Renix heads help request!

I need a favor. I am trying to decide if I should use the "if it ain't broke don't fix it" theorem, or if both my Running Renix jeeps are likely to give me CPS no start, died on the road trouble again any day now. I have a detailed thread with detailed CPS to ICM voltage test data on my 89 and 87 Renix Jeeps, here:

http://www.naxja.org/forum/showthread.php?t=1050783

From trouble shooting the last 5 days.

The problem is I only have .28 V on the AC scale of a quality, high impedance multi meter showing up on these jeeps for the mounted, isolated CPS (some call it the CKP), CranK Position sensor. When connected to the harness I have a higher voltage AC / DC signal, due to a voltage from the ECU. Others here say the mounted, but electrically isolated CPS should be .5 to .8 volts. My 21 year old CPS was down to .18 Volts, AC when we decided it was the reason for a no start problem. But it failed to start after replacing the CPS. While troubleshooting further, during a fuel pressure test.....after other tests, it finally started, and has started a good 30 times in a row now, but I am concerned that I may need to force the CPS closer to the flexplate teeth to get a higher voltage, to make sure it will run and start reliably in the future.

So, for those of you with a running, or non running Renix would you please go gather some current test data for me, and for all of us historically to see what all our current CPS voltages are?

Test one is the disconnected CPS, AC scale on a high impedance meter, 0-1 volt scale while cranking:

Test 2, the AC and DC voltage on a 0-5 volt scale (or autoranging), of the CPS voltage while cranking (pull the primary HV spark plug wire from the distributor to keep it from starting), with the CPS connected to the wiring harness. You will need to back probe for this test through the weatherpack or wire insulation.

Test three would the engine running voltages AC & DC same as step 2, except with engine running.

Lastly repeat steps 2 & 3 at the ICM High Voltage module with the single yellow wire on the left connector to the ICM (Ignition Control Module), the 2 wire connector that has just one yellow wire.

Thanks!!!

My:
Test 1 data was .280 Volts AC
Test 2 data was 1.62-1.68 Volts AC
Test 3 data was 1.2 AC volts, and .8 DC volts

My experience from the early days at the dealership when these rigs were new is: 500MV AC at the CPS connector on cranking. 350MV or less can cause intermittent crank no start.

FWIW, there was a bulletin to bypass the CPS wiring away from the notorious POS, the C101 connector. Search "CPS bypass" or I can provide you the bulletin. I just do my own bypass with solder and shrink tube. I can describe it to you if you like.

cruiser54 said:

My experience from the early days at the dealership when these rigs were new is: 500MV AC at the CPS connector on cranking. 350MV or less can cause intermittent crank no start.

FWIW, there was a bulletin to bypass the CPS wiring away from the notorious POS, the C101 connector. Search "CPS bypass" or I can provide you the bulletin. I just do my own bypass with solder and shrink tube. I can describe it to you if you like.

Click to expand...

No thanks, not needed. If they run with .28 volts I don't have a C-101 problem on the 87, and the 89 does not have the C-101. Thanks. But, how did you get .5 volts AC and higher? I just installed a new one and I am only getting .28 Volts AC, and so far it is working? I did reuse the OEM grommet that was still over the hole! It worked that way for 120,000 miles and 21 years, so I did not see any reason to remove it, also it helps avoid dropping bolts in the bell housing :shiver:. Also the 6 year old CPS on my 87 is reading .28 volts AC, the same as the new one!!!!

cruiser54 said:

My experience from the early days at the dealership when these rigs were new is: 500MV AC at the CPS connector on cranking. 350MV or less can cause intermittent crank no start.

FWIW, there was a bulletin to bypass the CPS wiring away from the notorious POS, the C101 connector. Search "CPS bypass" or I can provide you the bulletin. I just do my own bypass with solder and shrink tube. I can describe it to you if you like.

Click to expand...

Did they ever test the live running voltage of the CPS, engine running?

IIRC, just cranking with the CPS unplugged. We drilled out one mounting hole of the CPS to move it closer to the flywheel/flexplate so it would generate a higher voltage signal. At .250, we had intermittent crank no starts, all the way up to .350.

Getting back on track, I still need mulitple reports from working Renix rigs, CPS voltage data please! Test data while cranking wires loose from the harness, and while running. Anyone have time to got test their working Renix CPS for me? To repeat:

I need a favor. I am trying to decide if I should use the "if it ain't broke don't fix it" theorem, or if both my Running Renix jeeps are likely to give me further CPS no start, died on the road trouble again any day now. I have a detailed thread with detailed CPS to ICM voltage test data on my 89 and 87 Renix Jeeps, here:

http://www.naxja.org/forum/showthread.php?t=1050783

From trouble shooting the last 5 days.

The problem is I only have .28 V on the AC scale of a quality, high impedance multi meter showing up on these jeeps for the mounted, isolated CPS (some call it the CKP), CranK Position sensor. When connected to the harness I have a higher voltage AC / DC signal, due to a voltage from the ECU. Others here say the mounted, but electrically isolated CPS should be .5 to .8 volts. My 21 year old CPS was down to .18 Volts, AC when we decided it was the reason for a no start problem. But it failed to start after replacing the CPS. While troubleshooting further, during a fuel pressure test.....after other tests, it finally started, and has started a good 30 times in a row now, but I am concerned that I may need to force the CPS closer to the flexplate teeth to get a higher voltage, to make sure it will run and start reliably in the future.

So, for those of you with a running, or non running Renix would you please go gather some current test data for me, and for all of us historically to see what all our current CPS voltages are?

Test one is the disconnected CPS, AC scale on a high impedance meter, 0-1 volt scale while cranking:

Test 2, the AC and DC voltage on a 0-5 volt scale (or autoranging), of the CPS voltage while cranking (pull the primary HV spark plug wire from the distributor to keep it from starting), with the CPS connected to the wiring harness. You will need to back probe for this test through the weatherpack or wire insulation.

Test three would the engine running voltages AC & DC same as step 2, except with engine running.

Lastly repeat steps 2 & 3 at the ICM High Voltage module with the single yellow wire on the left connector to the ICM (Ignition Control Module), the 2 wire connector that has just one yellow wire.

Thanks!!!

My:
Test 1 data was .280 Volts AC
Test 2 data was 1.62-1.68 Volts AC
Test 3 data was 1.2 AC volts, and .8 DC volts

To summarize again, what bothers me is that if I use the .8 volts DC my meter reads on the running rig, and subtract it from the 1.62 AC I got, I get .8 volts above the DC reading. I also get I presume is +/-1.62 volts AC that is twice what others have parrotted here as targets... So I am wondering if that (1.62-.8=.82) is the .8 volts people are parroting here as the proper voltage, or not, but no where does anyone say what the old .5 to .8 volt data was measured with, since the CPS does produce a true 60 cycle AC voltage.

So folks, I think it is time several of us took some readings, and built a data base of running data here today!!!! For future reference!!! Thanks!