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Well, actually it will start, but only on about 1% of the attempts I make.
A friend who's much, much smarter about all things mechanical than I has
been helping me troubleshoot this problem for the better part of a week, and
we're mostly stumped.
The problem is a lack of spark. On those rare occasions when we actually
get spark, the car fires right up. And since the spark is plenty strong
when it's there, we've been looking for problem either with the ECU itself
or with one of its inputs. (Yes, we've checked all the connections in the
ignition system, checked the distributor rotor and cap, and so on.)
Near as we can tell, the problem is the signal from the crank reference
sensor (located right next to the RPM sensor on the driver's side of the
block) being too weak. We've tried replacing the sensor, but the signal is
still weaker than my brainy friend thinks it should be. So we rotated the
flywheel until the pin that this sensor is supposed to react to was right
under where the sensor goes, put some putty on the end of the sensor, and
stuck it in its hole to check the clearance. We actually got a bit larger
gap than the .040 that the Bentley manual specifies, but close enough that
it shouldn't be a problem -- say, about .060.
But what we noticed that seemed a bit odd was this: The indentation from
the pin in the putty only went about halfway across the "business" end of
the sensor. It would seem to me that in order to generate a decent signal,
this pin should extend all the way across the sensor's surface as it whizzes
by. There really isn't any wiggle room in which to adjust the sensor so as
to move it closer to the flywheel and therefore get a better reaction from
this pin, so either our observation (about the pin only coming halfway
across the bottom of the sensor) is normal, or there's something wrong with
the pin. We didn't see anything in the Bentley manual about this particular
detail (doesn't mean it's not in there somewhere), so I'm hoping that
somebody here can help out. FWIW, the starter was replaced (by a mechanic)
just prior to this problem cropping up, so it's not completely impossible
that this pin was somehow damaged in the process.
Can any of the gearheads here confirm whether our observed alignment of the
pin with the crank reference sensor is normal or not, so we can either
pursue fixing it or move on to something else? (And we're pretty much
completely out of "something else's" at this point.) And does anybody have
any other ideas as to what might be the problem?
Many thanks in advance!!
1976 Cadillac Fleetwood 9-passenger sedan
(for sale: http://www.dataspire.com/caddy )
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