CKS Fun

Hypoid said:

Prove that the old part failed in the expected operating conditions. My education is far inferior to yours, there is much that I do not know. I do know that you have condemned a part on visual examination. Where are the numbers? Where is the process of deduction based on measurements? Some of us under educated folk thrive on such a framework.

How can an inductive pickup distort the thermoplastic that supports it?

Back to the running like a turd question; did you dump the memory in the ECU?

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As mentioned earlier in the thread, it reads fine cold or when cooled off after a heat soak event, so quickly in fact that I've never been able to get a bad DVOM reading of the 158k melt piece.

These things are nothing more than a freakin’ permanent magnet that is wound with wires. When it gets excited by a passing chunk of metal it induces current in the windings surrounding it, an on/off sort of switch if you will that the stupid engine management system reads.
The only purpose these serve in our rigs is to kill fuel and juice if you shove a piston/rod out the side of the block in an effort to prevent fires and lawsuits. Obviously the crank breaks or stops spinning at that point anyway . . . most of the time.
Well hellza, I know when that happens, having experienced it before a few times . . . can’t miss it, makes one heck of a racket!! Just turn off the dang engine via the ignition switch.
The very fact that it isn’t written into OBD I or OBD II firmware to throw codes is enlightening.
I’m thinking mine is actually too close and is reading the recesses as well as the rises, once rpm increases it doesn’t know WTF to do as it's all read "on" and not on/off/on!
Yes, I dumped the OBD I crud what little there is of it. I own and work on modern OBD II rigs of mine when ever required, ain't scared and have never failed to repair one. :heart:

FourCJsOneXJ said:

These things are nothing more than a freakin’ permanent magnet that is wound with wires. When it gets excited by a passing chunk of metal it induces current in the windings surrounding it, an on/off sort of switch if you will that the stupid engine management system reads.

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Right so far

FourCJsOneXJ said:

The only purpose these serve in our rigs is to kill fuel and juice if you shove a piston/rod out the side of the block in an effort to prevent fires and lawsuits. Obviously the crank breaks or stops spinning at that point anyway . . . most of the time.

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FourCJsOneXJ said:

Well hellza, I know when that happens, having experienced it before a few times . . . can’t miss it, makes one heck of a racket!! Just turn off the dang engine via the ignition switch.

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Not right at all -- the sensor tells the PCM the rotational position of the crankshaft so it can trigger the injectors and the spark at the proper times. The PCM also uses the camshaft position sensor to determine whether a particular cylinder is coming to TDC on compression (spark needed soon) or exhaust.

The PCM also looks at the rate of change of the interval between pulses to determine the degree of acceleration (positive or negative).

The crankshaft and camshaft position sensors are crucial to the proper operation of the engine.

FourCJsOneXJ said:

The very fact that it isn’t written into OBD I or OBD II firmware to throw codes is enlightening.

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FourCJsOneXJ said:

I’m thinking mine is actually too close and is reading the recesses as well as the rises, once rpm increases it doesn’t know WTF to do as it's all read "on" and not on/off/on!
Yes, I dumped the OBD I crud what little there is of it. I own and work on modern OBD II rigs of mine when ever required, ain't scared and have never failed to repair one. :heart:

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Instead of making assumptions why not make some measurements? Get a scope (oscilloscope) and watch the signal from the sensor and you will SEE if it is pegged one way or the other, or if you are getting the nice waveform you should be getting.

Pocket oscilloscopes are cheap and very useful. You don't need lab grade -- there are some in the $60-class that can be quite useful for debugging all kinds of stuff, including mysterious engine problems.

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I'm sorry about the messy quotes but this site keeps "correcting" my attempts to properly quote multiple paragraphs into the mess you see.

It's fixed and was too close but your are right, that "dumb" sensor does even more than what you listed. I got a good education on the role it plays and will share the links as soon as I can get them together.

FourCJsOneXJ said:

It's fixed and was too close but your are right, that "dumb" sensor does even more than what you listed. I got a good education on the role it plays and will share the links as soon as I can get them together.

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Alright, as stated above the sensor head was in fact too close but it was not molested.

The bell housing bolts were all still properly torqued, the dowels still intact, where they should be and there were no signs of any drop, shifting or movement what-so-ever.

As mentioned earlier, mine has the non-adjustable sensor. It still has the factory shoulder bolts too and though I slotted the old and new sensors for ease of swapping without taking the bolts out, the seated position remains the same.

I ordered a new OEM Mopar badged and bagged replacement sensor that carries the same part number as the melted piece removed, 56026921.

Knowing that some sensors come with a sacrificial paper spacer I A$$-U-MEd those were the adjustable type and that mine, being non-adjustable, would just home on the shoulder bolts with a proper air gap. When the replacement arrived and did NOT have the paper, I thought nothing of it . . . WRONG!!

A part number for one of those little paper sacrificial air gap spacer jewels is 05252229, it’s round and here’s a picture. There may be other part numbers for the sensors like my rectangular one. It sets up an air gap of about .031 according to documentation I found, approximately the amount of slop in the holes of my non-modified fixed sensors with factory shoulder bolts inserted prior to slotting them.

Everything I've read says to shove the senor down as far the shoulder bolts will allow, I have to A$$-U-ME those instruction are for sensors equipped with the paper spacer.

I dug around in the garage for some stiff corrugated cardboard (not solid) with the proper thickness which is about the same as two chunks of cereal box cardboard. Finally found one, trimmed it to fit the sensor head and glued it on.

Reinstalled the sensor applying slight downward pressure so as not to crush the cardboard and tighten it up. Crossed my fingers, fired it up, let it come up to temp and the thing now revs out the back door just like it did before the initial sensor swap.

A quick heat soak test in many of the places near my home where it would consistently make the rig act up have thus far proven it was in fact a thermal issue with the sensor. Further extensive testing will be done today when I can get the thing on a long flat straight stretch of road around here which are almost non-existent. I've had enough of that "dies at 55mph on a narrow road filled with blind curves and no shoulder" stuff!!

I have no idea what caused the mushroomed melt down of the suspect failed piece. It may be a replacement that was done before I got the rig that was installed without the air gap and managed to run long enough to self clearance. It's hard to imagine given the way mine ran with no air gap but who knows? There are no exhaust leaks or other sources of significant heat near it though there could have been before I got it.

Knowing my three OBDII rigs well, I never thought this OBDI rig was as complex as it is (only one OBDI I've owned) but got this rude education. I figured the purpose of that sensor was as simple as it is . . . WRONG!!!

Here are some links I found useful . . .

A humorous informative troubleshooting dissection covering common problems.


An index of various systems tests including the CKP Test.