Need advice on broken reference sensor stud.
 

One of the reference sensor studs is broken. I must have inadvertently bumped the flywheel at some stage.

I'm lifting the engine in tomorrow, so there is no time for me to get a new one. Couldn't I just cut the head off a standard 6mm bolt, grind a slot for a screwdriver and use that instead? Are there any reasons why this shouldn't work?

Please point to the stud you refer to:

http://forums.pelicanparts.com/uploa...1276348878.jpg

No. One of the stud on the flywheel. The ones without a head that stick out 5mm for the sensors to pick up.
No. 23 in this pictrure
http://www.pelicanparts.com/cgi-bin/...Item_Number=23

From what I understand about the flywheel reference studs on the flywheel, they are a special steel/magnetic specifications. Not the standard steel.

They are chemically bonded/glued to the flywheel and very hard to remove if you snapped it off.

Another member could offer more information.

GL
John

I will have to drill it out to remove it.
If they are a special magnetic steel then how can the other identiacal sensor count the teeth on the starter ring? Are they magnetic too?

I have the pin out. It does have a slightly different colour from standard bolts. It is magnetic though, so I don't think it is stainless.

I really hope someone has the answer because. I really don't won't to have to do this one over, and I am all set to mount the engine.

George at 944 Ecology Porsche Parts is a great forum member.
He would be the one I would email.

GL
John

To generate a current in the reference sensor you need a magnet creating a field that moves across the coil in the sensor.

I think that you should take a step back and get the correct part for that stud before you go through all of the trouble of installing the engine.

You will need to put it in to the prescribed height in the flywheel, so at a minimum make sure that whatever you do you leave room to put a new stud in and be able to measure the height accurately.

Keith

+1^
Thanks Keith for the information.
John

Thanks Keith and John.
It will take weeks to get that part over here.

I'm not so sure you need a magnet to pass by the magnet in the sensor to generate current. When I said the pin is magnetic I meant that it can be picked up by a magnet, it is not a magnet itself.

I have a friend who has an ocilloscope. Tomorrow I will run different materials past the sensor and check the readout. I'll let you know what I find.

Thanks Keith and John.
It will take weeks to get that part over here.

I'm not so sure you need a magnet to pass by the magnet in the sensor to generate current. I think passing metal through a magnetic field generates current.
When I said the pin is magnetic I meant that it can be picked up by a magnet, it is not a magnet itself.

I have a friend who has an ocilloscope. Tomorrow we will run different materials past the sensor and check the readout. I'll let you know what I find.

The stud is steel. The reference sensor is magnetic. The sensor produces voltage, when the stud passes it. If you watch the signal coming off the reference sensor on an Oscope it will produce AC voltage.You will have to move the steel very quickly past the sensor, It may be hard to do on a bench test. This type of sensor is very common, it's used on several different manufacturers, and is also used on ABS sensors.
That being said, you want to make sure to use a type of material that doesnt erode, or corrode away, because the air gap has to remain constant , you dont want your new stud to rust away slowly and give you problems down the road.
I would try to find a new one or make sure to put a non corrosive coating on your new fabricated one, paint would probably work, or maybe some rust converter.

Dave

VB_Racing, Dave, is correct.

The stud must be a ferrous metal---preferably unhardened ----see attached link.
The reference sensor is a wound magnetic pickup----see attached link.

http://www.windrock.com/support-files/A6012MAN.pdf

The flywheel stud must be heated to be removed. I used a propane torch. The bonding material was "white" substance. A 3mm hex is used.

http://forums.pelicanparts.com/uploa...1276452543.jpg

Stud removed to show bonding material.

http://forums.pelicanparts.com/uploa...1276452628.jpg

Measurement of stud. 16mm.

http://forums.pelicanparts.com/uploa...1276452662.jpg

Thanks to VB_Racing for making me find out more about the stud.

bubbetufs, I hope this helps you. Pelican does sell the stud or I am sure any inport junk yard with Porsche or BMWs would have a FW with a useable stud.

VB_Racing welcome to the forum. Are you connected with any of the many VB racing sites I found on Google?

GL
John

Not to hijack the thread, but no, not really. I have been involved in engine building for quite awhile, I am a Ford senior master tech, and have worked as a technical consultant with quite a few manufacturers,including VW,Audi,and Porsche.I have worked with alot of 4 stroke MX and Flat track racers(motorcycle) with their engine programs(Hence VB Racing). I have raced motorcycles , carts, and cars for many,many years at an amateur level, with pretty good success. I am just a huge gearhead, that HAS to know how stuff works. I have never driven a Porsche competitively, but raced a few Ford Mustang's in the past. I have owned 3 944's. A 1983 944, a 90 944s2, and now an 87 944s. I like the "overengineered" way these cars are built, and it gives me a break from what I work with everyday.

Thanks for the welcome, been lurking for awhile.

As far as the stud, you should be able to go to a hardware store, and get a 3mm set screw, use red loctite, or what the factory used, which is probably yellow loctite, or bearing lock. I would personally just use red loctite.From the looks of John's there is nothing special about it, just make sure it is ferrous(magnetic).

Dave

Thanks guys.
I made a new stud from a spare 6mm bolt. The broken stud turned out to be for the diagnostic sensor and not the DME sensor, so I'm good to go. I ran out of time however, so I'll have to wait another week which is very disappointing. Engine is sitting on the floor next to the car ready go in.

I know that feeling. I've been futzing around with my 931 for what seems like an eternity.

Here is my round with the studs

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/300125-no-start-944-a.html

Thanks for the link.....

You were fortunate to get the stud out and replaced. On my old flywheel, I snapped the first stud before I got out the torch and nearly made the second stud glow in the dark before it came loose.


SoCal Driver taught me alot in his many great posts.

John