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  #1  
Old January 17th, 2019, 17:41
benXJ benXJ is offline
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98 Cherokee 4.0 elec connectors

Haven't been on here in a while (Sold my last XJ)
But I took the engine and trans (4.0/AX15), to go into my CJ8

I need some insight on some electrical connectors as I put it all back together.

These are all on the passenger side, and are part of the distributor and the alternator. Can someone get pics or trace the wires from these connectors? One of the pics is the large black/white wire off the back of the alternator. Does that connect to the PDC?

Oh, and the vacuum connection at the rear of the valve cover. Can I just put a filter there? Did that connect to the factory air box?

Thanks









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  #2  
Old January 19th, 2019, 10:17
lawsoncl lawsoncl is offline
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Re: 98 Cherokee 4.0 elec connectors

You're transplanting the original wiring harness too? Almost all the connectors are keyed, so it's hard to misplug anything. If you have an FSM you can trace out where wires are supposed to go. The breather on the rear of the valve cover went to the intake manifold so it gets vacuum, and the front went to the air box for fresh air.
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  #3  
Old January 20th, 2019, 08:27
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

Yes, I have (fairly certain) the entire wiring harness from the XJ, and between the FSM and the keyed connectors, I have most of it.

I just want/need confirmation of how the PDC is wired (both a wire from the battery and the wire from the alternator on the single stud on the PDC?)

I've located all the connectors but can't seem to find the connector to the distributor. I also didn't see the distributor wiring connection in the FSM. If I knew where it ran and the color of the connector (most likely black), I might could figure out what was going on .

Thanks
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  #4  
Old January 22nd, 2019, 17:42
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

Figured it out. The grey connector, right beside the camshaft connector in the first pic.....that's it.

It was right in my face.
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  #5  
Old March 11th, 2019, 05:52
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

So I got my engine to fire up.

I have a question though...I kind of hacked my wiring harness and was thinking about starting from scratch again (lots of lessons learned) but don't know what years/models/options harnesses will work.

I'm currently using a 1998 engine/manual trans (ax15) and the wiring harness and computer from that vehicle.

Will a harness from an automatic XJ work with my M/T computer? Would I need to get an Auto computer too? What about TJ harness? Those are easier to find with manual trans. I know I'd need a distributor harness version.

Thanks
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  #6  
Old March 11th, 2019, 08:54
lawsoncl lawsoncl is offline
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Re: 98 Cherokee 4.0 elec connectors

I think the automatic harness would just have the extra connectors for the trans computer, and it's associated wiring, which you can just leave unhooked. Only difference I could see would be a minor modification to connect the neutral or clutch switch so you can crank the starter, and hokking up the reverse lights.
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  #7  
Old March 11th, 2019, 16:00
RCP Phx RCP Phx is offline
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Re: 98 Cherokee 4.0 elec connectors

Can't speak for your 98 but 2k was very harness specific.
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  #8  
Old March 11th, 2019, 20:29
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

yea...I'd have to stick with the distributor version (up to 99?) the later ones have a coil pack setup I believe.
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  #9  
Old May 2nd, 2019, 09:21
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

SHENANIGANS

So i'm back to work on this CJ/4.0 swap. It was running great, i've let it idle for a few hours over the past weeks to check over everything and for leaks. Nothing was odd. I had an appt at the exhaust shop this morning.

Well, I had just recently changed the oil, so I cranked it up last night to make sure all was good before it's maiden voyage. It fired right up. However after about 5 mins, I noticed it sounding different, a very slight miss was evident. Then I noticed my radio turned off. So while it was still running, I checked the voltage at the battery. 10 volts. That explains it. So I cut it off. I then hooked jumper cables to the jeep and cranked it back up. Getting 11.5 volts at the battery and 11.8 coming off the big wire at the alternator. No good. So I check all wires and grounds (nothing had been touched and the vehicle hadn't been driven since the last time it ran, and all was OK then) and everything looks and feels OK.

So I replace the alternator, and the same things happen. 11.8 V at the alt output and the battery slowly drains itself while running. Revving the engine makes no difference at the alt. output.

I have a 1998 4.0 and ECU and all wiring and 'overnight' something went bad. Well, truth be told, I never checked to make sure it was charging normally, but all seemed OK during the hours of idling over the past few weeks.

Did some reading online and saw a method of grounding one of the smaller studs on the back of the alt to bypass the voltage regulator function of the ECU. I did this and saw the volts jump up to 16.5 on my meter and fall right back down to 11.5 with the ground removed. I can see the volts dropping on the meter as it's idling. I believe this is telling me the alt is OK and to suspect the computer? Does that sound reasonable?

I've also swapped in a known good battery and the same things happen....low voltage output of the alt, measured at the larger single wire on the back of the alt.

Thanks
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  #10  
Old May 2nd, 2019, 09:23
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

and is there a way to bypass the ECU voltage regulator or add an external regulator?

Any other tests to do?

thanks
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  #11  
Old May 2nd, 2019, 10:41
alwayzAMC alwayzAMC is offline
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Re: 98 Cherokee 4.0 elec connectors

shot in the dark, but did you install the battery temp sensor with your swap? iirc the charging system is dependant on battery temp to change voltage to the battery, not sure but may be a spot to start to look into
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  #12  
Old May 2nd, 2019, 11:34
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

I did not install it (or splice in a resistor)...I am going to do that just because it's easy and to get rid of the code, but from my reading on the subject, it only reduces the voltage by a few tenths over the whole range. I'm seeing below 12 V out of the alt to begin with, where it should be close to 14. So 11 Vs. 11.3 volts would not make a difference to me.

But I am going to do splice in a resistor to fool it, just haven't done it yet.

Thanks
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  #13  
Old May 5th, 2019, 09:42
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

spliced in a 10K resistor into the battery temp switch wiring. i THINK it made a small difference in output, but am still getting right at 12V out of the alternator. Seeing 11.8V or so at the battery and slowly drops while engine is running. This allows it to run for about 2-3 minutes before the battery voltage drops to about 10V and the engine starts to misfire.

Anyone dealt with this? I read all the forums about the voltage regulator and opinions are all over the place. Some say that computer circuit never fails, while the next person has had to deal with it numerous times.

Thanks
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  #14  
Old May 6th, 2019, 07:50
benXJ benXJ is offline
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Re: 98 Cherokee 4.0 elec connectors

well, sorry for the bother. I was looking over the wiring again to figure out how to wire in an external voltage regulator, and noticed that one of the wires controlling the alt. output from the computer was not connected. Hooked that up and all is well. Alt. is outputting 14.03 volts at idle now.

Thanks again.
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