Renix CPS ? No spark

[Ecomike]

I cleaned up the (+) connections from the battery (+) to the starter relay (+) post, and all the in line fuse linked wire connections on the (+) post on the starter relay, and cleaned up the grounds at the oil dip stick.

I retested the ECU-CPS wiring and the two leads versus the battery negative post do read 5.6 Megohms, but read 9.6K ohms pin to pin in the harness. That is the norm it seems. So in a rush a few days ago, I got the 5.6 Meg Ohms thinking it was open (thinking I should be getting 9.6K ohms), when in fact I may have moved my meter ground to the battery due to back probing issues, not being able to get and keep good contact. So there may have been nothing wrong that day with the CPS harness connections for all I know.

I have just replaced all 5 under the hood relays, and cleaned the contacts. It never failed to start in all the tests today, even when I forgot to reconnect some vacuum lines after recalibrating the TPS (it ran up 2500 rpm) it still started. I ran a voltage drop test earlier today before cleaning the positive wire connections to the starter relay post, and I got a 10.6 V minimum there during cranking with the E-cooling fan on IIRC. I will retest the voltage drops again in a day or so. For now I need to take of other round to its. I have run repeated stall tests, and even lowered the idle to about 500 rpm in D or R, with AC and lights on, and it will not stall, even at 500 rpm.

I need to adjust the TB to correct uncle Bobs changes and do one last TPS calibration, and see where I am next. I also need to check the CTS and the O2 sensor to see if the O2 sensor is making me run too lean and messing with IAC control in the process.

 

[cruiser54]

Make sure the O2 sensor isn't lazy. That will cause a poor idle also, if it is lazy.

 

[Ecomike]

LOL, you make it sound like I should give it a kick in the ass if it has gotten lazy! haven't tried that one yet!!!!:roflmao:

Actually I have it idling smooth as glass now, almost like a new jeep.

Problem is I may not know for days or weeks if this "sudden death syndrome" and the sudden "I ain't gonna start no matter what you do to me syndrome" is truly fixed.

But I reset the idle stop and then the TPS and now the idle is a little too low, and I know it is not the IAC or TB or IAC sticking in the TB, which leaves a possible O2 sensor making me run too lean, which explains the high MPGs. But that is unrelated to the no start problem. It could have been related to the sudden death however.

 

[cruiser54]

Actually I think the O2 sensors fail in the rich mode. How long since you've put a new one on anyway? They're only good for about 80K IIRC.

 

[Ecomike]

Actually I think the O2 sensors fail in the rich mode. How long since you've put a new one on anyway? They're only good for about 80K IIRC.

I have no idea how old this one is, it came with the jeep. That is why I suspect it. Prior owner was getting 24 mpg highway. I got 20 mpg in city last tank before the no start, sudden death problem started. It passed smog tests here about 6 months ago.

 

[cruiser54]

Test it with the engine at operating temperature and see if it switches and how fast.

 

[Ecomike]

Test it with the engine at operating temperature and see if it switches and how fast.

O2 sensor is working fine. When you get a chance goggle "Ecomike O2 sensor" and read the old threads I put together here the last 4 years on O2 sensor testing. One thread I did is the "RenX Files", the other 2 were how to's on O2 sensor testing on jeeps.

This one is working flawlessly, used an a high impedance, FET, Analog meter.

One interesting twist I found is that my 89 ECU power feed to the O2 sensor built in heater is only 5 volts (same as the sensor feed from the ECU), and it works, only took about 20-25 seconds for the O2 sensor readings to kick into closed loop operation from a cold (40 F ) start up!

But my 87 Jeep has a 12-14 volt feed to the O2 sensors internal heater!

That was news to me, and may be every one else? There may be more going on there? It has implications on switching ECU's between 87 and 89!!!

 

[Ecomike]

89 jeep started and ran fine last 4-5 days. could not make it die or not start. This morning, 75 F, 95% humidity, my daughter trys to go to work, and no spark. I verified fuel OK, and no spark. Had no time to diagnose further. But did try unplug/replug CPS and TPS. I used a spark plug in line neon tester to verify no spark at the HV coil output post.

No doubt when I get home tonight to retest and debug, the nomad gremlins will be hiding again, and it will start.

I am convinced it is a marginal connection in a connector or an old semiconductor or circuit cold joint that is coming and going.

I am sure it is not the battery, not the grounds, not the TPS, not a dead CPS. It has started repeatedly with only .28 V AC signal while cranking, which is the same that I have for the 87 Jeep that has never failed to start in 4 years with the 4 year old CPS on it. I have wiggled the ECU connector and IIRC I had it off once and checked the contacts in it when I bought the jeep and they looked and acted new 2 years ago.

I am starting to think about swapping the ICM & coil from the 87 next. The 87 ICM and coil is only about 3 years old. The 89 ICM looks like the 89 OEM.

I hope it is still a no start tonight so I can trace the real problem finally.Hasta

 

[cruiser54]

Good luck. Might not be a bad idea to swap the ICM.

 

[Ecomike]

Last night was a repeat. Got home cranked up the 89 still no start. Back probed the CPS connector to read AC volts, cranked it and it started. I guess the CPS connectors are just anal, needed a little back probing to wake them up?:laugh3:

But this has happened twice, may 3 or 4 times now, so makes me wonder if the meter connection is doing something? Reminds me of thread from 2 years ago about how adding a capacitor across the CPS wires, parallel (IIRC) to the CPS helped boost the AC peak to peak signal of a weak signal.

I also noticed that the new CPS has an aluminum foil cover, EMF shield, around the two wires inside the outer insulation cover, but the Jeep harness side does not!

Now the water pump is showing signs of age (loose). I traced a noise down that has gotten worse during testing, was weak, come and went, not steady squeck-squeal, seems there is about 1/16"--1/8" from to rear play in water pump, and I can wiggle it side to side a little now.

 

[Ecomike]

Started right up this evening, no problem. Found a decent price on water pump at the AZone, new $34. Going to do hoses and serp belt while I am in there.

 

[Ecomike]

The 625 cranking amp, Valucraft battery, 2.5 years old, that has sat unused a few times this year for 1-2 weeks (parked) at a time showed its weak side tonight at around 40 F. It acts discharged after 60 seconds of cranking ( 5 times at about 12 seconds each), and acts charged after just 5-10 minutes of charging at only 6 amps!!!

I guess the gremlins lost their bearings again while I replaced the water pump, and moved on to the battery finally. This is turning into one of those never ending stories. :soapbox:

It would not start tonight after I replaced the water pump. So I hooked up the DVM to the CPS and it started. That is 4 out of 4 times it started right after hooking up the DVM!!!

I am replacing the battery and grabbing some .1 and .01 micro farad capacitors early tomorrow to try the capacitor fix trick on the CPS, if the battery does not solve it by itself!

 

[Ecomike]

New battery and it worked like a champ for 3 days. Started this morning, then refused to start tonight (no spark). My daughter was 45 miles across town at work, with another no start, ARGHHHH!

I drove over there, slapped a .045 uF capacitor across the CPS connections (in parallel) and it started on the first try.

Details on the capacitor trick are here:

http://www.naxja.org/forum/showthread.php?t=1051325&highlight=ecomike

This is getting very aggravating. I need a gremlin exterminating service, NOW!

So far, every time I had this intermittent, persistent no spark / no start problem, the DVM back probing or capacitor trick across the CPS (parallel) has gotten an immediate start / spark!

Tonight was warm, 100% humidity, rain! Most problem starts were cold weather, or rain.

 

[87manche]

I forget all the details in this thread, have you replaced the conectors? or just hardware it into the harness. SInce it happens when it's moist out I would really suspect something in the harness.

 

[Ecomike]

Everything runs and works once started.
New (in last 2 weeks):
CPS (old one was 89 OEM Renix, and only had .17 V cranking V AC on a High Imp. DMM)
Cap (brass, not Al)
Rotor
Plugs (AC Single tip platinum, same as have used for 6 years in my 87 Renix)
New HV Plug wires
New Heavy duty battery, 90 min reserve, AZ gold top

14.7 V at idle, 14.1 V at idle with all the E loads on Max (AC-Max, E-Rad fan, head lights on high beam, WS wipers...and so on)

All grounds and battery cables, cleaned, reworked, tested, less .1 Ohms battery neg post to any body - engine or sensor ground point or wire now

All relays under the hood brand new

Female sockets for relays all cleaned All connectors at the the starter relay near the battery cleaned.

Extra battery ground 4 Ga from Bat to frame near radiator, 4 ga from Head to rear firewall, 4 gauge from dip stick engine ground to battery, all sensors like TPS have extra 14 ga grounds run directly to battery.

CPS connector at harness was a brand new weather pack 2 weeks ago, been soldered for a week now (bypassed the weather packs).

Checked and cleaned and tightened fuse box fuse connections as needed.

Wiggled ECU connector. I think I pulled it and serviced the connector 2 years ago when I first bought it.

No Vacuum leaks.

IAC is only 3-4 months old. Less 5000 miles on it.

CTS. MAT, MAP, and O2 sensor tested live, all working with in factory specs.

CPS cranking voltage on AC setting on two meters is .28 V, same as my 87 jeep, which has always started, still has a C-101, and a weatherpack connectors on the CPS. The 87 CPS is an AZone sourced also, 4 years old, and the 87 started 2 days ago with a barely cranking nearly dead battery!!!

ICM is the old one, but has yet to test as the source of the no spark problem!

Replacing the CPS helped. Replacing the battery helped. Idle is smoother (Cap and rotor were on last legs).

When nothing else worked (after the new CPS was installed), no spark, no firing signal to ICM from the ECU, back probing the CPS connectors or adding a capacitor in parallel to the CPS has 100% of the time resulted in a start in 1-4 seconds of first crank!

It has worked for 1-2, 2-3 days at a time, then suddenly decided to act like stubborn POS!

At this point this jeep has turned into a regular 2-3 day extortion racket!

 

[kastein]

It's telling you that RENIX sucks and you should do a 91-95 swap

kidding, I'm betting on corroded wires or worn insulation deep in the harness somewhere.

 

[87manche]

Replacing the battery helped

this is rather telling to me that it's a ground/electrical issue. You've made sure the CPS harness is secured away from the downpipe?

Have you pulled the harness apart under the coolant turtle? You'll find all sorts of lovely mess there, mine had DUCT TAPED not crimped connections inside the factory outer wrap. Lots of ECU/injector power stuff runs through that bit of the harness.

 

[kastein]

They are actually crimped under the duct tape, it is just not easy to see under a thick layer of adhesive gunk.

For some reason AMC and Chrysler thought that crimping a brass ferrule over the wire and then folding duct tape over it was a good way to do a splice. Found that disaster inside the harness on a friend's RENIX MJ (originally a 2.5, hack-converted to a 4.0 by the previous previous owner) and thought it was some backyard mechanic job till I found the same thing inside the harness on my bone stock '98 XJ.

 

[Ecomike]

It's telling you that RENIX sucks and you should do a 91-95 swap

kidding, I'm betting on corroded wires or worn insulation deep in the harness somewhere.

The harness on this puppy looks brand new, like the day it came out of the factory, not at all like my messy 85 and 87.


Quote:
Originally Posted by Ecomike
Replacing the battery helped

this is rather telling to me that it's a ground/electrical issue. You've made sure the CPS harness is secured away from the downpipe?

Yes, the CPS wiring is secure.

The battery sulphated the plates setting up as a back up DD for 1-2 weeks between re-starts the last 6 months, and was a 2 year old barely adequit sized AZone Value craft cheap battery, bottom end battery. Not the Mama!

It started fine the last 3 restarts last night and so far today it started with out the Capacitor. I am planning to swap the ICM and Ign coil with my 87 next, as it is only 2-3 years old, the 89 looks like the 89 OEM. It has only failed to start once in the last 4 days since I installed the new battery.

 

[joe_peters]

I would like to recommend a Catholic Priest to perform an Exorcism.