Renix CPS ? No spark

The "All Spark has lost it's spark"! LOL

I have 3 jeeps down all at once now (must a planetary alignment thing), may be riding a bike next,

I need some quick, correct answers, feedback on my new thread so I can narrow this down to the CPS, or Ignition module-Coil, ICM tonight if possible.

I have no spark from the coil, nada, nothing.

I have forgotten a few key details on how to test the feed to the ICM to see if I have a signal to the ICM (and thus the ICM would be bad), and I am trying to recall if the CPS can be tested live while the wires are ("previously cut and soldered by a prior owner" :tears: in a tight space , no room left in the wires) still connected in the harness.....
My 89 Renix has the CPS wires soldered ( no QC) to the harness wires.:banghead:

Has any one ever tested the CPS while connected. I have an analog volt - ohm meter, so I can test unpowered ohms, or ac/dc signals with needle style meter (not digital) but what number do I want to see with it if the CPS is connected to the harness for Ohms??? What is the running CPS voltage peak minimum needed for live cranking test, and was that for an isolated CPS, or one still connected to the ECU - harness tests? I knew all this shit once, just been too long.

I want to look at my options as the two wires are short, no real room to cut and splice extra wire, the way the prior fools did the solder mod.

Also isn't there an ignition wire module input wire I can test, while cranking to see if the CPS signal got to the ECU, and the ECU signal is getting to the ignition module? What is the signal voltage to the ignition module? Is it the yellow wire I would test while cranking? Is it a DC pulse signal that registers as AC? I know the CPS signal wills show up IIRC on AC or DC low volts, 0-1 volt IIRC?

I guess I may need to unsolder the old connections for the CPS to get an ohm test on the CPS.

Thanks!!!!

Just unplug the ECU, test the ohms to the CPS through the connector. Pin/cavity 11 and 28 as I remember it.

ICM:

3-wire connector:

"A"--12 volts from B Latch relay.
"B"--ground, dipstick tube.
"C"--tach signal.

2-wire connector (one wire used):

"B"--ECU square wave input ignition coil input.

Don't forget to check for corrosion on the ICM/coil clips.

Check the B Latch relay and don't forget the the ECU, ICM, o2 sensor and other grounds on the dipstick tube.

Do you need a copy of the CPS mod TSB? If so, PM me your email.

Joe -
I could use a copy of that TSB - please use my addy. I had it before, but I seem to have mislaid it (and I get asked for it every now and again myself...)

Mike -
The coil proper can be tested easily - use an ohmmeter, and you can function-test with a battery. Just do not get your fingers in the spark gap! You can control where the spark goes by using an old spark plug, and just watch that gap instead.

I haven't yet devised a reliable way to test the ICM - probably because I haven't been arsed to build a square wave generator (anyone got a waveform for that taken from an o-scope? I haven't gotten one yet...)

Proper ohms on the HV Coil is?

5-90 said:

Joe -
I could use a copy of that TSB - please use my addy. I had it before, but I seem to have mislaid it (and I get asked for it every now and again myself...)

Mike -
The coil proper can be tested easily - use an ohmmeter, and you can function-test with a battery. Just do not get your fingers in the spark gap! You can control where the spark goes by using an old spark plug, and just watch that gap instead.

I haven't yet devised a reliable way to test the ICM - probably because I haven't been arsed to build a square wave generator (anyone got a waveform for that taken from an o-scope? I haven't gotten one yet...)

Click to expand...

Did you get my PM?

joe_peters said:

Just unplug the ECU, test the ohms to the CPS through the connector. Pin/cavity 11 and 28 as I remember it.

ICM:

3-wire connector:

"A"--12 volts from B Latch relay.
"B"--ground, dipstick tube.
"C"--tach signal.

2-wire connector (one wire used):

"B"--ECU square wave input ignition coil input.

Don't forget to check for corrosion on the ICM/coil clips.

Check the B Latch relay and don't forget the the ECU, ICM, o2 sensor and other grounds on the dipstick tube.

Do you need a copy of the CPS mod TSB? If so, PM me your email.

Click to expand...

Ecomike said:

Proper ohms on the HV Coil is?

Click to expand...

this is totally from memory, and my memory sucks.

Should be somewhere in the 10-15 ohm range.

Dead short is bad
infinite resistance is bad.

maybe....

if no one answers by the time I get home tonight I will look in the FSM for you.

Also, try shorting the CPS wires together, ignition off of course. For some reason this seems to bring them back to life for a little bit, probably clears some sort of magnetic field that's developed. Anyway, short them together, then try starting, if it fires up then my guess would be CPS.

@5-90, I sent you a PM.

My grounds are so good, less than .05 ohms, 5-90 would be envious!

ICM:

3-wire connector:

"A"--12 volts from B Latch relay. I have 12.5 at the battery, and 11.5 V at A

"B"--ground, dipstick tube. .05 ohms

"C"--tach signal. maximum of .180 MV, There but looks VERY weak!

2-wire connector (one wire used):

"B"--ECU square wave input ignition coil input. 4.8 V power on, 5.1 V while cranking, but no signs of wave signal, solid DC it looks like!

Don't forget to check for corrosion on the ICM/coil clips. I had already cleaned and tightened them, Thanks.

Check the B Latch relay and don't forget the the ECU, ICM, o2 sensor and other grounds on the dipstick tube. Grounds all perfect. Fuel pump runs, which I believe confirms B latch relay is working?

joe_peters said:

Just unplug the ECU, test the ohms to the CPS through the connector. Pin/cavity 11 and 28 as I remember it. Getting to the ECU to unplug, and test is almost as much work as replacing the CPS?

ICM:

3-wire connector:

"A"--12 volts from B Latch relay.
"B"--ground, dipstick tube.
"C"--tach signal.

2-wire connector (one wire used):

"B"--ECU square wave input ignition coil input.

Don't forget to check for corrosion on the ICM/coil clips.

Check the B Latch relay and don't forget the the ECU, ICM, o2 sensor and other grounds on the dipstick tube.

Do you need a copy of the CPS mod TSB? If so, PM me your email.

Click to expand...

Well, if you are getting power to "A" on the 3-wire ICM connector then the B Latch relay is working.

Any chance you have a used ICM/coil you could swap in for a quick test?

Just guessing, but the primary side of the coil should have resistance of something like .90-1.5 ohms depending on ambient temps, and the secondary side something like 11,000-13,500 ohms.

I got some more interesting data. harness wire side.

White with a purple stripe was connected to the white CPS sensor lead.

White with black stripe was connected to the Red CPS sensor lead. Not sure the CPS cares?

I checked the sensor with power off, got 295-300 (+/-1) ohms as near as I could tell. Hard to get good solid contact and reading.

Then with power on (but not cranking) I got a voltage across the CPS. I forget, it may have been 5 volts, it was pegging the meter on my low scale, 1 Volt?

I will test the bare harness wires in the morning. I have the sensor unwired from the harness now. I got about 180 MV peak AC out of the isolated (unwired) CPS while cranking. As I recall it should be .6 to .7 volts AC out of the CPS, read with an old style analog volt meter on the 0-1 volt AC setting.

The input voltage I was reading across the sensor (while connected to the harness) while it was in run (ignition key ON, no cranking) has me a little puzzled.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

Shorting the CPS wires for while, they retrying!!!!!!!!!!!!!!!

That sounds interesting!!!!!!!!!!!!!

I may try that and retest the AC voltage while cranking just out of idle curiosity before I yank it.

87manche said:

this is totally from memory, and my memory sucks.

Should be somewhere in the 10-15 ohm range.

Dead short is bad
infinite resistance is bad.

maybe....

if no one answers by the time I get home tonight I will look in the FSM for you.

Also, try shorting the CPS wires together, ignition off of course. For some reason this seems to bring them back to life for a little bit, probably clears some sort of magnetic field that's developed. Anyway, short them together, then try starting, if it fires up then my guess would be CPS.

@5-90, I sent you a PM.

Click to expand...

Older post here:


http://www.naxja.org/forum/showthread.php?t=1012601

Says it should be .5 to .8 volts AC while cranking, and not connected to the wiring harness across the two CPS leads. So mine must be toast!

Also Kastien claims in that thread that the ECU DC voltage across the CPS is 5 volts, so that explains the 5 Volt reading I got across the harness wires.

This looks like another interesting old thread about CPS debugging!

Ecomike said:

My grounds are so good, less than .05 ohms, 5-90 would be envious!

Click to expand...

Envious? Nah - that's on par with mine (I think I run a spec of .005-.01ohm per "step" on grounds - lug-to-chassis, screw-to-lug. Ground run resistance is determined by cable length.)

@87manche - I did get your email, thank you. I just hadn't had a chance to respond yet (this has been a personally very eventful week for me. And nothing fun. Further Deponent Sayeth Not.)

Anyone have any clue what this grommet looks like, where it goes, pictures? It refers to fig 2, but I do not see this "grommet"?

http://autorepair.about.com/library/a/1i/bl534i.htm

Sure you do!

The "grommet" is in place in figure 1, then removed in figure 2.

I don't think the Renix grommet is available anymore. Morris 4x4 has the later HO grommet in stock.

87-90 part numbers:

AUTO TRANS

5300 4909 Qty 1 6 Cyl. Eng., 1987-89
5300 5129 Qty 1 1990

MANUAL TRANS

5300 8017 Qty 1 GROMMET, Sensor

Haven't checked the difference, might just order an HO and see if it will fit or can be modded to fit.

Edited to add manual trans part number.

joe_peters said:

Sure you do!

The "grommet" is in place in figure 1, then removed in figure 2.

I don't think the Renix grommet is available anymore. Morris 4x4 has the later HO grommet in stock.

87-90 part numbers:

5300 4909 Qty 1 6 Cyl. Eng., 1987-89
5300 5129 Qty 1 1990

MANUAL TRANS

5300 8017 Qty 1 GROMMET, Sensor

Haven't checked the difference, might just order an HO and see if it will fit or can be modded to fit.

Click to expand...

These people need to learn English before the write. So the fig 2 is the updated, with no grommet? Why do they call fig 2 the updated version?

Is the grommet even needed?

I think about half of the XJs I have seen are missing that grommet.

It helps when you are changing the crank sensor if you drop a bolt, and probably keeps some gunk out.

I'm not sure about mine.

Here is the 91-01 grommet on Morris 4x4: http://www.jeep4x4center.com/product-information.asp?number=53006010

the grommet is not crucial, it's not like the bellhousing is sealed anyway. Mine has not had a grommet in , lets see, forever.

Turns out the 89 had the grommet. I reused it, as it made it almost impossible to loose a bolt in the bell housing. It turned out to be much easier than I had imagined after reading all the posts in Naxja about the notorious CPS. Not easy, but not near as painful as I expected.

Next task is finding or making the female GM weatherpack connector that is missing from the harness. Then driving the beastie again!

I am thinking it maybe time to stock up those, but where to find the harness side connectors?

Google "GM weather pack connector"