Crank trigger signal, runout, refrigerator magnets in the wheel?

[Bob Wooten]

When I was looking into them (hall sensors, that is) I seemed to recall that
some of them will not work @ low rpm.  the selling point for some of them
(Allegro or something like that) was that they would work from 100 rpm up to
some number & some of them did not have a minimum spec that made me think
that they were bad & they did not want to advertise that.  makes me think
that you might not be able to see a signal (or a reliable one).  have you
looked @ it before during crank mode?  if so, don't give this another
thought, something to consider though.

BW

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of clayb at sonic.net
Sent: Saturday, May 05, 2001 10:44 PM
To: diy_efi at diy-efi.org
Subject: Crank trigger signal, runout, refrigerator magnets in the
wheel?


Hi guys,

I think I'm having trouble with the signal reliability from my Crane
Cams crank trigger.

The trigger wheel is Crane Cams Hall effect. I hooked up the scope.
Unless the
scope is glitching at 12 Hz (150 RPM cranking speed), that crank trigger
is glitching. I've had this Autronics/Crane trigger setup working in the
past, but it has proved very proximity sensitive. The trigger wheel
wants to be rubbing against the Hall pickup, perfectly centered, with
.000" runout.  but after I installed a new engine (same balancer and
trigger arrangement) the trigger became intermittent, again! I've had
the new engine running also, of course. But it went intermittent again
100 yards from shore. Grrrr...
The plugs stopped sparking, but there was still fuel going
through the injectors, according to my nose.

According to the scope, the cam pos sensor is fine.

I believe, based on past experience with this stupid trigger, the "43"
code
thrown by the computer, the traces on the O-scope, and the lack of
ignition firing, that I may have a problem with magnetic field strength,
runout, Hall sensor sensitivity, etc. I measured the wheel
runout at .040". What do they expect out of a wheel centered by the
three pulley bolts?
Sure, the wheel isn't perfectly in line with the center of the Hall
sensor, but the center of the sensor is still "covered" by the wheel.
I'm starting to think this setup just ain't gonna cut it. I'm
going to make some phone calls, and check the magnet strength, but I
strongly suspect the Crane is ill designed and has weak magnets,
creating an unreasonable proximity requirement.

http://www.cranecams.com/ignition1/ctrigger.htm

MSD mentions rare earth magnets. I think the Crane trigger wheel magnets
are ex-refrigerator units!
http://www.msdignition.com/1msdcrnk.htm

Has anyone had experiences with this particular brand of crank trigger,
or suggestions on how to fix what I have? I'm hoping the Hall sensor
itself is OK, as it is already mounted with bracket and adjuster. (It
does, by the way, respond to a medium Gauss magnet placed against it.)

- Clay
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