[urq] reference sensor bench testing

[Mike Del Tergo]

Steve,

In the IST (check list for no start) the speed ref sensor test comes first and as I mentioned that tested OK.  (via LED test)  I'll see if I can also get my hands on an ocilliscope.  Later sensors (at least MC) are a no go as they are too short and have a larger diameter that will no allow insertion into the WR block.


From: "urq" urq at pacbell.net

 
If I recall correctly you are using the procedure described in the IST - M&A
document, right? This would mean that you are using some sort of LED tester
and cranking the engine, correct? I have not tried this myself, but I have
observed the reference and speed signals on an oscilloscope. While I
definitely prefer a dynamic test such as this to the resistance based test
in the Bentley, I would still urge caution. The amount of voltage generated
by the reference pin is going to be dependent on the cranking speed, make
sure the battery is fully charged and the cranking speed is not too slow.
The flash will also occur once per revolution of the engine. It would also
be better to run this test in a dark area. I would recommend that you test
using the speed sensor first to see how bright the LED gets.
 
I don't remember the exact details of the problem you are experiencing, but
since you are still suspecting the speed sensor you may want to test with a
similar unit from a newer car (not a V8Q though! :) See if your symptoms
change. You could verify using the bench test you are now doing, but I'd
recommend that you try running the engine for a while with a different
reference sensor installed.
 
Steve Buchholz

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