Renix gurus needed!

[Ecomike]

Have you verified that you still have a standing 5 V at the sensor wires feeding the signal back to the ECU after grounding the sensor ground wires directly to the battery (-) post, with a "VOLT" meter, engine running?

Have you checked the sensor ground wires at the sensor with an "OHM" meter?

IF the sensors are indeed well grounded (needs to be less than 1 ohm), I would look for a ground issue at the ECU sensor ground "AT THE ECU".

If the sensor voltages now vary, like .7 to 4.7 V on the TPS from Idle to WOT, power on, engine off, I would suspect the scanner or the port wires the scanner is attached to are the problem!!!!

The port wire connections on my 87 Renix do not read properly on many of the wires anymore, that is why I do all my testing with a "MULTI Meter" (ohms and volts, LOL, how is that Old_Man????:wave1: LOL)

Renix does NOT like .2 V on the sensor ground wires, needs be a max of about .02 volts on Renix.

 

[Smash Hole]

Pulled the ECU apart. It's fried

 

[cruiser54]

Go grab one from an 89 or 90 at the JY. Auto or stick doesn't matter in your case.

 

[Ecomike]

Pulled the ECU apart. It's fried

What was fried? Pictures?

5-90 will want the old for his research if you held on to it!!!

 

[Smash Hole]

I'll have pics tonight. I got an ecu on the way and I may try repairing this one for the hell of it

 

[Smash Hole]

This diode in the center is the offender

Back side

Which I believe in turn took out the ground circuit or the other way. I don't know, I just fix em...

 

[Ecomike]

Take care that it was not a shorted wiring harness that took out the ground and or diode, before you swap ECUs? It could still be a loose wire that moves and shorts out once in a while, the worst kind to find.

ECU looks like an easy fix!

 

[Smash Hole]

Take care that it was not a shorted wiring harness that took out the ground and or diode, before you swap ECUs? It could still be a loose wire that moves and shorts out once in a while, the worst kind to find.

ECU looks like an easy fix!

I'm thinking it was when I was trying to get the damn thing started after the engine swap. It was a mess

Whoever wired this thing is an idiot. Solid house wire, wire nuts, booger solder, crimps made with a dull toothbrush, and about 10 roles of electrical tape.... There's about 7 hot wires going into the radio area, I'm surprised it hasn't burned down and took the garage with it yet.

 

[Smash Hole]

The infamous Comanche. When you type "88 Comanche wiring diagram" in google. A pic of the exact truck shows up at the top.

 

[87manche]

Take care that it was not a shorted wiring harness that took out the ground and or diode, before you swap ECUs? It could still be a loose wire that moves and shorts out once in a while, the worst kind to find.

ECU looks like an easy fix!

this.

and if you don't want the ECU I'll take it @ winterfest and repair it to keep as a spare.

 

[Smash Hole]

Got the reman in. Ran great for about two hours now it has a completely different issue.

Hydro locked motor. Throw a noid light on. ALL 6 injectors stuck open. Unplug ECU wait 5 minutes...fires up. Erratic low idle. Induced a vaccum leak and it runs/drives perfect drove it around another hour. Key off then try to restart, all 6 injectors wide open dumping fuel again. Unplug ecu, repeat, and drive I'm about done with this thing. Who has an ecu laying around that is a known good

I pulled this one apart and all looks/smells good. I can see the previous repair done to it, I'm guessing that's where my problem is this time.

On another note. Anybody run a 5 speed OBD1 HO harness/head/ecu with a standalone AW4 controller? I think that may be my winter project.

 

[cruiser54]

Had an intersting one like this at the dealership. The factory got involved. We spent 28 hours doing different things at their request.

We were wrapping the ECU in tin foil and all sorts of weird crap.

Turned out the early ECUs were not shielded well and stray electrical frequencies would cause something in the ECU to hold all 6 injectors wide open. Same as you, it would fire up after sitting and be okay for awhile.

It turned out that the cause was a bad#5 spark plug wire. It would arc momentarily and the ECU would go bonkers and fire all the injectors wide open. We put new plugs, wires, cap, and rotor on the Jeep and it was fine. We had to send back to Detroit all the replaced parts so they could duplicate the issue on another 4.0 to figure out how to shield the ECUs better.

 

[Smash Hole]

I think I heard a plug wire arcing last night. I thought it was the injector freaking out but the noid light never confirmed this.

Thank you cruiser

 

[cruiser54]

I think I heard a plug wire arcing last night. I thought it was the injector freaking out but the noid light never confirmed this.

Thank you cruiser

Let us know. This would be the second instance I've ever heard of. Just a thought. Go to a JY and get an ECU out of a 90 ending in part number 428. It's shielded properly and you'll have better throttle response and horsepower.

 

[Ecomike]

Very interesting!!!!

 

[Smash Hole]

Wires, cap, rotor, and some Roswell style tin foil action fixed that issue. Thanks again!

Now...Key on to start the engine idles around 3000 rpm. Unplug and replug tps while running all is normal. Key off and repeat. ECU is "seeing" full reference voltage this is not the case. The unplug and plug seems to fix this

I really want to try another ECU

 

[cruiser54]

Did you put the tin foil on the ECU or did you make yourself a hat with it?

Try this:
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

 

[Smash Hole]

And back to the old ECU, does anybody have a schematic for this thing? I'm a little unsure about something

 

[cruiser54]

What kind of schematic? Pinout?

 

[Smash Hole]

Did you put the tin foil on the ECU or did you make yourself a hat with it?

Try this:
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

Both, a hat and an ecu hat.

The ground circuit for the TPS tested fine on both sides, trans and engine.