Question : 3100 DIS issues

[Maverick H1L]

I've got a question about the DIS on the 3100.

If I have both plug wires off of the same coil, should a spark not jump between the wire terminals when cranking? Mine doesn't. And yes, it's got power and ground.

Also, what VAC reading should I be getting at the module end of the 7x CKP wire while cranking? It doesn't seem to me that I'm getting very much. From what I've read, the 7x is supposed to be pretty close to the reluctor ring. My TCE kit has the metal tip of the 7x about a half inch away from the notches, and that's with the bracket pushed as close to the damper as possible (it was bad enough I had to put washers in behind the bracket to get it lined up with the notches and yes, I do have the damper on all the way).

:edit: According to the pic on the britishcarconversions.com site, it looks like my standard 3100 7x CKP is too short? Pic attached below is from the site. I don't have one of mine, but the tip of the CKP is well inside the tube on the bracket.

[ericjon262]

a 3100 should have an internal ring, with no requirement for an external one. my understanding is that the gap between the sensor and the ring should be .050"

[caffeine]

I think he's using a RWD block ericjon. But ya, sounds like the crank sensor is nowhere near close enough to the reluctor ring. Maybe try a 3.1L sensor?

[Maverick H1L]

caffeine would be correct... I'm running 3100 heads on a 3.1 RWD block. No provision for the internal 7x. The crank doesn't even have the tone ring.

Are the 3x00, 2.8/3.1/3.4 7x CKP sensors not the same? It seems to me that they would be since they all mount the same in the same place on the block, but maybe that's just me?

[caffeine]

Ya according to rock auto they're all interchangeable... Maybe something's wrong with the bracket? Or you somehow ended up with the wrong sensor?

[Maverick H1L]

Ya according to rock auto they're all interchangeable... Maybe something's wrong with the bracket? Or you somehow ended up with the wrong sensor?

Well, I looked up the P/N on rock auto an the info says it's for cars between 1987 and 2000. Specifically, Luminas between 1990 and 2001. It's a Standard PC7. However, when I look up for, say, a 1994 Camaro, it shows a PC28. I suppose I need to buy another one. Doh!

The worst part? The sensor is about an inch longer. So where does the other $30 in price come from?

[caffeine]

Weird I never would have guessed RWD used a different sensor

[Maverick H1L]

I don't get it, either. Makes no sense to me. Maybe it's located in a different place because of the starter mounting being right where the other 7x sensor would mount. I also don't get how an extra inch or whatever in length warrants a $30 price jump (I paid less than 10 for mine and the cheapest one I've seen is $35 plus shipping and what not).

I guess I'll get another 7x. Anyone need one for a FWD car?

Just need to make sure that I should see a spark jump between the 2 towers of a single coil when I get everything together...

[caffeine]

Could just ground one post and hook up a spark tester to the other

[Purple pit]

I thought the 7x was in the block and the 24x was the crank.

[Maverick H1L]

I thought the 7x was in the block and the 24x was the crank.

There are 2 CKP sensors, the 7x and the 24x. The 7x uses notches cut in the center of the crank to send a signal to the ignition module for a rough position of the crank, for starting and as a backup in case the 24x fails. The 24x goes straight to the ECM for fine tuning of the ignition timing and fuel injection pulses, and uses a wheel on the back of the damper.

I have an RWD engine that doesn't have a block provision OR the crank notches for the 7x, so I had to buy an external trigger kit to use the 3100 DIS. The damper in the kit has both the crank notches (in the outer ring) and the 24x trigger on the back (as in the 3.4 RWD).

[Purple pit]

Ok thanks, I didn't know much about the RWD sensors.

[Maverick H1L]

It's the same as yours, just different parts. If you remove the damper, you will see a pressed metal ring with teeth on the back, with the teeth pointed towards the engine. There is a 24x sensor somewhere on the timing cover that the teeth pass through to generate the signal. This is similar to the dual rings utilized on the 3800 engines (actually, I think that may be where the idea came from since the Fast Start system may have been developed first).

[Purple pit]

Yeah I took a good long look at the 24x not that long ago. I felt a need to change it do to a idle problem. Not knowing at the time that you had to put off the damper. The real problem is an upper intake leak and a vacuum leak.
Thank you for the info!

[Maverick H1L]

Got the RWD 3.4 sensor yesterday. I compared it to the FWD sensor a little while ago and it indeed is about 1/2" longer. I need to let the battery charge overnight (I'll be replacing it soon enough... other things come first) before I can check for spark again.

Also, does the DIS require an ECM to be hooked up to fire off? My MSII isn't in the car yet (need to work on the case).