1990 Renix FI - Random Engine Shut Down
 

I am not sure this belongs here in the "stock" section, but it really didn't seem to fit in the Modified either, as i was not finding much engine related stuff there..... If it needs to be moved, please let me know, I'll delete this thread and restart it in the Mod-Sec

Engine Back Ground:
I had a 90 XJ, 4.0 AW4, it spun a rod bearing... So i built a 4.7 stroker back in 2007/2008 utilizing JeepStroker.com, Pirate4x4, and a few other Strokercentric websites...
Stroker Build basics
.06 O'bore
.01 Decked head and Block
Crane Cams 753901 Cam Adv Duration = 260/272, Lift at Valve = .456/.484
Ford SVO 24lb/h injectors


Old Story, Jeep ran great for many years...

Newish Story, i couldnt run with guys in my club any longer on the old XJ, the HP44 & 9" couldnt handle the abuse i was dishing out them with the 37's and the chopped and extensively caged Unibody was failing in places i didn't want to fix again...


So i built a TJ based buggy using my Stroker, and a newly acquired AX-15D (euro diesel version with a 4.3 first gear), a 14b and D60 on 42's.....
I gutted the wiring harness, removed all the unnecessary stuff from the AW4, and any thing else not engine operation/calibration/diagnosis related.


This rig has been done and wheeling for 5 years now... I had chased many issues with Engine Tuning and Operation, but finally got it all sorted out about 3 years ago...

Now i have a new problem that I am at my wits & pocket books end with.....

The Storker on Renix runs smooth, efficient and like a champ.... Until it doesn't. And when i say "like it doesn't", I mean it shuts down mid operation like i shut the key off.
It doesn't matter if its at an idle, in warm up, at full op temp, mid throttle, or being whipped like a rented mule. It just shuts off.

I not have completely gone thru the wiring, from switch panel to connectors. However, i have verified REF voltage at all sensors, (4.93/4.85Vdc) and checked resistance & condition of grounds from Engine to Body, Engine to Bat, and Body to Bat.
Replaced the entire distributor, ignition mod, crank trigger, & MAP.
I have verified proper operation & specs of, Throttle Position Sensor, Idle Air Control (while checking these i c, Coolant Temp Sensor, & the Intake Air Temp Sensor....
I have verified proper Fuel Pressure, and Relief/Regulator operation.

I hadn't found cruiser54's "Book" until earlier this week. I have started on the list, going thru steps 1-5.... just to be sure....

@crusier54 holy bawls thats alot of info. Thanks for being a proponent of the Renix System, it has served me well, and i would rather like to keep it due to its simplicity and robustness.

for reference i added a pic of the Donor XJ, and the current TJuggy....
https://cimg5.ibsrv.net/gimg/www.che...f33ca6a585.jpg
https://cimg3.ibsrv.net/gimg/www.che...71f4da2b19.jpg

You're on the right track. Tips 1 through 5. also test your cPS.

CPS.... As in the Crank Position Sensor, or Cam Position Sensor?

Crank Position is brand new.

Crank Position Sensor. New doesn't mean it's good.

Renix has no Cam Position Sensor.

Here:


https://i1.wp.com/cruiser54.com/wp-c...size=300%2C169

https://i1.wp.com/cruiser54.com/wp-c...size=320%2C329

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 itself as shown in Figure 2 as Connector A, 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.

Another little tip to save tons of aggravation is to stick a bit of electrical tape to your 11mm socket and then shove the bolt in after it. This reduces the chances of dropping that special bolt into the bell housing. https://i1.wp.com/cruiser54.com/wp-c...size=300%2C224

I'll check the "CPS" Crank Trigger voltage after breakfast. The one I bought is a "Standard" brand, same that you would get from NAPA, or CarQuest. I've never had a problem with Standard, but I do agree with the fact that other cheap brands could be suspect. I've run into those things myself in the past

Crank Trigger / CPS / Engine Speed Sensor
.485 average on 3, 3 second crank trials.

Verified grounds to battery from:
CTS - 1.0
TPS - .8
IAT - .6
MAP - .6
O2 - .6
Knock Sen - .7
Synch Sig Gen - .5
Ign Pwr Mod - .6
D-Port - .7
DipStick Post to Bat - .5
Body to Cage in cockpit - .6
Body to Cage under hood - .7
ECU Connector D3 to sensor connectors = .6 to .7 @ IAC, TPS, MAP, & CTS
The #'s above have .1 ohm initial resistance from my fluke leads subtracted.

While checking ground resistance, i also disconnected and cleaned each connection, then rechecked to document any change in resistance. No connection had more than a .1 ohm delta between pre & post cleaning.

I also removed and cleaned all Relay connections, the ignition/starter relay was had some pretty loose connections, and the ground spade was pretty tarnished. I cleaned it, and will be starting and letting the rig run after i get home from a honey do trip with my wife....


I assume the low resistance i have in the sensor ground circuit is OK, if not, I will go and replace the ground connections in the harness. I did this when i built the harness 5 years ago, and they are still tight, soldered solid and were dry as a bone when i peeled the rubberized shrink tube back that i used when i built it.

https://cimg7.ibsrv.net/gimg/www.che...066aef9595.jpg
Those are nice results. How about the 4 relays in a row? Did you clean them and their receptacles? Take a gander underneath there with a mirror and see what you find.

I did. The bases are dirty, but not corroded on the under side. I had cleaned and coated them with battery terminal grease when i put the harness together.
I am in process of pulling the terminals from each base, verifying they are corrosion free.


All relay terminals were clean and corrosion free, now they are all scrubbed/polished/tightened if needed and reinstalled.
There was little to no tarnish, no "loose" relay connection terminals per say, i did however make sure all the contact tabs were touching the back side of crimp prior to relay install, just to be sure they all had a tight connection. I found no loose wire crimps, or any corrosion on the crimps. Did find one wire with cracked insulation, (F22-OR) from splice # F22-3 to the relay base. I repaired the bad insulation with RTV and shrink tubeafter confirming no broken wire strands. I think this cracked when i wrenched the relay pack up out of its mounted location.

Now i have a no start condition....

Move all the relays over one receptacle. The fuel pump relay could be bad.

Fuel Pump Relay is Good. Pulled, check via jumper to battery, FP runs and provides 39psi at fuel rail.


i should add, the FP circuit is not in the ECU controlled circuit. It is, and has been in a separate manually controlled circuit, and has been since this harness/system was in the old XJ 10+ years ago.


I have spark at cylinder 1.
I have FI pulse signal at cylinder 1.



Is it possible that the ECU forgot its parameters while the battery was disconnected? There is a very good chance that while i had the positive post disconnected, the + terminal made contact with a ground. IIRC correctly, grounding the + terminal will discharge the capacitors in the ECU, which under that condition will erase the ECU "memory"


Edit 12:36 - Moving on to Tip 13, Dist Indexing. Only to verify the distributor index/firing order is all in line... and not just far enough out to cause a difficult start situation.

Edit 1:05 - Dist Indx complete. Factory forked location had rotor centered on #1 terminal, Now advanced to Tail end of rotor aligned with terminal post 1.


After a 5, 5-8 second cranking sessions, it started. Runs a little rough, but it is smoothing out as it idles...



Now to see how long it idles, and if i can recreate the shut down issue.

Been idling for nearly an hour now. I have attempted to get it to stall/shut down by wiggling and down right pulling and shaking on the harness from out to each sensor/relay/harness junction.. it will not quit...


Even though is sounds a bit smoother and less "cammed" or choppy that it did before, it still has a slight stumble you can hear in the exhaust note....

Renix has no memory. I wonder why it's running rough. Fouled plug or two?

MAP sensor hose has good integrity? If not, rich running.

New plugs and wires.
pulled them after an hour of idling. They are med dark brown and dry. Not light clay brown colored as I'd like to see them, but not wet/fouled for certain.

MAP is new.
Vac hose and fittings are good.
No vacuum leaks that I could find with starting fluid. And no exhaust leaks....


I shut it down after an hour of idling in the driveway, it fired right back up. Let it sit and cool, fired right up when I pulled it inside.inside.

Maybe a bad HEGO.... I'll check that tomorrow....


Thanks for all the help thus far, it is very nice to have a knowledgeable person to work thru this with

HEGO could be rough idle.

Starting pretty good now though?

Seems to start quicker cold and warm. Not sure I can quantify the amount though.