AeroNautical Posted November 6, 2013 Share Posted November 6, 2013 I'm pretty sure I have it figured out, I need a new CPS and an O2 sensor, but before I sink $70 more into my 4.0 renix, I need to make sure. It takes several revolutions when engaging the starter, hot or cold, before it actually starts the engine, and on rare occasions it starts immediately. I figure it's the CPS, I doubt it's ever been replaced, but I have cleaned it very recently. When I do get the engine started, it smells like it runs very rich. No burning oil smell, TPS is adjusted perfectly, idles somewhat smoothly ( I think the CPS has something to do with that, also), and gas mileage isn't diminished as far as I can tell. O2 sensor going bad? Link to comment Share on other sites More sharing options...
cruiser54 Posted November 6, 2013 Share Posted November 6, 2013 Crank time is normal. If in doubt, check the CPS output. Renix CPS Testing and Adjusting Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark. Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad. The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark. Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected. You should get a reading of .5 AC volts. If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer. Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off. A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts. Revised 01-26-2013 Rich running is not caused by CPS. Most likely suspects are MAP, CTS, IAT. Guess what they have in common? Cruiser’s Renix Sensor Ground Test This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate. Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too. You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well. Revised 06/12/2012 Cruiser’s Renix Sensor Ground Test This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate. Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too. You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well. Revised 06/12/2012 Link to comment Share on other sites More sharing options...
AeroNautical Posted November 7, 2013 Author Share Posted November 7, 2013 So there's no chance the CPS and O2 sensors have gone bad? Sometimes when trying to run the engine the starter will turn for a good 5 seconds before it actually starts. I've done most everything on that list, but the few things I haven't done yet seem to be the problems I've been having as of late. Guess I should just take a day or two and do everything. Link to comment Share on other sites More sharing options...
Comanchepur Posted November 7, 2013 Share Posted November 7, 2013 :wall: Check the ignition position and all spark plug wires and check from battery to motor the positive wire and places to go it is sulfated the amps are no good have this problem. Another thing to check is the positive starter wire if do not have a good contact create situations too. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 7, 2013 Share Posted November 7, 2013 So there's no chance the CPS and O2 sensors have gone bad? Sometimes when trying to run the engine the starter will turn for a good 5 seconds before it actually starts. I've done most everything on that list, but the few things I haven't done yet seem to be the problems I've been having as of late. Guess I should just take a day or two and do everything. May be normal as far as the CPS. I'm advocating that you test it to either put it IN or OUT as far as an issue. Long crank times on a Renix Jeep are normal. What's "almost everything"? O2 sensor will not give you extended crank times. Could it be bad? Yes. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 7, 2013 Author Share Posted November 7, 2013 So there's no chance the CPS and O2 sensors have gone bad? Sometimes when trying to run the engine the starter will turn for a good 5 seconds before it actually starts. I've done most everything on that list, but the few things I haven't done yet seem to be the problems I've been having as of late. Guess I should just take a day or two and do everything. May be normal as far as the CPS. I'm advocating that you test it to either put it IN or OUT as far as an issue. Long crank times on a Renix Jeep are normal. What's "almost everything"? O2 sensor will not give you extended crank times. Could it be bad? Yes. I meant the o2 to fix the engine running rich, I wasn't sure if that would affect it or not. Almost everything as in I've done ground refreshing, connector cleaning, tps adjustment, but have never run new grounds like you mention above. I'll get on that and report back. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 7, 2013 Share Posted November 7, 2013 Do the sensor ground test along with the extra grounds. If you have never replaced the 02 sensor, they're supposed to be replaced about every 70,000 miles anyway. Link to comment Share on other sites More sharing options...
Knucklehead97 Posted November 7, 2013 Share Posted November 7, 2013 My truck was running rich and the o2 sensor failed the tests (very easy test to do) so I changed it and it no longer runs rich, or backfires, and I get around 20 mpg. I would change it Link to comment Share on other sites More sharing options...
cruiser54 Posted November 7, 2013 Share Posted November 7, 2013 My truck was running rich and the o2 sensor failed the tests (very easy test to do) so I changed it and it no longer runs rich, or backfires, and I get around 20 mpg. I would change it Good idea. Usual symptoms are a hunting idle also. But, with their limited lifespan probably a good idea to change it as you did. Need to look and see that the wiring harness isn't pulled out of it or the wires melted on the exhaust manifold. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 7, 2013 Author Share Posted November 7, 2013 I just did the Renix Sensor Ground upgrade, but had a question. When I splice the 2 sets of 3 brown and white wires, what do I do with the 2 single wires that remain? I read it a few times to make sure they weren't supposed to be spliced with the other wires, but even the picture points to no. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 7, 2013 Share Posted November 7, 2013 I just did the Renix Sensor Ground upgrade, but had a question. When I splice the 2 sets of 3 brown and white wires, what do I do with the 2 single wires that remain? I read it a few times to make sure they weren't supposed to be spliced with the other wires, but even the picture points to no. Where did those single wires go before? Link to comment Share on other sites More sharing options...
AeroNautical Posted November 8, 2013 Author Share Posted November 8, 2013 I just did the Renix Sensor Ground upgrade, but had a question. When I splice the 2 sets of 3 brown and white wires, what do I do with the 2 single wires that remain? I read it a few times to make sure they weren't supposed to be spliced with the other wires, but even the picture points to no. Where did those single wires go before? According to the write up they go to the C101 connector. But it has no mention of the 2 single wires after you cut the factory splice and solder the 2 sets of 3 wires together. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 8, 2013 Share Posted November 8, 2013 Unfortunarely, the number of sensor ground wires seems to have changed throughout the years. Check them with an ohmmeter to ground and see what readings you get. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 8, 2013 Author Share Posted November 8, 2013 Gotcha, thanks for the help cruiser, you fixed so many of my problems with those renix tips, hopefully this will continue that trend. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 8, 2013 Share Posted November 8, 2013 Gotcha, thanks for the help cruiser, you fixed so many of my problems with those renix tips, hopefully this will continue that trend. I didn't fix 'em. You did!!! Link to comment Share on other sites More sharing options...
AeroNautical Posted November 8, 2013 Author Share Posted November 8, 2013 Alright, I soldered the two remaining wires to the assembly, I figure a ground is a ground, right? Turns out, it was a good idea, she runs so smooth now, starts up within a second or 2, etc. Still smells rich, but I've got an O2 on the way to hopefully fix that. I have a question about your CPS upgrade, though. I attempted it with my old CPS, but the bar would not move. I don't want to break the damn thing, but am I supposed to go full force when banging at it? Link to comment Share on other sites More sharing options...
cruiser54 Posted November 8, 2013 Share Posted November 8, 2013 Alright, I soldered the two remaining wires to the assembly, I figure a ground is a ground, right? Turns out, it was a good idea, she runs so smooth now, starts up within a second or 2, etc. Still smells rich, but I've got an O2 on the way to hopefully fix that. I have a question about your CPS upgrade, though. I attempted it with my old CPS, but the bar would not move. I don't want to break the damn thing, but am I supposed to go full force when banging at it? Good news!! Are you wanting to advance the timing a bit, or just increase the CPS output voltage? 2 different tings. Sometimes the plastic on an old CPS will crumble away when attempting to slide it on the bar. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 9, 2013 Author Share Posted November 9, 2013 Would advancing the timing make enough of a difference to bother? I guess a better question is, what would it help? I was going to drill the larger holes to increase the output when the new one arrived. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 9, 2013 Share Posted November 9, 2013 It makes a little difference. All you need to do is drill the upper hole anyway to increase the voltage. You read this? Post 7? http://www.cherokeetech.com/VBull/showthread.php?3070-Cruiser-s-Mostly-Renix-Tips&p=103796#post103796 Link to comment Share on other sites More sharing options...
AeroNautical Posted November 12, 2013 Author Share Posted November 12, 2013 The new O2 and CPS sensors came in today. Installed them, and it starts right up, but holy hell is it idling rough. Does it take awhile for the computer to realize the O2 is new? The exhaust has high and low points, almost as if it's skipping. When I rev it to about 3000 and let it go it almost quits the engine, too. I really hope this will clear up in a few miles of driving... Link to comment Share on other sites More sharing options...
cruiser54 Posted November 12, 2013 Share Posted November 12, 2013 Renix ECM needs no training. Something else is wrong. CPS wiring on the exhaust manifold? Link to comment Share on other sites More sharing options...
AeroNautical Posted November 12, 2013 Author Share Posted November 12, 2013 No, made sure it had a good amount of clearance. Did a little more testing and it struggles to find it's idle. It goes down to about 300 and revs back up to 8 or 900, then back down again, over and over very quickly. When I give it power while driving, I can feel it pulsating a bit too, like I have normal torque, then lose it, then get it back. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 12, 2013 Author Share Posted November 12, 2013 Could it be a faulty O2 sensor? I got it from rock auto, same plug and threading as the old one, but the tip did look a bit different. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 13, 2013 Author Share Posted November 13, 2013 Well, I swapped in my old sensors and the problem persisted. I frantically look around the engine bay for something that may have knocked lose, turns out in my attempt to plug in the CPS, the brittle vacuum line to my MAP sensor broke without me knowing. A quick replacement and it runs strong, starts strong and doesn't run rich. An annoyingly successful days work.. Thanks again for the help Link to comment Share on other sites More sharing options...
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