CPS Resistance - Which TSRM do I follow????????

[ForcedTorque]

I am having a problem getting my car to start, so I am testing parts all over my car with my 1992 TSRM. My car is a 1992, but I have no idea of the origin of the motor. I bought it as a rebuilt JDM, that I was told came out of a soarer of unknown year. It does have a grey plugged CPS.

I generally look up what I want on the cygnus site, and get a page number to use in my handheld TSRM. I did that to test my CPS, and my results were not within the 185-265 specs that my book has. I came back into the computer, and the Cygnus was still on my screen, and it had the values at 140-180. So, my 161-165 results fall within spec on the CYGNUS. I thought that Cygnus was done on a 1991 format, which would also use a grey plugged CPS, and should show the same values.

I'm lost as to whether I'm in spec, and should keep looking - Or, am I out of spec, and have found my problem???????

 

[toyotanos]

You are right that the specs changed from year to year. It also depends on how warm the coils are; it changes the reading. Super cold=lower, hot=higher resistance (I would aim for 60-85 degrees F) The 87 tsrm I have says 140-180 ohms, and my 91 TSRM says 205-255, so I would suspect you have an earlier engine/CPS.

The best thing I could think of would be to try another (correct year) CPS, but that's not always easy. I could see this being an issue with a gray plug computer. You may want to check your air gaps- they may be too wide as well. Another thing I have experienced directly would be the Cold-start injector circuit not working- cranks for 5 secs, re-try and it fires up.

Edit: no temp spec is given so I would assume cold engine, not op. temp. *Please correct me if I'm wrong*

 

[kotu100]

You probably looked, but i checked the 1987 also and that says 140-180 as well.
I've run both green and grey plug CPS' in my car with no problems.


*edit: i ninja'd by toyotanos

 

[Poodles]

It's fine, the airgap is more important...

 

[ForcedTorque]

I'm going to have to go get a feeler gauge to proceed then. How would the air gap change over the years? The fact that it is a gap should eliminate the possibility of any friction, right?

 

[toyotanos]

No- the airgap is necessary so that the teeth on the shaft don't hit the coils and destroy themselves. The tighter the gap, the stronger the signal will be, but you need to leave space for thermal expansion. It's not common for the gap to change, but it's something that's worth checking, since you're having problems.

 

[IJ.]

Voltage goes way up the tighter the airgap is to a point.

Ok in a new tight CPS but in one with a bit of wear you run the risk of it scraping a post.

 

[ForcedTorque]

OK, I now own a feeler gauge.

Both the G1 and G2 are .010in, so they are within spec.

Now, if I am understanding the TSRM correctly, I test the NE between the top of the gear teeth to the pick up. I'm not sure how to even get a feeler there. But, I can see with the eye that the gap there is much different. It looks to be a gap of about an 1/8" or somewhere thereabout.

 

[IJ.]

10 thou = house brick

I usually close them down to 2 if the CPS is tight, I bought a brand new one that wouldn't run using the factory adjustment as received, the MoTeC has a test feature you can run on cranking, spoke with my MoTeC guy and he suggested the 2 thou setting, bingo big fat signal and started right away.

 

[toyotanos]

Holy crap Ian! You ran that sucker tight!

As for the NE signal, it's super loose if it's even close to 1/8" (125 thou, specs are .008-.016). Also, since you are running a lower resistance pickup coil, it will produce less voltage with the same gap as compared to the original.
Tighten up the gaps, especially that NE one. It's the crank sensor signal, so losing it would definately cause a hard start!

 

[ForcedTorque]

I don't see any instructions on how to tighten or adjust the sensors. Any tips would be greatly appreciated. I guess I will be pulling the thing out tomorrow to work on it. I'm using a flashlight just to see in there where the car is parked.

 

[IJ.]

Ever adjusted a set of points??

 

[ForcedTorque]

Leave it to the Chevy guy to bring up points!

Like I said, I was working by a very dim flashlight, and very little daylight coming into my carport (blocked by the open hood). I didn't remember seeing any adjustment screws, and the TSRM saying to replace if out of spec gave me doubts that there were any. I will get a better idea what I'm playing with tomorrow.

 

[IJ.]

LOL I was being serious the adjustment is exactly like a set of points

 

[jetjock]

He's right. Just like points. That's what the little cut out is for. That said you're asking for trouble...

 

[ForcedTorque]

That said you're asking for trouble...

Care to expand on that some?

 

[jetjock]

The only way to optimally set them is with a scope and if you had one you'd already know if your problem was CPS related. And fwiw a weak signal can't effect how the engine starts by varying degrees. It's either strong enough to bias the ECU's A/D converter or it isn't. Not to mention a signal that falls below the minimum required (1 volt p/p @ 300 rpm) will result in a code being set. Instead of messing with something the factory explicitly states not to why don't you simply check spark? If the ignition system generates it at cranking speed the CPS is working...

 

[ForcedTorque]

Thank you for that explanation!

I got hung up here at the CPS because of the differing TSRM specs. I know that I am at least getting some spark, as it will start occasionally, but won't stay running when it does. I'm guessing that maybe I have a bad coil or two, or my problem could be something other than the CPS. I will keep on my track of testing. If I can't find any other suspects, I will come back to the CPS later, after ruling everything else out. Then, I will make an attempt to repair, before buying another CPS.

 

[Doward]

Go to Autozone and buy the OEM brand spark-plug tester. If you have spark (even weak spark) your engine WILL run on it.