More Renix No-Start (1990)

Before you say CPS: I HAVE SPARK!!!!

So I was going out to a client site down in socal after just driving down from WA in my 1990 XJ, parked last night over at my parents, this morning I saunter out, throw my tools in the car and start heading to work. Anyways, the vehicle started (but was running somewhat rough). I drive down the driveway and around the block to the main street... kapow vehicle dies and won't come back. Luckily it didn't happen on the drive down, or the drive back up.

Anyways, so far I've put a sensor on each of the plug wires, and it's showing I'm getting spark, regular and constant. I'm thinking this might be fuel related (going from non-ethanol PNW gas, to crap cali gas).

I'm not frustrated yet, but I certainly am annoyed.

I'm swapping the fuel filter right now, while I'm under there I'm going to check voltages and operation of fuel pump. I did check for presence of fuel in the rail, it doesn't seem to be getting the normal high-pressure spurt, which makes me think either fuel pump or regulator. (possibly ballast resistor)

I rented a fuel pressure gauge from vatozone, however it seems to be broken, measures zero pressure, and pumps gas everywhere. Oddly, it seems they had the presence of mind to epoxy the fittings onto the FP gauge so I can't simply remove the leaky part.

Anyways, I would appreciate any informed opinions about this, and yes, the CPS was the first thing I checked, so please for the love of God and all that is holy DONT SAY CPS.

Well you are on the right track. Maybe.

Is the spark HOT, BLUE, and SNAPPY? Quality of spark means a lot. You could always test the (BLANK).

The (BLANK) is the ONLY sensor that will kill an XJ. So, if the QUALITY of the spark is good, then move on from the (BLANK).

Definitely get a fuel pressure gauge on there--pressure AND delivery volume are both important.

Post up what you find.

Harbor Freight 92699, $19.99.

Joe,

Thanks for the post. Yea, CPS, CPS harness, and CPS everything are always my first go-tos on any renix XJ that's acting up or not running properly. However, in general, if you have regular spark, it's never the CPS. The problem with the CPS is that it's usually the source of the trouble, as a consequence it's nearly impossible to track down any of the other things that can create chaos and keep the XJ from starting because no one has documented it. It's kinda like high school algebra class where X was somehow always equal to 5. In this case, X is not the answer.

Anyways:

Ok, so new wrinkle... it starts! HORAY!!!!!

But only if I give it gas WTF?!

So that leads me to think... throttle solenoid? I'm sure EcoMike has already gone to bed, I'm positive he knows the answer.

I'm going to go dig in my parts bucket and see if I have a spare solenoid.

BulletMaker said:

Joe,

Thanks for the post. Yea, CPS, CPS harness, and CPS everything are always my first go-tos on any renix XJ that's acting up or not running properly. However, in general, if you have regular spark, it's never the CPS. The problem with the CPS is that it's usually the source of the trouble, as a consequence it's nearly impossible to track down any of the other things that can create chaos and keep the XJ from starting because no one has documented it. It's kinda like high school algebra class where X was somehow always equal to 5. In this case, X is not the answer.

Anyways:

Ok, so new wrinkle... it starts! HORAY!!!!!

But only if I give it gas WTF?!

So that leads me to think... throttle solenoid? I'm sure EcoMike has already gone to bed, I'm positive he knows the answer.

I'm going to go dig in my parts bucket and see if I have a spare solenoid.

Click to expand...

IAC could be stuck.

Have you bypassed the fuel pump ballast resistor on the driver's side fenderwell?

The Renix fuel pump gets its power in some freakish ways.

KOEO--fuel pump is energized for 2-3 seconds, and then power is cut by the CPU/PCM. KOECranking power to the fuel pump comes from the starter relay/PDC, bypassing the ballast resistor. KOER from idle to just short of WOT power is through the ballast resistor. WOT and power is from the o2 heater relay.

I think the IAC is the thing to check, ballast resistor tested OK. I replaced the fuel filter and while I was at it I energized the fuel pump by applying 12V to the connector and it dutifully pumped gas from the tank into my little gas can.

I also found this article when searching for "renix stuck IAC":

http://www.xjtalk.com/showthread.php?t=10844

Seems like a reasonable thing to do. I know I have a can of MEK or TCE around here that will remove all that garbage.

Ok, so I didn't go all the way (mostly because it got really late).

But I did pull the IAC, I cleaned the heck out of it with TCE and it looks almost new now. Then I got into the IAC barrel and cleaned that out the best I could with my pistol cleaning kit, and then sprayed in a bunch of rem-oil to loosen up the parts.

It's not perfect (idle is still lower than I would like) however the jeep is back up and in running condition. I'm going to pull off the throttle body this weekend and give it a good scrubbing and see if I can de-funk it.

Thanks for the help Joe.

The IAC being gummed up may be some of it or maybe even be all of it, but better than half the time when I start having IAC issues something is wrong with the charging system. Either the battery is getting weak or the alternator is putting out low voltage.

I'd also ohm out my TPS ground, the vast majority of my idle issues have been TPS or TPS ground issues.

Sometimes you have a few things a little out of whack and they add up.

Do you have oil in the airbox, it may be time to clean out the small plastic tube going into the top of your valve cover. If it plugs up, the motor tends to suck a lot of gunk through the intake (and IAC).

As a side note, I parked my Renix, hasn't been run in six months. Put in a fresh battery, checked the air box for vermin nests, removed the bird nest on top of my distributor, purged the fuel lines by jumping the orange wire with the black strip (fuel pump) on my starter relay to the main power lug for a minute. She fired right up and idled like a metronome.:yelclap:

It's probably worth mentioning that it's been acting funny (low on power) since the no-start. One thing I did while I was chasing gremlins was pressure wash the passenger side of the engine. I'm going to refresh the grounds, and clean all the terminal lugs tonight. I'm thinking some of this may be due to some recent work I did on the rear axle (replaced rear shoes, and I think they may be dragging intermittently) or possibly an issue with wheel bearings.

I had to drive it a fair amount last week, and it drove (it actually didn't die at all after cleaning out the IAC), where as previously it would get pissy if I started it, and then immediately went to drive it.

For good measure I also just put fresh plugs in it, so I'm leaning towards it being an issue somewhere else in the drivetrain.

It's also possible I'm just being overly critical, and that I'm anticipating problems that arn't actually there.

Here's the sensor ground test. Be sure to refresh all your grounds first.

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

Another good thing to do:

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals making sure they haven’t retracted into the plastic holder, and then plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one. Also be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.
ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then plug them back in. I do this on every Renix Jeep I purchase or work on for someone else.
Revised 07/23/2012

I pulled the idle air sensor, cleaned with chemtool, I also opened up the throttle body and went to town on it with chemtool and a rag.

Checked continuity (resistance) between negative battery terminal and engine components, it was <50ohm, but I pulled the grounding cable/terminal and cleaned that (on the engine behind the oil dipstick)

I then pulled the positive lug off the main bus where the vehicle power is supplied and cleaned all those off.

Fired right up, going to go for a test drive Wish me luck!

Have you ever read this, and seen what all grounds at the dipstick tube stud?

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 03-04-2013

Cruiser,

I think I've read it about half a dozen times

One of the first things I do to any renix XJ when I start working on it is get to chunks of 4ga, one goes to the engine, the other goes to the body. I replace the crap lead terminals with shiny new marine terminals, coat everything in dielectric grease, and then run a new 4ga down to the starter, 10ga to the power distribution point, and then refresh the alternator supply.

I think I'm going on 4 years with this jeep, and this is the first real "beyond normal maintenance" I've had to perform unexpectedly.

Also, it looks like my RMS is about to give up the ghost.

It's worth noting on the high speed drag race home power was back up and running. There was a bit of a hiccup at idle (waiting for a red light), the engine suddenly stuttered, and then got fluttery for about 10 seconds, and then got back to normal.

I'm starting to get some of my confidence back, which is good, seeing as how I'm going to do a straight 1300 mi trip next week (back up to WA) which I usually do in one shot, usually taking about 24 hrs.

Maybe later today I'll get in and start refreshing every connector I can pull apart, I think the heep is just mad at me for driving it into ca, feeding it ethanol blended fuel, and expecting it to put up with desert temperatures.