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I have an issue with a hall effect trigger.
The engine is a bit of a hybrid... it's a chev LT1, the optispark has been removed and a vortec distributor fitted. it's running an 808 and I am using OSE.
This is where the problem lies.. After weeks of fault finding and being assured that the dissy had been checked and having found fuel pressure, cam timing, lifter preload, etc problems, I found the rotor phasing was way out. Sorted out the phasing and I thought, problem solved.
No chance.. With the ignition on and the engine not running, rotating the distributor would result in the ecu cutting out, multiple ignition triggers whilst stationary or an actual trigger. I have never seen this problem before.
I was always suspicious that this dissy was causing a host of running issues so I pulled it out and looked into how to check the operation of the hall effect sensor.
Setting it up on the bench and checking the output with a meter between the output and ground, I found that when the sensor was open, I had no voltage and 357 ohms. Closed it has 13.68v and no continuity. Seemed strange to me so I checked a holden hall effect sensor. Open it had 0v and 17.2 ohms and closed it was at 0.28v with no continuity.
It appears to me that the vortec module is switching +Ve and the holden is switching the earth?
Changing the sensor to the holden type will be a major headache due to the design of the dissy ( and the fact that is in a show winning car, it needs to be neat..)
Is there a way, maybe using a transistor or the like to switch the output around in a simple way?

I think your logic sounds correct. Delcos generally do switch the ground. And yes Im sure there is some kind of a simple circuit to implement such a fix, though I dont know what it is off the top of my head.

http://www.ebay.com/itm/87-95-chevy-gm- ... 0862873800 might fix the issues

Thanks for the reply.

I looked into changing the dissy, but it isn't an option. The vortec is a 'crab cap' style that fits under the dress covers and it would need to be modified as the LT1 conversion ( because it was not done correctly) requires the dissy to be shortened.

The Holden hall pulls the signal low when the trigger tooth is not in the sensor air gap, bench testing it without the ign module needs a pullup resistor from the signal line to 12V to get an output voltage when the tooth is within the sensor.

So the Vortec dizzy sounds similar?

The holden V8 module is expecting the signal from the dizzy to go low at the defined ref angle (60deg standard) and high around 10 deg to fire the plug while cranking. The signal also goes to the ECU as the ref pulse. The vortec dizzy trigger disc needs to be similar to allow for the ref angle, cranking dwell and plug firing.

Lawso wrote: With the ignition on and the engine not running, rotating the distributor would result in the ecu cutting out, multiple ignition triggers whilst stationary or an actual trigger.

Is it possible that the trigger wire and the +12v wire to the sensor are swapped? That would cause the +12V from the ECU to the sensor to get momentarily shorted when you rotate the distributor, and that could cause all sorts of odd behaviour.

Thanks again for the replies.

The vortec dissy in it's original form is setup as a 1x cam position sensor only. May explain the weirdness..
The dissy was modified by someone in the past and was fitted with an 8x shutter wheel.

I have bit the bullet though and retrofitted another hall effect sensor. Jaycar sell a nice little unit for $20.
The jaycar unit tests the same as the holden sensor so I'm crossing my fingers that it will work this time..

Installed the modified dissy. All is now as it should be and is working normally.

Cool. Got any pics of how it ended up? sounds like a good solution.

Might be a while before I get back to the car as it's going in for a face lift (typical show cars...) But I will get some pics of the setup.

But, here's a pic of the car. The bonnet, etc are off as I was working on it.