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dazh90

Has my Ref Sensor snapped my Trigger pin? - 525e/535i EU M20B27 [Solved]

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Hey all,

 

   So my eta 525e AUTO still refuses to start (from my previous threads). Changed almost all the ignition components, distributor cap, ECU, relays, sensors, etc etc. I still do not have any spark to the plugs hence  a healthy turn over but no idle. 

   So, i finally had a look into the bell housing where both the Speed sensor, and the Reference sensor are positioned. Because this was new to me when i first had the problem, i'm going to give as much detail as possible with the hope someone may stumble upon this thread in the future. The Speed and Reference sensors push into the bell housing of the gearbox between the torque converter and the flywheel/ring gear. They are both side by side on the nearside of the car, behind the airbox. They are both connected to the engine harness and these connectors can be accessed by removing the airbox and can be seen attached to the block side by side. Grey connector plugs into the sensor pushed into hole B and the black connector connectors to sensor pushed into hole D. Both sensors are the same part number (12141710668) and are interchangeable but you can not get the connectors confused as they must go to the correct sensor relative to the hole identified by B and D.

    This is what i can see when i look into the reference sensor hole and a i believe my trigger pin has snapped because everything else has been changed and i get quite funky results when the engine is turned over and a AC Volts are measured across the sensor. See Duncan's amazing guide on how to check this if you do not know already below. MASSIVE thanks to Duncan for this, has helped me and tonnes of other people.


So the sensor that i discovered was faulty was the reference sensor, which goes into the hole closest to the road. The lowest hole. This sensor was absolutely shot, it had no resistance so was not detecting anything. I changed it for a working new one which i can confirm works as it was tested in a university lab using an oscilloscope. Correct resistance and AC sine wave replicated by a spinning neodymium magnet. This has not solved my issue so this is what i see when i look into the hole. I need help and peoples experienced opinion on this as its the first time i'm investigating it:

 


 20160723_181810.thumb.jpg.30ecc8c9741a13

 

Now analysing this photo, reveals to me.... this does not look right. Although it does not look aggressively snapped, it does not look long enough!? The only angle i could take the photo forces it to be taken bias to the front of the engine so you can even see the ring gear. If you look at it from the angle the sensor would read, you can barely see the pin! I've drawn out roughly what you would see if you looked at it head on..

20160724_085140.thumb.jpg.1c1b1a47c7ba72

 

So, does everyone agree that this does not look right? Has my pin snapped or is this normal? As the flywheel rotates, it will not swipe across the sensors face/tip. 

   Also, an interesting observation i made of the old, faulty sensor backs up the theory that the pin has snapped. The old sensor has swollen out creating a dome to its face (interesting?...). There are also scrape marks on its face and a dent to suggest its been grinding against something.

 

20160724_090715.thumb.jpg.674d6cb0618ba7

20160724_090636.thumb.jpg.b10caa65d6e524

 

Wondering if anyone know about this, if they have changed a flywheel on these cars. As the engine rotates and you pass the trigger pin on the flywheel, you periodically come across large tabs of the flywheel that pass by the sensor which are NOT trigger pins. They are just large areas of the flywheel that match the length of the trigger pin. These have long scratches on them like the rust of the wheel has been removed. Long lines of exposed fresh metal as if the sensors swollen tip has made them. 

20160724_090741.thumb.jpg.ea02c04ea06648

 

So, that is where i am at currently. What do people think? Is this enough to pull the transmission out and replace the flywheel? Has the trigger pin snapped off? Is this normal what i am showing and if so, where would my next area of investigation be? Is changing both sensors enough to move on and look elsewhere? 

ALL help and opinions are immensely appreciated, i really am stuck. I also hope some of this information will inspire someone else with the same problem and help them repair their own fault!! 

Kindest regards,
Darren - From Brighton, UK

Edited by dazh90

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Could you use an endoscope to have a look first? Easier than pulling the box

It's plausible the pin has snapped but I'm not sure what it should look like TBH. Tims has my old flywheel so maybe he could post a picture of a good one?

Obvious daft question you haven't swapped sensor leads over have you?

Sent from my iPhone using Tapatalk

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4 hours ago, duncan-uk said:

Could you use an endoscope to have a look first? Easier than pulling the box

It's plausible the pin has snapped but I'm not sure what it should look like TBH. Tims has my old flywheel so maybe he could post a picture of a good one?

Obvious daft question you haven't swapped sensor leads over have you?

Sent from my iPhone using Tapatalk


Hey Duncan,

    The plugs are on the right way as i found your original thread where you are investigating what order they are connected :) " Grey connector plugs into the sensor pushed into hole B and the black connector connectors to sensor pushed into hole D "

 

It's difficult to know what it should look like as there doesn't appear to be alot of info online about this problem (or from what i can find)

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Worth swapping over "just in case" to rule out the obvious.

I've heard of a dropped pin but know nobody who has suffered.

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Hi Darren,

i have not experienced this myself but have read someware else that the pin can fall out but have not heard of it snapping however if it has snapped there could be something else in the bell housing that has done this as I would have expected more damage to the sensor. A little searching shows that some of these are a dowel type of trigger pin and others are a welded trigger pin.

 

On my M535i of which I recently changed the gear box there is quite a large alloy inspection plate that can be removed from the bottom of the bell housing to gain access to the torque converter and this would give you good access to inspect the ring gear and trigger pin assuming the 525e has a similar set up with regard to six cylinder engine and 4 HP 22 type gearbox.

 

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Hi folks,

   Thank you very much for your replies! 

On 25/07/2016 at 9:53 AM, dan101smith said:

I've got a 525e engine with the gearbox off, let me see if I can swing by and get a pic for you.

If you could do that for me Dan, i'd appreciate it greatly! It's difficult to diagnose it when you don't have anything to reference from. I can't seem to find a definite image online of the pin :/ 

 

 

On 26/07/2016 at 11:23 AM, garym535i said:

On my M535i of which I recently changed the gear box there is quite a large alloy inspection plate that can be removed from the bottom of the bell housing to gain access to the torque converter and this would give you good access to inspect the ring gear and trigger pin assuming the 525e has a similar set up with regard to six cylinder engine and 4 HP 22 type gearbox.

Yup, found it :D

20160729_143736.thumb.jpg.01fb6aa95141ab

20160729_143835.thumb.jpg.766d3666c2b678

20160729_143851.thumb.jpg.2a1e6bf9d5ff27

This thing is so short, it won't swipe past the sensor..... 

This is the only image i can find that tells me this thing should be longer although the flywheel does not look like the one installed originally by BMW, it does look like an aftermarket part:

flywheel_auto_ref_pin_text.jpg.cf7869e12

Edited by dazh90

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3 minutes ago, Sir Anthony Regents-Park said:

That has indeed snapped off - but you can buy another flywheel, remove the pin and weld it to your flywheel - sod taking the gearbox off just for that. On manuals, the pin is held in by a tiny roll pin that can be drilled out.


Thanks for your input Anthony, very much appreciated 

   I too believe it's snapped off and dont much fancy taking the transmission off (as im currently broken down on a main road with busses driving alongside the car within a meter or so). My current idea is to make an L bracket out of some mild steal and weld it to the area you can see on my photo. Grind off the existing broken pin and replace it with the L bracket so it swipes on past the sensor nicely. What do you think of that idea, in your opinion? Currently waiting on a mate to send me the actual length of the pin from his 525e breaker car.

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[Solved]

   Hey Folks

So the issue was indeed a snapped flywheel pin. I hope this thread helps out others in the future, as i found no info on it online so i feel bound to duty to report the symptoms (above) and the solution that i found worked really well. 

Hard to see but, the pin should look like this;

7168612867837U_1.jpg.e5add671b0107b2ac45

 

and mine looked like this;

20160729_143856.thumb.jpg.3369d869b65711

 

My solution was to get a strip of mild steel from BandQ which was 10mm across and 2mm thick. I made like an "L" bracket, shown in the photo below. It's important to imitate the original height of the pin which i got from a friend who brass rubbed his pin from a working 525e. The height is 15mm. 

20160808_154706.thumb.jpg.8f48de432ad7c6

 

Then welded it in place. I got it to stay in place by putting a TINY dab of super glue on the back in. If you use this technique, be careful not to use too much glue as it will contaminate the weld so literally... right at the back where the weld wont really hit and if it does, it wont matter too much. 20160808_171937.thumb.jpg.7b777cb107b17d

 

Then used a dremmel to grind it back so it wont hit the sensor when it rotates. Trial and error for that part. Slowly rotate the engine and listen out for any contact. I used a sharpy to coat the pin and observe if there was any scratches to the ink upon rotation. 

20160808_175304.thumb.jpg.d96977123b4fb2

 

So far, no reported problems with the starter motor hitting the weld as it slightly overlaps onto the teeth. Seems to be okay and works fine now. Also applies to the 535i.

 

Happy E28 again! :D

 

20160809_174812.thumb.jpg.318e8eb10e09a5

 

As i said, hope this helps someone out there who is having a 'no start' problem and has done what i done which was changing the ECU and all the sensors etc. Don't assume the pin is intact although... probably chances of the roof falling off the car is more likely than the pin snapping or falling off haha! 

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