TwoXJS

Hey, guys. We just got a new flexplate in my brother's '89 the other day. Got it all together, test drive it and all seemed fine other then a little hesitation. Got to looking at the Crank Sensor wires and they were burned through by the exhaust, so we went out and got a replacement from Autozone today.

Put it in, started it up and it didn't run for ****! Extremely rough idle and backfires when you give it gas. Put the original back on, same problem....What could possibly cause this!? It was running good yesterday!

belvedere

not encouraging

cruiser54

Look at the photo below for wire routing.

And then go to post #7 in my link below for proper diagnosis.

TwoXJS

Alright, so we tested the one we got and it reads okay on ohms and AC voltage. We drilled the mounting holes a little bit to get it a bit closer to the flywheel and that really helped! But now, it runs good for a few miles, then starts acting up. It hardly accelerates at all, even at WOT, and seems like the engine is alternating on and off going down the road.

It'll stall out if you dont give it enough gas coming from a start as well. Not backfiring that i can hear and idles fine in park and neutral.

Slim357

Id get an oem cps if I were you. Best place is the dealership or possibly napa.

cruiser54

Sounds like it's running out of fuel.

sv41878

Test it while it's hot see if the ohms are way up could be a defective sensor

TwoXJS

We'll have to test it tomorrow, I had to do some brake repairs today to the '93. Somehow the smaller spring at the bottom between the shoes on the rear came off at some point. Then a bleeder valve snapped off, then a hard line fitting rounded off....Helluva day....

cruiser54

Better yet, test it for AC voltage when it's hot.

TwoXJS

What should the ohms and AC be reading? When we tested the AZ one we got, it was reading around .250 ohms and the highest AC I saw was .28

cruiser54

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

TwoXJS

Thanks, Cruiser! We already drilled out the holes to get it closer, but it seemed the flexplate may have been hitting it when revving then engine, not to sure. We'll test it again tomorrow and check for AC voltage. Quick question....Like I said, the highest voltage I saw was between .25 and .30 AC. It would still start, but could the low voltage cause it to run like this?

I only drove it for about ten minutes earlier today before it started acting up. Now that I think about it, it almost felt like the transmission was stuck in too high a gear, then shifting between gears going down the road. Hardly accelerates off a stop, hence stuck in high gear. When I turned around, I had to use a driveway. Backed up, put it drive and started to take off when it died. Fired right back up though!

cruiser54

Sounds as if the CPS is weak. Test it .