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Renix ECU removal procedure

M

mr_W

NAXJA Forum User
Location
Belgrade, Serbia
Hi Renix gurus!

I've run into some electric issues resulting in melted wires, and shorted out one of injectors leads. I don't know if that would cause ECM malfunction in such way that there is no spark anymore, but I would like to remove ECM and inspect it inside.

Are there any tips and tricks on how to get that damned thing out? It is tucked below the dashboard and in such position that I can barely see or feel any bolts or nuts holding it. How many of them (bolts) need to be unbolted, and which size are they?

Also, is it safe to open metal PCM case to inspect PCB inside? I mean, I won't ruin it by just opening it?

Thanks!
 
UPDATE:
I've solved no-spark issue: it was that CPS connector, after unplugging, checking with DMM, and plugging it back, it fired up instantly!

Anyway, I would still like to know how to unbolt renix ecu :)
 
Nothings easy: after breaking my back, I can see the 3 bolts. Would removing the lower dash panel make this easier? Or maybe the front seat:) wish you lived closer Cruiser54!
 
mr_W said:
UPDATE:
I've solved no-spark issue: it was that CPS connector, after unplugging, checking with DMM, and plugging it back, it fired up instantly!

Anyway, I would still like to know how to unbolt renix ecu :)
Click to expand...

Sooo, you think it's fixed forever?

Have you tested your CPS output?

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
 
mr_W said:
Hi Renix gurus!

I've run into some electric issues resulting in melted wires, and shorted out one of injectors leads. I don't know if that would cause ECM malfunction in such way that there is no spark anymore, but I would like to remove ECM and inspect it inside.

Are there any tips and tricks on how to get that damned thing out? It is tucked below the dashboard and in such position that I can barely see or feel any bolts or nuts holding it. How many of them (bolts) need to be unbolted, and which size are they?

Also, is it safe to open metal PCM case to inspect PCB inside? I mean, I won't ruin it by just opening it?

Thanks!
Click to expand...

What year? If it's an 87 or 88, click on the link in my signature and do posts 1 through 5 at a bare minimum, possibly 27. . 89 or 90, skip step 2.
 
Note from DJ
I just turned 73 on the 9th and I removed a spare from Pick a Pull for my 88’. I used 1/4 in 10mm 6 point deep socket and ratchet.

Who said retirement was easy.

I was thinking about notching the back bolt holes like the front one is if I ever have the need to install it, what are the thoughts on that idea?
 
Last edited:
djgrayxj said:
Note from DJ
I just turned 73 on the 9th and I removed a spare from Pick a Pull for my 88’. I used 1/4 in 10mm 6 point deep socket and ratchet.

Who said retirement was easy.

I was thinking about notching the back bolt holes like the front one is if I ever have the need to install it, what are the thoughts on that idea?
Click to expand...

Jeesh, I am inspired now DJ! I will tackle it this weekend. Your notching sounds like a great idea. Think I'll do also.
 
I just pulled one.

remove the lower dash valance so you can kind of see up in there.

ignore all of the bolts/nuts on the bottoms and side.

There are two nuts on studs on top. Remove those and the ECM and the bracket that it's attached to will drop out after you jam it to the passenger side. Pretty sure they were 10MM.
 
cruiser54 said:
I'll be 60 the end of this month. Think I have more flex than you? LOL.
Click to expand...

Amen to that!!

I found it fairly easy with a ratcheting box end FLAT wrench. Once I saw the bolts and got a hold on them they came right on out. I did it kneeling on my garden pad (yeah, the little green foam rubber thing :laugh: )
 
cruiser54 said:
Tell them why you're doing this, Greg.....
Click to expand...

Per one of my mentors on naxja, Cruiser54, the ECM's of 89-90 Renix Jeeps had a more aggressive ignition advance curve, resulting in a few more horse power.

I wonder if I replaced both the ECM and added the high altitude CPS, would they both combine to give more hp?
 
GregGA said:
Per one of my mentors on naxja, Cruiser54, the ECM's of 89-90 Renix Jeeps had a more aggressive ignition advance curve, resulting in a few more horse power.

I wonder if I replaced both the ECM and added the high altitude CPS, would they both combine to give more hp?
Click to expand...

Yes.

All of my Renix Jeeps have the high altitude CPS and 89 or 90 ECUs.
 
As usual, NAXJA comes through:sunshine:

Here's how I did it:

1. Drop lower dash. You can see the ECM. I went in through the opening created by dropping the dash. I used a 10mm ratcheting wrench. Hat tip Cruiser54. You have do this by feel. Same goes for the right hand or back nut.

2. Push the ECM to the left, and the two studs will come out of the bracket on the firewall, and the ECM its bracket will drop down.


3. Transfer the bracket from the old ECM to the new ECM.

4. Clean the male and female connections with electronic cleaner. Tweak the female connectors with a pick so they mske a tighter connection.

5. Reinstall on firewall bracket.

6. Replace lower dash.

It started finr, I just have to test drive it.
 
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