[urq] "Doesn't Need Distributor Signal"

[craigcook at rogers.com]

Hi Steve,

reading between the lines, I guess you could say if the hall sender was shorting
to ground then the engine wouldn't run, or if it was intermittently shorting to ground, then
it could create a driveability issue. Sounds good to me.

I recently had a 85 urq in for a no start. It turned out to be the hall sender in the
distributor. 

I had a 5 window distributor laying around and thought I'd give it a try.

I re-indexed the distributor to compensate for the hall sender being in a different
position on the distributor body. The car started and ran fine with the 5 window.

The customer is still driving it to this day.

I guess once the computer see's the correct timing event it doesn't bother to check
the correlation again.

Just a bit off info in case you have a no start due to a bad distributor , and have a 5 window distributor laying around.


Cheers,

Craig Cook


--- On Thu, 3/25/10, urq <urq at pacbell.net> wrote:

From: urq <urq at pacbell.net>
Subject: Re: [urq] "Doesn't Need Distributor Signal"
To: quattro at audifans.com, urq at audifans.com
Cc: "'S-CAR list'" <s-car-list at audifans.com>
Date: Thursday, March 25, 2010, 11:08 AM

Craig wrote:

 


Good point, however the urq doesn't need the distributor signal after start
up.


 

. and you say this because you know that you can pull the cable off the Hall
Sender while the engine is running (on an urq, 5kT, v8q, ???) and the engine
doesn't stop running, correct?  Yes, I have done that test too, and have
been tending to agree . 

 

. but it is also well known that should the distributor timing get too far
out relative to the crankshaft the engine will cut out and die . in fact
this was one of my first findings when I got my urq way back when.  Ned
Ritchie printed this info in a QQ issue when I asked about a 4k RPM cut out
I had many, many years ago . 

 

Both these statements can't be true . and I now realize what is missing in
the first statement.  The Hall Sender has two states, and in some ways you
can think of it just like a set of points in an older car.  When you remove
the connector from the Hall Sender it is as though the "points" are open all
the time, and I agree that in this condition the engine will continue to run
(I too have run this experiment).  The thing is, if you then simulated the
points being closed by grounding the Hall sender signal to the ECU the
engine will stop running.  I have not yet run this experiment, but since I
know the circuitry on the ECU gates the reference pin signal with the Hall
Sender signal, the "closed points" will stop the reference mark signal .
this also explains the second fact.  If the crank to cam timing gets to the
point where the Hall Window no longer matches up with the reference pulse,
the "closed points" prevent the reference pulse from getting to the
computer.  

 

This mechanism was intended to ensure the ignition was synched to the proper
TDC mark (which is more important on an engine with an odd number of
cylinders), but it also provides some protection in cases where the timing
belt jumps teeth.  Of course it won't help much if the timing belt breaks . 

 

Steve Buchholz

 

 

_______________________________________________
Audifans urq mailing list
Manage your list connection: http://www.audifans.com/mailman/listinfo/urq
http://www.audifans.com/kb/List_information

Pictures/Polls/Database at: http://autos.groups.yahoo.com/group/urquattro/