[urq] 84 urq sensor and ign module testing

[Buchholz, Steven]

... it's a bummer to hear that you're paying money for stuff that isn't
guaranteed to be the problem!

If you can't get the car to someone who knows anything about Audi
ignition control systems, at least have them read the Audi maintenance
docs ... martin has them on his site, here's a link to the maintenance
and adjustments doc ...

	http://www.quattro.ca/Urq/urq-IST-MaintAdj.pdf

The signal from the speed and timing sensors is an analog pulse that
swings positive and negative as the item being sensed passes the sensor.
On the reference signal you will see a distinct positive and negative
pulses because there is one pin, but on the speed sensor the signal
looks somewhat like a sine wave.  You will only see a signal when the
flywheel is turning as the sensors are generating a voltage based on a
moving magnetic field ... no motion, no signal ... 

Far and away the most common situation is that the Hall Sender signal on
the distributor gets out of sync with the flywheel pins ... usually due
to a shifting of the cam vs. crank timing due to the belt slipping.  Set
the engine to TDC on the crank and make sure the distributor rotor is
pointing at the reference mark on the distributor housing (you may have
to crank the engine to TDC twice to find the proper point.  

Be sure to read over the troubleshooting section of the document above,
and pass along the info to the folks working on your car.  I heartily
recommend to anyone who chooses to own an urq to learn for yourself the
way the ignition/fuel system works ... there are precious few mechanics
who have a need to know this level of detail ... 

Steve B
San Jose, CA (USA)
> 
> Replaced sensor {Crank or Rpm} under distributor still
> no fire. Does anyone have the specs on what the sensor
> should read to make sure its operating right? Also the
> specs on the ignition module, and a testing procedure
> for this also? The shop can't find anything regarding
> these for my car{84 urq}.