[Diy_efi] northstar DIS and what it all means ?

[John Stricker]

I can't tell you what the engine will do on the fuel side in the event of=
 a
cam sensor failure, but I'm trying to figure it out on the trouble shooti=
ng
charts.  The cam sensor is used to provide the ICM with cylinder #1 firin=
g
order information to control the SFI.

As for the dual crank sensors, the crankshaft has a reluctor ring with 24
evenly spaced notches plus eight additional notches used for synch.  The =
two
sensors are spaced so that the signal of the lower one lags the upper by =
27=B0
of rotation.  The ICM first counts the number of the lower pulses between
every two upper pulses.  There can be 0,1, or 2 lower pulses between uppe=
r
pulses.  When the ICM sees 0 lower pulses between upper pulses, it starts
counting lower pulses between upper pulses.  when it counts exactly 4, it
synchs the ignition on the very next upper pulse.  If the ICM counts over=
 4,
it waits for another '0' lower pulse between upper pulses to start counti=
ng
again.  This allows the ignition to synch and fire the fist spark plug
within 180=B0 of engine revolution.

I suspect the engine will continue to run in a limp home mode, although I=
'm
not sure, because the purpose of the dual sensors is to provide quick syn=
ch
and starting and to allow the ICM to maintain ignition synch even if one =
of
the three sensors is bad.

If it will help you, I can email the ICM input and output pulse chart to
you.

Hope this helps.

John Stricker.
----- Original Message -----
From: <Djfreggens at aol.com>
To: <diy-efi at diy-efi.org>
Sent: Monday, December 30, 2002 5:32 PM
Subject: [Diy_efi] northstar DIS and what it all means ?


> i got my hand today on a northstar v8 dis ecm sehcmatic. i was looking =
at
it
> and wondering if the dis doenst see a signal for the cam what does it d=
o
??
> would it go into a limp home mode and fix timing or would it simply go
into a
> batch fire mode. also it has 2 crank pickups what for. btw this is for =
a
94
> system. ive been reasearching this for use with a 727 and $8f code. its
looks
> like a good system to pirate if itll work. i would imagine that gm kept
the
> dweel control strategy. but as for the 24x siganl. what would you send =
the
> ecm the 24x or the 4x and if you disabled the cam would the signal for =
24x
> revert 6x ?? im hoping somebody out there has some answers. guidance an=
d
help
> apprciated.
>


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