87 2.5 vs 4.0 Renix Computer?

[Nate C]

Is this the Renix computer? I'm getting ready to put the 4.0 in (previously a 2.5) are the computers the same?

I'm worried it won't fire the injectors correctly.

 

 

[Pete M]

90 and earlier are Renix. The 2.5 has one injector, the 4.0 has 6. No, it likely won't work. :D The real question is, will the rest of your dash harness work with the 4.0? :dunno:

[Automan2164]

:popcorn:

 

Rob L.

[Eagle]

That's the computer, but you need to change it for one from a 4.0L. Don't remember for sure, but I believe the 4.0L has more wires and more pins, so you probably will need to change the entire harness between the engine and the computer. After all, the 4.0L has to fire six injectors, the 2.5L only has one.

[comanchedude]

My current MJ was a 2wd 4cy stick that I converted to 4.0 4x4 auto. you have to use a 4.0 computer and the dash wire harness works just as it is no problem. you do have to replace the harness from the fire wall side from the 4.0 MJ. so when you pull the 4.0 computer also get the engine compartment. now I used the parts from a MJ so I don't know that a XJ would work as far as the wire harness.

[mjeff87]

X2 on what comanchedude said.....interior harness is plug and play so long as you stay Renix, but you'll need the underhood harness and ECU from a 4.0L. XJ/MJ harness is the same (but if you do an inteior harness swap, they are slightly different).

 

Try to use a later model underhood harness to eliminate the craptastic C100 connector on the firewall.

 

Jeff

[Nate C]

Awesome info thanks guys. :cheers: Both trucks are 87's and using the Renix system. So according to Comanchedude I'm all set on the dash harness :clapping: I really don't want to tear into that dash if I don't have to. So I pulled the 2.5's computer and harness out as you said. As you can see in the background I purchased some beer to appease the Manche Gods here on the forum.

 

 

I'll yank the one out of the donor within the next few days and put it in.

 

 

 

How about all of this stuff? :hmm: The wire harness I pulled was connected to these, I think they're relays

and maybe ignition coil? :dunno: then it goes on to another harness that hits all the front light stuff and continues

around the engine compartment and back in through the firewall into the fuse panel.

[aemsee]

Not clear about the last question? Are you asking if you have to hook that stuff back up?

[mjeff87]

yes, you have to swap the entire underhood harness, from the bulkhead connector thru the header panel (you can leave the headlight subharness, just disconnect it) and back to the ECU. The whole mess seperates into two pieces around the relay center via a bunch of connectors. To get the first section of harness out (the one that goes thru the header panel), disconnect everything at the relay center and pull the short section of harness back thur the hole in the header panel beside the headlight cutout on the passenger side and then back thru the header panel cutout on the driverside. Then unplug the bulkhead connector (there's a 1/4 bolt in the center that you have to loosen, and it's a PITA) and pull the whole mess up and out. The bulkhead connectors will not fit thru the cutout in the header panel.

 

Jeff