Renix, pre-91 era XJ jeep tech differences

[cruiser54]

I know, was just joking. I was always afraid of Renix until I helped a friend bring back a 1990 that should have gone to the crusher. I'm more comfortable with them once the exploding coolant bottle is gone (HO cooling swap).

True stuff right there. LOL.

Ditch the plastic heater control valve also!!

 

[Miller88]

Heater control valve was thrown in the junk pile along with all of the factory vacuum lines. Only vacuum lines that are left are just the basics. No HCV, CAD ... airbox flipper.

New Cam chain, grounds, indexed TPS, opened up crank sensor, new vacuum lines and it runs real good.

 

[kastein]

In 1991 Chrysler kept most of the basic Renix fuel injection system, but used their own ECU computer and changed the engine head (it is called an HO meaning High Output). Other minor changes were made here and there.....

96 was a great year for the XJs. One of the best

96 is great except if you're in the rustbelt, then the fuel sender assembly is a real sticking point because they are unobtainium and only work with that one year.

Try this:

http://www.ebay.com/bhp/weather-pack-connector

I think that one, like most of the others was a GM weatherpack. I know the 87-90 connectors, most of them were. I looked at mine on the headlight harness recently and it was about 6 or more wires, flat connector, and IIRC it was also a weather pack.

They are dirt cheap, on ebay, from China and very high quality. I stocked up a huge hoard of them about 8 years ago when 5-90 gave me a clue to follow.

Unfortunately I don't think it is. I do wiring harness and electronic control module design at a small aerospace/automotive R&D firm and I've spent entire evenings looking through my Delphi weatherpack, metripack, apex, 56, 58, and basically every other connector series catalog I could get my hands on. No dice so far.

IIRC it is a 10 pin connector. A friend said it might be similar to one he's seen on some Jaguars and/or Rolls, but I've come up empty handed chasing down that info as well.

Correction on the meaning of HO:

HO myth buster


Renix in 90 made 182 HP. HO in 91 made 190 HP. That's 8 HP difference.

HO only made more HP than Renix at higher RPMs and not a bit more torque. HO had 58 mm throttle body versus a 52 mm throttle body on a Renix and also had a better design header. See where I'm going with this?

The whole 8HP was not mostly from the head, but from the bigger TB and better exhaust manifold.

Put a 60mm TB from www.strokedjeep.com on your present head, eliminate the "crush" in your headpipe with proper re-routing, and go for it.

HO stands for Highly Overrated.
__________________

Agreed, but I'm somewhat annoyed by a lot of the stuff on a RENIX now that I own one. The internally regulated alternator's a minor annoyance (I'm a picky EE, most people probably won't care), the throttle body design and intake hose annoy me, the TPS and CPS are FAR more susceptible to failure and water issues than I'm used to from owning a 91, a 96, and a 98, and the wiring harness is minimally waterproofed and not thought out very well. A lot of this can be chalked up to it being an 80s design - things have progressed significantly since then - but I never understood why a lot of RENIX owners say "it's always the CPS", replace TPSes every time they go mudding, and swear by cleaning connectors and packing them with dielectric grease. I've never had to do any of that on an HO. My 88 MJ sat for a couple years in my yard and I couldn't figure out why it was unable to start until I threw an oscilloscope on the CPS... sure enough it was dead. Worked fine when parked :dunno: then after that it would barely run right and would stall if you dropped the throttle, which turned out to be a completely dead TPS, which again worked fine when parked. I might be just a little bitter about that :confused1

 

[Green Mesa XJ]

Here is what the headlight harness connector looks like (headlight side).ill compare them to the eBay link when I get a chance. But yeah the plug is ten terminals, for sure the ones on eBay are used a few other places under the hood.

Sent from my iPhone using Tapatalk

 

[Ecomike]

Th largest flat GM weather pack, 1980's era I see available is 6 pin. If I ever need tangle with mine will just use a pair, a 6 and 4 pin one that I can buy. The 10 pin flat design was a mistake, too hard to pull apart with out damaging it..

The Renix CPS uses a so called permanent magnet that looses it field strength with age. Later years use a something else as I recall.

 

[kastein]

It's not the magnet that changed - the 91+ use that too. Basically the RENIX uses a coil of wire as a magnetic pickup while the HO uses a powered Hall effect sensor that just spits out a 0V-5V (or is it 7V? I can never remember what the sensor power rail the CPS runs on uses) square wave with the edges corresponding to the edges of the gaps in the flywheel or flexplate. It can signal effectively all the way down to zero RPM - you can stop the flywheel anywhere and it can tell you if it's over a gap or a solid spot without moving it. The RENIX setup with the coil means that due to how the laws of magnetism work, the faster the magnetic field through the coil changes (AKA the faster the flywheel is moving) the more voltage it outputs. So it'll output nothing if the engine is stopped, whether it's over a slot or a metal spot, and if your battery is weak it may not crank fast enough to get enough CPS signal voltage for the ECU to recognize the signal. That's why the capacitor trick sometimes works, and why the "push the CPS closer to the flywheel" trick works (reduce the airgap and you increase the peak field strength, which means the field changes more at a given cranking RPM and thus the voltage from the CPS peaks higher!), and also why RENIX jeeps sometimes take a couple cranks to start, while HO usually start the second they know where they are - which is probably going to be when they see the first slot in a group (there are 3 groups of 4 slots on an HO flywheel - each corresponds to one of the pairs of cylinders, since an I6 is basically two I3 engines back to back, you can tell which of the two is coming up to compression TDC and which is on exhaust TDC using the cam position sensor.)

The whole reason CPS sensors have a magnet in their tip is because of how magnetism works. You have to have a magnet somewhere to create a field, you can either glue a row of magnets to the flywheel edge so they trigger the sensor by changing the field strength as they go by, or cut slots in a regular old cast iron flywheel and put the magnet on the sensor tip, which also makes the field strength change as the slots go by since the air doesn't have the same magnetic permeability as the iron does. It's far cheaper, more durable, and more precise to machine the slots and put one magnet on the sensor, so basically every single automotive OEM in the world does it this way, it's just a matter of whether they use coil pickups or Hall sensors. Coil pickups are all 2 wire, some Hall pickups are 2 wire and some are 3 wire.

If anyone really wants to know more about this, I might throw together a thread about it. As I said I work as an electrical engineer at an automotive/aerospace firm, and my girlfriend is a failure analysis engineer at a major automotive Hall effect sensor manufacturer, so I've got a bit more info about how CPSes, cam sensors, ABS wheel speed sensors, fan clutch RPM sensors, etc work sitting around the house than most people do :spin1:

 

[Ecomike]

Yes, you should do a thread on this, thanks, great info!!!

 

[Ecomike]

So as the magnets loose their original strength, the Renix set up would see less voltage than the HO since the HOs (using hall effect sensors) do not depend so much on the magnets strength?

The HOs either work or do not, all the way down to zero rpm while the Renix needs a solid cranking RPM just to generate enough voltage for the ECM to see when it is new. Big difference between .5 volts for Renix and 5 volts for HO. I remember computer contacts having issues when they dropped to 5 volts in the late 70's early 80s. They had to switch to gold plated contacts.

0.5 volts must have been a real trick and issue for Renix wiring using AMC wiring LOL.

 

[kastein]

I don't know if the magnets lose strength. HO Hall sensors normally work fine till they start having the same thermal failure mode as RENIX ones, then die completely. I've honestly only killed one, and it got so hot (failed torque converter and transmission) that the plastic housing melted so I'm not at all surprised it died.

 

[Ecomike]

I don't know if the magnets lose strength. HO Hall sensors normally work fine till they start having the same thermal failure mode as RENIX ones, then die completely. I've honestly only killed one, and it got so hot (failed torque converter and transmission) that the plastic housing melted so I'm not at all surprised it died.

I am no expert on magnets either, but I read tons of info on the subject decades ago, forgot most of it since, I just recall reading something about how some magnets, maybe not all, do loose some strength over time, How much? I do not recall. I did dissect my first dead aftermarket Renix CPS and was shocked at the massive length of extremely fine wire in the coil, Was close to or thinner than human hair. Still have a photo of it saved here. The wire could easily be the point of failure, or the connection between that core coil wire and the external connector wires. Could also be the cause of new ones that are bad off the shelf.

 

[Devilfrog]

Gets one to thinking ...
Would it be at all possible to run a metered voltage (adding that third wire into the mix) to an HO CPS, and have it work with a Renix then? The Renix CPS uses a common connector (weatherpack) and has a third pinout going unused.

As for the early headlight harness ... Has anyone looked at Motorcraft (Ford) connector sources of the era? The distributors were a Motorcraft based design and given ABC's habit of grabbing whatever they could get their hands on ...
And regarding Renix TPS's they are simply a Th32 with a different wire arrangement ... The GM 2.8L V6 tps from 86-94 can be used with a simple wire placement change. And for the manual trans folks even cheaper than the auto TPS commonly used. I've been running one I pulled from a JY motor for the last year and a half.

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[old_man]

I am no expert on magnets either, but I read tons of info on the subject decades ago, forgot most of it since, I just recall reading something about how some magnets, maybe not all, do loose some strength over time, How much? I do not recall. I did dissect my first dead aftermarket Renix CPS and was shocked at the massive length of extremely fine wire in the coil, Was close to or thinner than human hair. Still have a photo of it saved here. The wire could easily be the point of failure, or the connection between that core coil wire and the external connector wires. Could also be the cause of new ones that are bad off the shelf.

The sensor you are looking at is a variable reluctance type. They send a small current through the coil which makes it an electromagnet. As you pass a ferrous object through the field, it will cause a change in the current for an instant that the computer can sense. Another variant uses a magnet and a field winding. As you pass a ferrous object near, it varies the field coupling and causes a voltage change.

 

[87manche]

The RENIX setup with the coil means that due to how the laws of magnetism work, the faster the magnetic field through the coil changes (AKA the faster the flywheel is moving) the more voltage it outputs.

this difference is why the motor needs to see 300 RPM while cranking to fire.

 

[kastein]

Gets one to thinking ...
Would it be at all possible to run a metered voltage (adding that third wire into the mix) to an HO CPS, and have it work with a Renix then? The Renix CPS uses a common connector (weatherpack) and has a third pinout going unused.

As for the early headlight harness ... Has anyone looked at Motorcraft (Ford) connector sources of the era? The distributors were a Motorcraft based design and given AMC's habit of grabbing whatever they could get their hands on ...
And regarding Renix TPS's they are simply a Th32 with a different wire arrangement ... The GM 2.8L V6 tps from 86-94 can be used with a simple wire placement change. And for the manual trans folks even cheaper than the auto TPS commonly used. I've been running one I pulled from a JY motor for the last year and a half.

Sent from my SGH-I337M using Tapatalk

Can't really do that. The HO CPS is DC in via 2 wires (power, ground) and then the output is a square wave on the third pin referenced to the ground pin. The RENIX CPS is an AC sorta sine wave setup and varies in both frequency and voltage. You might be able to rig it, but IIRC the RENIX setup and HO setup are ~90 degrees out of phase since the RENIX signal crosses zero at the centers of the slots while the HO signal has an edge at each end of each slot.

I'll have to take a look at the Motorcraft connector line, thanks for the tip.

 

[Ecomike]

The sensor you are looking at is a variable reluctance type. They send a small current through the coil which makes it an electromagnet. As you pass a ferrous object through the field, it will cause a change in the current for an instant that the computer can sense. Another variant uses a magnet and a field winding. As you pass a ferrous object near, it varies the field coupling and causes a voltage change.

The Renix one I opened up in the photo had a small magnet, and as most of us know is voltage change type you mentioned.

Thanks for the education on types and how they work!!!!

I have used (systems I designed and built) various proximity sensors for liquid tank level sensors through plastic tank walls, over the last 40 years but never got deep enough into exactly how they work. I still have a few gaps in the EE/physics field I want to fill someday in this lifetime.

 

[sjx40250]

Hi all. It has been a few years since I have paid attention to my XJ and been on this forum. I am also an avid C&V bicyclist and have had my head and heart in that vein.

To answer the OP, I have a 1990 XJ Laredo bought new in May of that year. It is the 4.0 with AW4, NP242 with towing package. Here is what I have done to it since and it is in not particular order as my memory isn't as good as it once was. The list covers changes from stock. If it is not mentioned, then it is still stock.

1. The fuel injectors started to leak. They were replaced with Bosch Greenies form Motor Sport 50 (is that the right name?).
2. Borla exhaust from header to tail pipe. Still going strong.
3. High flow cat.
4. KoolFlow water pump. Went through 3 before changing. This coincided with coring the radiator which was 30% blocked. That was many years ago and since the cooling problem disappeared with these two changes, it still has the closed system.
5. Head job due to failing valve seals. While I had the head off, I replaced the con-rod bearings, Broke the glaze on the cylinder walls and replaced the rings with cast iron ones.
6. Because of the new injectors and the header, it failed emissions test in Oregon,which got those Texas dyno's. I installed the adjustable MAP circuitry, and use Splitfire plugs. That was the only way to get it to pass. It still has this configuration.
7. Replaced the rear axle with one that had 10 inch drums and trac lock. Slightly more surface area.
8. The temperature sensor went bad or something between it and the bulb. It's function was replaced with a newer thermostat housing with the temp port and an aftermarket sensor used to control the fan. The fan now comes on anytime to cool even without the ignition turned on. I have not lost a battery as a result.
9. The track bar broke right above the pumpkin! Couldn't believe it! Replaced with an adjustable one from RE.
10. The TRE's got worn out so the linkage was replaced by Keven's stuff.
11. AC was simply upgraded with new ports with R134. It works but not great. I might explore upgrading the system.
12. Found a front sway bar in 19mm and swapped it in.
13. You are going to cringe but I added 2.375 inches to the front by buying 4" black pipe (abs or pcv?) with an end cap. The pipe is cut at the edge of the cap, giving 2" of lenght and double thickness. A hole is cut for the shock and installed between the donuts (have two) and the body. Works great and will not fail. The rear springs have helpers on them as part of addressing sag when towing.
14. Replaced failed horns with air horns
15. Replaced the horn button with the one that has cap screw heads around the circumference.
15. Privacy glass replaced the stock clear glass.
16. New speakers in the front doors.
17. Replaced the stock fog lights with Hella's

I am now seriously considering bringing this thing back to reliable working order. It is a project worth doing as I still love the way it drives (Koni shocks). I still get 21 on the highway and it doesn't use any oil with pressure around 25 running and more than required idle.

Project would include:
1. New rear springs. I have a pair of add a leafs but might just get all new springs. Going for 3.5 lift.
2. Do something with the rear end. I have a carrier for higher ratio gears. Currently at 2.54. I would like to add a locker. Dream would be a 44 or bigger axles.
3. Adjustable track arms to go with the lift.
4. New headlight wiring for more light
5. Ground fix? Don't know what that is.
6. Power Window fix. I have the write up in a 3 ring binder somewhere.
7. Upholstery. I have a tear on the drivers seat and everything look a bit dirty.
8. Replacement plastic parts in the cabin, specifically the cover holders and the parts covering the D pillars, if possible. Anyone know where to get a new bezel for the auto stick?
9. AC upgrade?
10. Replace the air horns.
11. May replace the shocks or figure out how to change the mounts to move them for the lift.
12. The remote key failed so I am thinking aftermarket
13. Rear speakers.
14. New head unit for sound.
16. New head lights.
17. Off road bumpers with external tire mount
18. Roof Rack.
19. Biggest tires that will fit in a 3.5 inch lift. May need to space the wheels out.
20. Repaint.

BTW. I had a leak for a couple of years that I could not find. It was the seam between the roof and the rear quarter panel under the chrome strip. This after a quart of sealant around the rear window and a new seal for the hatch. Found it by localizing water flow from a hose after stripping the interior storage to see where the water flowed from.

Well that's pretty much all that comes to mind.

Oh yeah, Good to see some long time user names in this thread. Respect to all of you.

 

[Ecomike]

Welcome back!!! Another Renix lives!!!!

 

[sjx40250]

Thanks! I have a 98 with an UpCountry package and towing that nearly identical but is a Classic trim. I really like that one too. It has its own issues related to AC and power locks, otherwise a great riding vehicle.

Since someone mentioned it. I too like the 80% torque off idle that the 90 has. The 98 is a bit different in the power band that is very subtle.

I had a 92 Limited that was very nice driver too. More miles and issues than either and I eventually sold it. In addition, I have owned a 97 ZJ with the 4.0 and currently have a 2000 WJ, which is good in its own market space, the last of the solid front axles that is not a wrangler.

Bottom line is that of all the jeeps the only other one I would consider is a 97 on up Wrangler series.

 

[Ecomike]

One thing I hate about the newer jeeps, non-XJs, (not sure about Wranglers, never drove one) is the massive rear view blind spots. The XJs, all of them have the best rear view, lack of blind spots of any vehicle I ever had. Has to do with the read side windows....

 

[mtbxj87]

I also had a water leak through the rubber well nuts that hold the factory rack tracks in place. Ultimately fixed it by taking those off and mounting my rack through the roof. 1"x .120" took the place of the tracks.