O2 sensor issues?
05-26-2019 | 06:18 AM
#121
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Posts: 2,800
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From: syracuse ny
Year: 1997
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
My2c, I haven't really followed all that you are doing here, but I see the pictures of the corrosion and would add that I found the fuseblock on the inside of my zj by the footwell to be acting up I pulled it and it looked very similar to your under the hood block in terms of corrosion. I did go to the junkyard and got another which was pristine. Took a couple hours to completely change it out. When I got the old one out it was even worse than it first looked. Cured every one of my weird body electrical issues.
So I think you were on the right path of changing it out.
So I think you were on the right path of changing it out.
05-26-2019 | 07:00 AM
#122
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
- The fuel pump is getting it's power from someplace else; or
- What you pulled out wasn't the fuel pump relay.
05-26-2019 | 07:39 AM
#123
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Can I assume all of your grounds are shiny clean? Beyond that you may have to follow those 2 jumpered lines to their point of origin to figure out why the jumper is there (which of those 2 grounds is bad). My thought is that it would have to be the Oxygen Relay Ground. It seems to me that if the fuel pump was relying on the Oxygen Relay Ground for signal, then it would shut off when the engine was in closed loop (or heater hit target temp).
This would assume that ECU is working properly, but that's the last item on the list.
This would assume that ECU is working properly, but that's the last item on the list.
05-26-2019 | 05:02 PM
#124
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Joined: Apr 2018
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From: arizona
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Correct, the ECU, like any computer does not generate power, only gives commands based on inputs.
O2 and FP relay in with jumper wire out got power with key on.
[O2 and FP relay out with jump wire in got no power with key on or off.]
[O2 relay out with jump wire in got no power with key on or off.]
[O2 relay out and jumper wire out got no power with key on or off.]
{FP relay out and jump wire out got power with key on.}
{FP relay out with jumper wire in got no power with key on.}
Either the ignition switch is bad or the ECU.
But first the relay holder needs to be verified that all the wires are either correct or not correct.
The junk yard was closed today even though they said they would be open today and tomorrow. My guess the way they run their business they'll likely will be closed tomorrow as well.
I will be getting the relay holder for verification, the ignition switch and the ECU.
It is easier to change the ECU than the ignition switch so will be trying that if the relay holder wiring is correct.
So until then this is where we or (I am).
Last edited by randy61; 05-26-2019 at 07:23 PM.
05-26-2019 | 07:12 PM
#125
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From: arizona
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I think I'm looking at the correct relays as per the 1990 FSM. There are images online that are incorrect.
Last edited by randy61; 05-26-2019 at 07:45 PM.
05-26-2019 | 07:16 PM
#126
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From: arizona
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
05-27-2019 | 05:49 AM
#127
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Great.
Negative. If O2 Relay is getting power with KEY Off, either the ignition switch is bad, or there's a splice or permanent short to provide that power. Further, we have just shown as far as the Oxygen Relay is concerned the ECU is fine.
But here's the problem with that. There are still 2 issues unaccounted for-- the switched A/C wires and how the fuel pump works without a relay but still needs the ground to work. If one of those or another yet unknown fried the ECU, and that condition is still present, you run the risk of frying the replacement issue.
The next chore will be to figure out how the fuel pump works without its relay. When you turn the key on do you hear a click anywhere? Start from the back and trace the lines forward and look for a splice.
Either the ignition switch is bad or the ECU.
It is easier to change the ECU than the ignition switch so will be trying that if the relay holder wiring is correct.
The next chore will be to figure out how the fuel pump works without its relay. When you turn the key on do you hear a click anywhere? Start from the back and trace the lines forward and look for a splice.
05-27-2019 | 06:11 AM
#128
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
05-27-2019 | 06:56 AM
#129
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
After installing the apparent good o2 sensor the ac clutch engages and have not had an issue with the ac since.
Best puzzle ever!
05-27-2019 | 09:32 PM
#130
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Joined: Apr 2018
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From: arizona
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Brown wire that shorted in the ignition switch... I see no relation ship to either the o2 or the AC. according to schematic.
05-28-2019 | 05:42 AM
#132
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
New one is 12 bucks.
Test the melted one in Off:
Test the melted one in Off:
I'm not sure if we can say that just yet, but testing the ignition switch is on Pages 8D-84 and 85 in the manual in case you don't have that already.
http://oljeep.com/parts_man/1990Jeep...viceManual.pdf
http://oljeep.com/parts_man/1990Jeep...viceManual.pdf
05-28-2019 | 06:15 AM
#134
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From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
05-28-2019 | 07:46 AM
#135
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
The burned brown wire is a sure sign of a melted switch.
You generally lose blower, radio, turn signals and something else.
If Randy is not losing those, there's a big chance the brown wire is melted to something else.
Something to do down the road is reduce the load on the brown wire. for Renix, this helps:
You generally lose blower, radio, turn signals and something else.
If Randy is not losing those, there's a big chance the brown wire is melted to something else.
Something to do down the road is reduce the load on the brown wire. for Renix, this helps:
IMPROVING BLOWER MOTOR PERFORMANCE
On 87 to 90 MJs and XJs, the blower motor’s factory grounding point is on the driver side inner fender under the sheet metal screw. This ground is shared with windshield wipers, front windshield washers, rear windshield washers, AC clutch relay, fan control relay, fog lamps, fan motor, headlamps, front turn signals, front side markers, and park lamps.
So your blower motor has its ground point 10 feet away from where it is located!!
What we’re going to do is leave that ground intact and also ground the blower motor on the passenger side inner fender much closer to the blower motor itself. This will also benefit the other components on the factory ground circuit. Take this opportunity to refresh the factory ground as a matter of course. Remove the screw, scrape the surface to bare metal and reinstall the screw securely.
Here’s what I do to get the ground much closer to the blower motor and add another ground point to this overloaded ground circuit.
Find the blower motor connector on the passenger side. Red and Black two wire connector.
Find a location where the black wire can be made to reach the passenger side inner fender, and cut the wire. You may have to do some rerouting of the harness to achieve this.
Take both cut pieces of wire and put them together into a yellow eyelet and crimp. Fasten the eyelet to a place on the passenger side inner fender with a sheet metal screw after applying OxGard to the contact surfaces. Be sure to scrape the attaching point on the fender to bare metal first.
Your blower motor will now turn faster and last longer, and the other electrical components on the circuit will benefit from a better ground path.
So your blower motor has its ground point 10 feet away from where it is located!!
What we’re going to do is leave that ground intact and also ground the blower motor on the passenger side inner fender much closer to the blower motor itself. This will also benefit the other components on the factory ground circuit. Take this opportunity to refresh the factory ground as a matter of course. Remove the screw, scrape the surface to bare metal and reinstall the screw securely.
Here’s what I do to get the ground much closer to the blower motor and add another ground point to this overloaded ground circuit.
Find the blower motor connector on the passenger side. Red and Black two wire connector.
Find a location where the black wire can be made to reach the passenger side inner fender, and cut the wire. You may have to do some rerouting of the harness to achieve this.
Take both cut pieces of wire and put them together into a yellow eyelet and crimp. Fasten the eyelet to a place on the passenger side inner fender with a sheet metal screw after applying OxGard to the contact surfaces. Be sure to scrape the attaching point on the fender to bare metal first.
Your blower motor will now turn faster and last longer, and the other electrical components on the circuit will benefit from a better ground path.
