Nice to know stuff

[RAT]

I have been working on my Jeep since the day I purchased it. I have had the transmission out several times and each time the CPS has been removed and reinstalled without issue. Or so I thought. Three or so years ago I started having weird issues with the ignition throwing codes all the time. Usually cylinder # misfire, multiple random misfire. I did all the standard check outs and everything looked fine. Been driving me nuts ever since.
Today I went to the dealer to buy a new torque converter. Seems the one in there now has decided to let go of some of it's internals. While I was there I purchased a new CPS since the price was in line with aftermarket. Come to find out, and the aftermarket parts do not have this, the OEM part has a sticky tape on the end of the CPS that is there to space the CPS the correct distance from the flex plate. When the engine fires up the tape is stripped off and the CPS is happy. I installed an aftermarket CPS three years ago and like I said, it did not mention the gap spacing, and has a slotted hole to make adjustments, but not the tape sticky thingie. Now I would never guess that a magnetic pick up would be that susceptible to this gapping issue but according to the mechanic I spoke to at Don A Vee, it makes all the difference in the world. We will see...

Just a little FYI for my fellow Jeepers...

[USMC 0369]

[COLOR="#800000"]I JUST learned this on Saturday from Rick. We were talking about the CPS being on the harmonic balancer/dampener and he also said the sensor he purchased had a piece of tape on the end of it that stripped off once the engine was started & it was there to gap the sensor from the dampener/balancer.[/COLOR]

[dirtman13]

You guys are lucky. The GM CPS on my 4.3L must go through a "learn process" that requires a special computer. I'd much rather have the ripping tape.

[jonah]

I found out how sensitive to the air gap when I recently added a CPS to my system. I bought an aftermarket sensor that the specs say can operate with up to a 5mm air gap. While I had an oscilloscope at my disposal I tested the CPS at different distances from the trigger wheel, it would still give a signal at 5mm but it was starting to weaken and not be quite as steady. I ended up running it at 1.5 mm and it gave a very consistent signal.

I am sure all sensors have slightly different specs, but it is good to know that it matters and an oscilloscope is handy when messing around with these things.

[aw12345]

Ya wanna run those things as close to the reluctor as you can without damaging them

[USMC 0369]

[COLOR="#800000"]So I guess the question is... does the RAT run any smoother once the CPS is corrected?[/COLOR]

[Jerry Bransford]

Ya wanna run those things as close to the reluctor as you can without damaging them

Not really. There is a sweet spot the reluctance head needs to be at away from the flywheel. I used to have to adjust reluctance head driven computer circuits using an oscilloscope & they definitely should not just be positioned as close as possible... there is definitely a specific distance at which you get the optimal signal shape and output signal voltage. Actually seeing the signal & its shape on an oscilloscope as you move the reluctance head in & out would make a believer out of you.