[urq] Starting issues... Hall Sender?

[urq]

... beg to differ ... 

What you are describing at the beginning are the variable reluctance sensors
... the "speed" and "reference" sensors which sense the teeth and reference
pin on the flywheel ... but the description is correct.  Measuring the
resistance of the sender does have some value, but these sensors can also
show some temperature dependent failure.  The PT engine on the V8 uses a
very similar scheme, with the exception that the sensors are mounted rather
close to the exhaust system and are a common cause of difficult starting
when hot, or engine stalling.  The WX does not seem to suffer this symptom
as much IME.  

A Hall Sensor is a bit fancier a piece ... it is actually a semiconductor
device that senses the presence/absence of a magnetic field and switches on
and off based on the field.  This part has three terminals, power, ground
and the switched signal.  I don't know if an ohmmeter really will help tell
anything more than perhaps if the wires to the sender are broken.  Here
again, the part used on the WX seems to be more robust than that on the V8
engine ... but on the V8 the engine will still run when the Hall sender
fails ...

Steve B
San José, CA (USA)

-----Original Message-----

Hall sensors are simple coil on magnet design and you can check any of 
them simply for continuity, and no contact with the body. Weak signal is 
usually ferrous debris on the magnets, or distance between the pin and 
the sensor. If the sensor is stuck, its not the oxide fusion problem, 
because the sensor body is SS and top is plastic, so gentle shock and 
some lube will do, but you shouldn't twist it, but pry it out 
vertically, starting with a thin knife and more lube and it will come 
out. Naturally, check if is OK first and check the plug contacts for 
corrosion. Symptom of working before but not after stationary period 
suggest the corrosion, so check all three sensor plugs first.
SS and RMS sensor you can energize by flicking screwdriver over its 
magnets, which should give you a measurable signal, although the 
continuity test tells the story first. Distributor same, position it 
when the window is just to enter the hall coil, mark the position, 
loosen the clamp and flick it around. That should give you measurable 
signal. Of course, return to mark and tighten.

HTH, Ado


> The starting problem returns!
>
>I was just starting to work on some extra goodies on Gobi this  
>weekend (early morning) when I was getting ready to run her up some  
>ramps... she wouldn't start. Okay, been through this process before,  
>right! Did all the usual "car does not start" diagnostics and the  
>only thing I came up with when I was using my homemade LED test light  
>at the ECU, was when I cranked the engine while testing the Hall  
>Sender, the light stayed on constant, not flickering like the manual  
>stated. Then I checked the Reference Mark Sensor (with LED) and  
>thought the pulsing signal was a very weak. I have since replaced the  
>Speed Sensor with the same symptom (weak signal) and she fired right up.
>
>Okay, now that you know the background. Here's what I must ask. If  
>the test light for the Hall Sender doesn't flicker, does that mean  
>it's faulty and needs to be replace (not sure how to do this yet) or,  
>is it a faulty Reference Mark Sensor? If it's the RMS, I can't budge  
>the damn thing! I think the aluminum sleeve has fused with the tranny.
>
>Any advice on this? I need to get her back on the road for the next  
>event in two weeks.
>
>
>  
>


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