Hall Sensor??
 

At SITM Wally put the Bosch Hammer to work on my GT, and did find a few faults. I have them all fixed up now, EXCEPT for the hall sensor. The Hammer said that the sensor was shorting out. Wally said that most often the connector has come loose. We checked it, and it appears to be properly plugged in.

Now my question is, does anyone have a good write-up, or pics of the hall sensor system from their own BTDT efforts. I've checked Tony Harkin, John Pirtle, and Greg Nichol's sites with no info found. (other than a post from Wally saying that if the hall sensor isn't working, the EZK retards the ignition 4 degrees!!!!!) Any help steering me in the right direction would be much appreciated. TIA,

Hello Chris,
What information exactly do you want ? Do you have access to a 'scope ?

If you have checked the connections from the sensor back to the ECU, then it looks like you will have to change the sensor.

My understanding is that with a faulty Hall sensor, the igntion is retarded 6 degrees, because without a Hall signal, the signals from the knock sensors can't be processed. So the EZK retards the ignition 6 degrees "just in case" there is detonation.

Let us know what you need to know, and what you are planning to do.

Regards,

Chris,

Could be that there is no articles on it since they rarely go out. Have you checked all of the sensor wiring from the distributor to the controller? This sounds similar to the notorious green wire problem on earlier cars. Since the hall effect sensor puts out such a low voltage, any break, corrosion or loss of insulation can affect the signal.

How are things going in SC? Gonna make it to Hallet?

Dennis

Bigun;

A number of years back a PO installed too long of a smog pump belt on an 88 S4. When fully tightened the smog housing was able to pinch the Hall sensor wire. Everything checked perfectly except for certain driving conditions. As Dennis says, they rarely go bad. Check for wiring first, actually giggle it, bend it... But you really need an oscilliscope to check its waveform.

Another problem that I have seen is fine metal particles and dirt 'sticking' to the sensors magnetic head. Thus rendering it useless. Most likely have to pull the pass. side timing belt cover to check that one. Again, not a common occurrence.

Maybe Dave Chamberlain has some pixs of his recent Hall sensor malady.

Scott
:cheers: to the 89GT brotherhood

Hey Chris,

I have been there in my recent valve repair. It is a pretty simple mechanism..comprised of a metal plate that sits behind the passenger side cam gear. It has a slot cut in it so that when it passes through the sender part mounted on the rear cam cover plate, it can tell what the cam position is. From the looks of it..it appears to be an on/off type signal.....

If you look straight down behind the passenger cam gear cover (the one you pull to check belt tension), you will hopefully see a knock sensor style connector and a holding bracket..very similar to the knock sensor connector/holder up front. It is right up against the engine pull bracket..and you should be able to see the allen bolts that hold it in place.

My connector (from the atual hall sensor) was so fragged that it was able to be put back in the corresponding knock style connector from the harness both ways..(normally this is set up as a one way only...like the injector connectors).

I can't remember if I was able to pull it with the cam cover on or not...seems pretty tight...I think Dave Chamberlain did this recently..but not sure if I saw the write up on procedure..

Good luck...and check the wiring on the connector from the harness first...mine was pretty messed up there too....

Later,
Tom

Thanks guys for the info. I was hoping for some good pics and maybe a write-up, as I don't know diddly about the sensor, it's location, nor very much about electrical troubleshooting. Grog's big hands made for big wrenches, uhh. LOL. It seems like I need an osciliscope and much more knowledge. I'll drop Dave Chamberlain a note and see if he did any documentation on his trials and tribulations that could help. Thanks again my friends. I'll let everyone know what I find, when/if I find the culprit.

:cheers:

Hey Chris,
Thank you for posting about the Hall Sender issue that Wally P helped diagnose with the Bosch Hammer diagnostic unit for both you and me at SITM...and perhaps another few folks up at SITM. Wally wasn't kidding when he said that damned thing is hard to get at either from the top or the bottom of the engine bay. My hands are nowhere the size of "Grog's" but even I have had trouble getting in there...tried to enlist my wife but she politely refused :D

I look forward to hearing what you learn from Dave Chamberlain and to any write-ups or photos or diagrams (however crude). My look through the Porsche PET v5 and WSMs revealed precious little info on the hall sender. Thanks to John Speake, Tom and Bern for the helpful info above.

Where does the ECU-end of the hall sender "wire" get routed into the cabin and to the ECU. I've not yet had to worry about where the ECU is located? Back to the WSMs I go...thanks all!

Tim

Tim,/Chris
The sensor wire goes into the engine bay cableform, and then to the EZK control unit which process the signal. Pin 22 of the EZK. There is a supply voltage to it from pin 5 EZK which I am told is 5v. The 3rd pin of the Hall is a ground return, and also acts as a screen for the signal output from the Hall. The Hall is a semiconductor sensor, not a magnetic pick up inductive type. This is why you need a 'scope to view the signal. Also see the WSM.

It will give out a square wave output pulse as the gap in the disc passes by.

It is run from the camshaft at half engine speed, so that it can determine which knock sensor is giving a signal at a particular point in the engine rotation. From that, it knows which group of 4 cyclinders has the knock.

If the Hall fails, then the ingintion is retarded 6 degrees, as the knock protection system can't work.

The Hall does serve another function. If the flywheel sensor on top of the bell housing fails, then the Hall sensor allows the engine to run in a kind of limp home mode, because it can determine TDC from the camshaft position.

Hope this helps !

Hi John,
Thank you very much for this information...will most certainly be printing out this thread for my archives...
Best regards,
Tim

Ummm... <rubbing sleep from eyes> huh? Where's the snooze button....
Why does my head hurt?
Ok... I'm awake now...

Hey Chris,

No, I didn't do a write-up. At the point where I R&R'd my hall sensor on the '89 I was too obsessed with getting the '89 running. I posted rather the same question you did: "Hall sensor? R&R? Anyone BTDT?" and got zero responses. So, I dove in on my own. I'll have do go under the covers again on the '89 to re-set the cam timing - and I plan to do a write up then.

I was not able to think of any way to get to the sensor without removing the passenger-side (right-side) cam cover. Once you've got the cover removed R&Ring the sensor is obvious. I was, also, not able to figure out a way to get the harness connector disconnected without more room to work in.

I think I posted the basic steps on removing the p-side cover on a cover removal thread a few months ago. Here are the steps as I remember them:

- from underneath disconnect the airpump valve housing from the block (two 13mm bolts and it swings free)
- remove the p-side fuel rail.
- unbolt the guide for the hard fuel line under the p-side fuel rail so that you can move it around enough to get the cover off.
- remove the plugs, breather hoses
- remove the cover bolts - carefully, you don't want to strip them
- you will need to bend slightly the engine lift loop
- a set of stubby racheting allen wrenches is a MUST
- when you remove the cover bolts remove the pressure washers with the bolts - else you may drop them.
- disconnect the LH harness guide from the back (firewall) of the block
- once the cover is loose, lift it up about 1/2", then lift the back of the cover to clear the oil separator, then rotate the back of the cover up, and pull out the cover at an angle.

The sensor is sandwiched between the cam cover and the back-side metal plate on the other side of which is the cam sprocket. You can barely see the little sucker with everything in place. My Neanderthal-proportioned digits didn't allow me to even disconnect the sensor for testing with my scope. So, I just replaced the thing as 1) it was the last possible item that could have been causing my troubles and 2) with my paws it was going to be 90% of the work to test the thing as to replace it.

I'm looking for a picture...

... and don't have a good one. I'm going out to the garage in a little while. I'll see if I can snap one for posting...

Thanks John and David for all the help. It is MUCH appreciated!!!!!!!!!! Any and all pictures will be much appreciated too!!!!!!! Like I said, this is not my forte, so I need all the help I can get.

:cheers:

Here's a picture of the hall sensor connector. It's the brown connector in the middle of the shot.

I have a picture of a damaged Hall sensor from a car, on it's own. But it's too big to post here, Chris. (0.5MegBit)

If you want a copy, mail me at jdsporsche928@aol.com