just replaced it after months of erratic behavior culminating in a no start condition , now runs great….but after heavy search..I have yet to fully understand the role of this sensor…..seems to be more important than I thought and the ecu needs good info to work properly (more than retarding timing)


any thoughts???

 

I guess the ecu needs definite info on the position of the cam shafts as I think this is what the hall sensor is keeping track of…. is that correct thinking ?

 

Yup

 

Google Hall Sensor.

 

I believe it is used to determine which of the two candidates fires next. It is needed to avoid wasting one spark and to be able to retard individual cylinders.

(Although now that I think of it it would be possible to retard individual cylinders anyway. Ignition would not know which one is knocking, but it would know that it will be firing again 8 sparks later).

Why the engine does not have a limp home mode when it fails I don't know. Maybe the ignition cannot produce energy for two simultaneous sparks?

 

THe hall sensor identifies cylinder one , the ecu can then calculate where all the other cylinders are .
The engine will run with the speed sensor on the crank , but as the crank rotates twice 720 degrees , the addition of a position sensor on the camshafts , makes it all the more accurate , this ecu then knows which cylinder is firing, or knocking giving the ignition angle, etc with the resolution of the 2 sensors .

 

There's a great book on Bosch EFI and mechanical fuel injection by Charles Probst, published by Bentley Publishing called Bosch Fuel Injection and Engine Management. It's great for understanding the fundamentals of EFI as a separate system, and it's before CAN and all that complicated junk (it's not really, but it can make it confusing for the home mechanic/hobbyist) but still relevant. Plus you can use the knowledge and tests covered in that book on anything else that's fuel injected, as almost every other EFI system in the world is a Bosch licensed system with a few tweaks/changes.

 

I just received a replacement Hall sensor when I crushed the original during my engine installation. Any tricks on getting at it while the engine is in place. It is SUPER tight in there.

 

I used a long extension (8"+) and an Allen driver to get to those lttle bolts. That puts the user end well behind the lifting ear and the FOE harness which otherwise limit the space available for managing the bolts. A wrap of electrical tape holds the bolt to the end of the driver during initial fitment.

The similar 944 sensor will fit perfectly but has a slightly shorter pigtail on it, requiring more careful installation but many fewer dollars cost. Pulling the locking tab/retainer on the connector where it mounts in the bracket allows it to wiggle some in the bracket, enough to let you plug in the sensor with the shorter pigtail on it. Then slide the little retainer back in once the connector is seated.

If/when the cam drive is apart, the rear plate that holds the sensor is pretty easily removable with the sensor still attached. Those little bolts are easy to get to with the plate sitting on the benchtop. Since yours is all apart for the damage recovery, this is an easy option to look at.

And, since there's no such thing as a 928 project without a WYAIT list, the camshaft end seal is relatively easy to renew while all these same parts are off the end of the cam.

 

Nothing associated with the hall sensor will not result in a "no start" condition. Unless your problem is "loom" associated, your problem will be back...

 

Getting those screws out was a b!+ch. I had unfettered access with the engine out of the chassis. I couldn't believe how hard they were to remove. I twisted two allen key sets, used some release agent, and ended up having to hit the screws on the head using a difffent allen key to crack the seal the screw had on the casing. After getting the engine into the bay, I am now looking at how much room I don't have

 

just before I replaced the hall sensor I replaced the crank position sensor too…. may be that is what fixed it ….my computer check on lynx ecu said both were bad, the corrosion was really bad on the hall sensor connector and after clean up I put dielectric grease in there, hope this helps and oh my gosh I hope its not a harness problem….

 

Nothing associated with the hall sensor will not result in a "no start" condition. Unless your problem is "loom" associated, your problem will be back…



now when you say this, Greg , I get a pit in my stomach like a storm coming….ugh!!!

 

What's the story behind that engine in your avatar pic?

I must have overlooked that project - looks interesting.

 

Andy...

Was on my cell phone and didn't see that you were the original poster.

Hall sensor, on your engine, could easily have a "larger role" than on the Bosch injection.

Sorry.