back to the previous two wire CHT) and I've been casually troubleshooting the issue, including unplugging the CHT sensor and jumping the CHT sensor (no change in either case).

The motor has an @salcarceller MAF / injector / ECU setup, but that was on pre-rebuild and the hot start problem started with the rebuild.

@KTL your BMW flywheel set screw issue is interesting. We did replace both flywheel sensors, but we also installed an Aase lightweight flywheel as part of the build.

I wonder if my issue is heat related with the set screw or set screw sensor. Could the gap grow enough at full operating temp to cause the no-start, but 10 minutes later shrink enough to allow starts?

I believe I need an oscilloscope to test the flywheel sensor outputs? Alas, I don't have one and I wouldn't know how to use it if I did.

Apologies for the tangent here.

You can test the sensors with a multimeter for resistance any open shows bad, i heard you can check with the ac function and crank the engine should show some AC voltage

Do you have spark during the no start? Just remove center wire from Dizzy and put a test plug on it, does it spark during cranking?

If you have spark then your Flywheel Sensors are fine.

If you have spark, then spray 2 shots of starter fluid into the intake and try starting. If she catches you have a fuel issue!

On my to do list (after I find a test plug and purchase some starter fluid).

Like I said, I've been *casually* troubleshooting! It hasn't been a huge issue, save for fueling up on the back end of a drive. On the front end, I can start the car, drive a few miles to the gas station, shut it off, fuel up and it starts right up again, no problemo.

I am extra diligent about not stalling the car in traffic though. That would SUCK!

I don't think the heat is great enough to cause the air gap issue with the reference sensor. We've run our Carreras on the track on very hot days and never encountered any hot no-start conditions

When you guys did the rebuild, did you install new reference sensors or reuse the old? I'm just wondering if they are old enough to have some issue with the wiring itself. Try messing with the two black connector wires where they lead out to the actual sensors on the back of the engine?

How old is the fuel pump? They can be pesky with age as well.

We did replace both flywheel sensors with new Porsche parts.

As far as I know, fuel pump is original.

I've got some troubleshooting to do. I've just been having so much damn fun driving the car.

Thanks for the ideas!

Revised diag steps:
- During no start event
1. Turn key to RUN but do not start engine, then verify that the idle control valve is vibrating and humming.

2. Test for spark

3. Spray starter fluid into intake

Do them in that order, if one of those steps fails do not move on to the next step.

To reduce possible pin corrosion in this often-times wet environment, apply dielectric grease to those contacts.

Sherwood

I had one pair of sensors that only lasted a few years. After those few years it was like the car was haunted. The sensors would read fine with a ohm meter when cold. Once they warmed up they would on occasion get flaky. I finally replaced them after every other test and that solved my problems.

Once removed it was easy to test them hot and one of them would cut out. It was weird. I was happy to throw them out.

Thanks Glen. When I wondered earlier in this thread if I had a heat related reference sensor issue, I was thinking more along the lines of intermittent sensor issue vs sensor gap growing beyond 0.8mm spec.

FWIW, I replicated the issue yesterday and was able to ascertain the following... 1) thanks to Sal's fuel pump prime feature in his ECU, I could at least hear the pump running during every subsequent restart attempt and 2) I connected my Fluke up to cylinder 3 spark plug lead, to check RPMs, and it showed ~300 RPM during no-start / cranking. I assume the latter qualifies as "having spark."

Will confirm IAC valve operation and attempt starter fluid test next time.

FWIW, here's another thing, while the car is failing starting attempts and when it eventually starts, I smell something difficult to describe and, more importantly, something I've never smelled before in 30 years of being around cars. It isn't unburned fuel. IDK what it is. It's pretty pungent tho. After the car finally starts, the smell quickly disappears.

Anyone have an ECU breakout box I can borrow? OTC 3226, or the like? I'd love to take reference sensor measurements.

https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=DWsearch&LastVisited_i nput=0804&make=POR&description=022906233B

Wow 15 dollars for a 5 cent piece of plastic!

Frank
Does it smell a little like rotten eggs ?

That came out of a mold that cost 100k+, then was packaged, distributed and made available to users in low volume market.

It’s a bit dear, but not when you account for all the factors.

I hear you though, the tally adds up as you start fixing things!!! Eye watering at times...

Not particularly. It has more of an acrid quality.

Also, currently running a pre-muffler, so not a cat issue.

The BMW crank sensors work in the 84-89 3.2L and they are Bosch OEM sensors at reduced price. The part number for the BMW sensors is:
Bosch # 0.261.210.002 about $80

Pelican has them:
https://www.pelicanparts.com/More_Info/12141708619.htm?pn=12-14-1-708-619-M14&bc=c&q=0.261.210.002

The Porsche Bosch sensor # is
0.261.210.005 about $150

The only slight difference is that the BMW sensor harness is a tad longer. I've used the BMW sensors in the past with no issues other than a few dollars saved.