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No start RENIX, injectors not firing.

WrenchMonkey

WrenchMonkey

NAXJA Member #771
NAXJA Member
Location
East of Cincinnati
89 XJ, 210k, 10k on a new crate engine, with all new sensors for good measure.

It'll crank all day long, never fire, never smell gas.

It did this ten days ago, leaving work. Came back in the morning and it fired right up. Did it again last weekend. Poked around under the hood, pulled a sparkplug (dry) and it fired right up. This time it's done it for 24hrs+. All three times, it was after sitting 10+ hours. Never done it warm.

Fuel pressure seems good, gives a good healthy squirt outta the test port.

Hooked oreilly's test node to it, no flashes. Hooked the same one to my '00 "pretty jeep" and it did flash, so I think the node is good.

Old Man's FAQ says the only thing that'll kill the injectors is the computer. Others tell me a bad CPS might do that. I thought the CPS would only kill your spark, I dunno.

I don't have a good way to check for spark, no second set of hands to crank while I watch.


So? The computer? Stupid question, it's like below the glovebox, right?

Guy's parting a 90 on craigslist, over on the other side of town. What's a reasonable offer, y'think?

Thanks guys!

Robert
 
Found the computer, unplugged it, plugged it back in, just like Old Man said in the FAQ.

Fired right up.

Sorry for the premature capitulation!

Robert
 
I'd really suspect CPS failure as well.

ECU won't do jack without a CPS signal greater than 300 RPM.
 
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, 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 07-30-2012
 
Cruiser’s Renix ECU Connector Refreshing
Many times when other fixes have failed, it becomes necessary to eliminate the ECU to harness connections as a cause. This requires removing the ECU.
Up under the dash, to the right of the steering column is the ECU. It is held in by three 10mm headed bolts to a bracket. It’s most easily removed using a ratcheting wrench but a socket will work.
Once you get the ECU down, unplug the two harness connectors from it. Visually inspect the connectors and pins.
Using a good quality electronics cleaner, liberally spray both of the harness ends and the ECU pin area.
Now, take a small pick or a dental tool and go to the harness connectors. Using the tool, tweak each female receptacle in the harness plugs so they will grasp the ECU pins more tightly.
Plug the harnesses back on to the ECU and reinstall it. I usually only use two of the bolts because the third is a bear.
Revised 07/11/12
 
87manche said:
I'd really suspect CPS failure as well.

ECU won't do jack without a CPS signal greater than 300 RPM.
Click to expand...

Maybe. It's only 2yrs old, barely 10k miles, but it could be bad already...

But it fired IMMEDIATELY after I replugged the ECU. Don't see how that would "reset" the CPS...

cruiser54 said:
Up under the dash, to the right of the steering column is the ECU.
Click to expand...

Really? All years? 'Cause what I found and fiddled with was behind the dash panel, below the glove box and shelf, above the blower box. I'll get a pic when I get home...

Thanks again!
Robert
 
WrenchMonkey said:
Maybe. It's only 2yrs old, barely 10k miles, but it could be bad already...

But it fired IMMEDIATELY after I replugged the ECU. Don't see how that would "reset" the CPS...



Really? All years? 'Cause what I found and fiddled with was behind the dash panel, below the glove box and shelf, above the blower box. I'll get a pic when I get home...

Thanks again!
Robert
Click to expand...
was it yellow?

that's TCU location.
the renix box is above your right knee, big silver aluminum thing that looks like it would withstand an EMP.

edit:
and yes, sometimes unpluging and replugging a CPS will make it work a while longer.
 
WrenchMonkey said:
Maybe. It's only 2yrs old, barely 10k miles, but it could be bad already...

But it fired IMMEDIATELY after I replugged the ECU. Don't see how that would "reset" the CPS...



Really? All years? 'Cause what I found and fiddled with was behind the dash panel, below the glove box and shelf, above the blower box. I'll get a pic when I get home...

Thanks again!
Robert
Click to expand...

That was the TCU (transmission control unit) you fiddled with.

CPSs can be intermittent. CHECK the one you have using the instructions.
 
Go through and check the fuel injector ground in that subharness as well - it's common to all six.

I had a "floating ground" in my 87 a few years back that took me a while to find - the OEM connections are simple bare "strap crimps" covered with something resembling duct tape. I broke them out and re-did them with better connectors and sealed them with proper heat-shrink, and the problem went away.

If you're only losing the F/I pulses, that's where I'd go first (if the CKP fails, you'll lose both F/I and ignition timing. Every time.)
 
Plugged the CKP back in, wiggled the large firewall connector (C101?) and it fired right up.

I hate that it's something different each time, but maybe that is the tempermental nature of a CKP failure? Would it check good sometimes?

I dunno...

Robert
 
WrenchMonkey said:
Plugged the CKP back in, wiggled the large firewall connector (C101?) and it fired right up.

I hate that it's something different each time, but maybe that is the tempermental nature of a CKP failure? Would it check good sometimes?

I dunno...

Robert
Click to expand...

YES!!!! I had a brand new CKP (CPS) about 6-12 months ago, that acted good every time I checked it with a meter after a no start, it was OK, and then started after the meter test. Then one day, finally, I checked after a no start and it was open circuit, infinite resistance. Turned out to be a loose wiring connection inside the sealed sensor casing.


The ohms test is what it finally failed, not the .5V AC test!!!! On the ohms test it should be between 225 and 275 ohms IIRC.

Many people say the aftermarket ones are junk, and say to get OEM. I got my last good ones from Rock Auto, Standard brand, they were stamped made in Italy, last year.
 
Crap. I just bought the BWD from O'Reilly. $35 vs $21 for RA's Standard.

Oh well, I'd like to get this resolved this weekend, and if it doesn't go too badly (yeah right) maybe I'll swap it again for the Standard later.

Thanks guys...

Robert
 
Renix Jeep C101 Connector Refreshing
　
The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

Almost every critical signal between the engine sensors, injectors, ECU, and some to the TCU, travel this path through the C101 connector.
The C101 connector is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.
Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.
If you have a small pick or dental tool, tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter before bolting both halves back together.
　
Revised 07-17-2012
 
I just walked out the door an hour ago, the '90 won't start. It did the same three weeks ago, towed it home, sloshed gas in it, fired up. Won't this time.

http://autorepair.about.com/library/a/1i/bl637i.htm

Ran across this. I replaced the CPS a few years back and did the slot mod on one side, but this makes more sense. Out in the rain from Isaac to try it, and will report. I've also experienced the won't start from an old slow cranking starter - which tested good on the bench, but after 120K, I didn't trust it. The new one cranked right up.

Yes, it does take 300 rpm to count, and a good CPS mounted almost in touching distance to read.
 
It's bloody contagious!!!!! Lost my allspark last night!!!
 
I've been starting mine up (without issue) every morning and night, but haven't had time to work on it.

Maybe it's not contagious, maybe I passed it on. :wave1:

Robert
 
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