What is a "cranksenser?"

Allegedly it's a component in a GM starting systems and a common problem. I've never heard of it, but then I only drive cars well.
Tks
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All cars with electronic ignition and fuel injection have a crank sensor. A better name for this is crank position sensor. Usually it is a pick-up that measures changes in a magnetic field as a "gear" moves past the sensor. The teeth on the "gear" provide peaks and valleys that cause a change in the magnetic field at the interface between the sensor and the gear. Usually the "gear" that is used, is not an actual gear in the sense that it mates with another gear to transfer power (although sometimes it is). Usually the gear has one tooth that is positioned differently or that is missing altogether to provide a "zero" reference. A lot of GM cars (and others) have both crank and camshaft position sensors. The crank position sensor provides the computer with information on the location and rotational speed of the crank. The camshaft position sensor allows the computer to know which cylinder is on the compression stroke. This is important for engines that use sequential fuel injection and/or that don't have distributors. GM engines can deduce the compression stroke relationship if the camshaft position sensor fails, but doing so increases the amount of cranking time it takes to start an engine. So, a failed camshaft position sensor usually first manifests itself by longer cranking times. A failed crankshaft position sensor manifest itself by an engine that won't run.
Ed
Stark Raven wrote:

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Is there an easy diagnostic procedure to tell if a CPS has failed other than to replace it which involves pulling the crankshaft pulley.

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On 26 Nov 2003 15:48:27 -0800, snipped-for-privacy@hotmail.com (davefr) wrote:

With a DMM you can check resistance of the sensor to see if it's shorted or open. You can also check the output of the sensor when cranking by looking for an AC (2 wire) or pulsed DC (3 wire) output during cranking.
This however tells you nothing about the quality of the signal. For that you need a scope.
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This may be an answer to my question. I was going to ask if checking and/or replacing the cranksensor is an easy or difficult service procedure. I'm taking my 95 Buick LeSabre,with 35,000 miles, to an independent mechanic who charged $500 for replacing a key cylinder in the steering column, which did not solve the problem. I'm sure he's more than willing to try everything I suggest.
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Stark Raven wrote:

eed a scope.

If he charged you $500 for an unsuccessful steering column repair, perhaps you should consider taking your business elsewhere...
JazzMan
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If I have an engine, 95 Buick LeSabre, 35,000 miles, that intermittently takes anywhere from 6 to 20 cranks to start, but so far has always started and run, I should NOT be looking at the crank position sensor as a possible problem? This failure to run happens in all weathers, on cold or warm engine and in sunshine and rain. It seems totally random.
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I don't follow. Are you saying that you paid someone $500 to replace a key cylinder in hopes of correcting a no-start problem?
What do you mean by cranks? Exactly what is happening?
Steve B.
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Intermittently it may take anywhere from 6 to 20 attempts(cranks) to start my LeSabre. The problem does not show up in an independent mechanic's diagnostic, mostly because when in test, it starts. But a couple of failures to start in testing seemed to point to failed contacts in the key cylinder. Nothing else showed up in test. So the key cylinder was replaced. $500.
The key cylinder was not the problem. The car continues to fail to promptly start. Intermittently. Randomly.
Someone pointed out that the crank sensor may be the problem.
But another comment noted that with a defective crank sensor, the car would simply NOT run.
My concern then was that if with a defective crank position sensor, a motor will not run, the crank sensor is NOT my problem since mine runs well after multiple attempts (cranks) to start it.
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OK. When it does not start is the starter spinning the engine or is the engine silent for the 6 to 20 attempts?
Steve B.
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Yes the starter is turning the engine, as long as the key is engaged; when I release the key the engine does not continue running. Thank God I've got a strong battery; don't know how long that's going to last when I have to crank the engine sometimes 20 times before it finally catches and runs.
May be semantics, but I thought when the car is cranking it was the starter motor turning the engine and the engine was not running until the key was released. But my mechanic says the engine is running when cranking; it just does not continue running when the key is released. I don't know what that means, if anything.
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On 12/26/03 8:34 AM, in article 261220030837223301% snipped-for-privacy@att.net, "Stark

Lots of Hondas in the '90s had this exact problem and it was the ignition switch - the actual electrical switch that is screwed to the back of the key cylinder. For $500 did your mechanic replace the switch, or the lock cylinder?
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wrote:

key
My 92 Honda key cylinder costs about $300. It came with the ignition switch. I bet they don't sell key cylinders alone.
Dear OP: If you thought when the car is cranking it was the starter motor turning the engine and the engine was not running until the key was released then you should do a jump start. Ignition modules tend to be voltage sensitive. Try it: Turn on the high beams, rear defogger, maximum fan, radio etc and see if you can start. Tibur
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Thanks. The motor is definitely turning during the cranking. My limited understanding of auto motors (maybe 20 years old) was that during a start, it was the starter that turned the engine until it caught and ran. My mechanic corrected me saying that during a start, the engine is actually running, but that when the starter key was release, it failed to continue running. 'Fraid the confusion is caused by my limited understanding of automotive matters.
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From reading around it seems your car should've warn you that the crank sensor isn't sending a signal. If it sends wacky signals maybe it won't display a code but it least it should seem like it wants to start. Maybe most logic probe might show a signal from the sensor, maybe not. Anyways, you might just check for fuel and spark. This narrows the field down.
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Thanks. I think my problem is that without codes, there are a dozen elements that could be checked and replaced. Unfortunately, a trial and error approach to this problem could quickly cost more than the value of the car.
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run.
you
You're right, it would cost money to keep troubleshooting. Most places charge $80 per diagnose. I'd would recommend listening for the fuel pump. And then check for spark, but then again, if it's a distriutorless ignition controlled by an on board computer, the spark is too dangerous. If the fuel pump is working and and the injectors are clicking then, the problem is likely between the plugs and the computer. They make spark gap tester about $19, don't know where.
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Unfortunately I am unable to run these checks myself. I would hope that my mechanic performed all of your recommended steps and still found nothing amiss, either via the diagnostic or fuel pump, injectors and spark gap check. And while my LeSabre sat on his lot for 10 days, it started promptly when he chose to work on it.
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snip snip...
for what its worth.... my dad had a 77 chrysler cordoba.... he had problems with it starting as well, although his would either start or it wouldnt... that was randam too... they replaced the on board computer and the problem went away.... this probably wont help, but I d thought I'd chime in...
Fwed
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I've wondered about that too. But my mechanics don't seem too interested. Of course I'm remembering when replacing onboard computers costs around $90. I suspect replacing onboard computers these days cost considerably more.
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