I am in the middle of the swap.

I got my engine from a 99 Grand Cherokee auto, and I got the complete wiring harness/computer from the same engine. The engine looks super clean, but from what I have been reading it may be difficult to get through the OBDII splicing.

From the junkyard I had him send me a pre 95 fuel regulator which is external and mounted on the rail. I am going to run an external fuel pump from a ford truck and my original CJ gas tank with an return line into the tank.

My question: Will this work with the OBDII system? or do I have to do something else??

What is the deal with the gauges? Can I use my original gauges?

I went by my local jeep dealership and tried looking up the wiring diagram in the WJ book for 99 for the bulkhead connector, but we couldn't find the big diagram? Can anyone send me the diagram?

Any additional help would be greatly appreciated.
Thanks

Charlie
combres@sandiego.edu

I see no reason your fuel pump setup wouldn't work as long as you've got sufficient pressure. (I'm guessing 40-60 lbs.)

You really should get a FSM for the 99 GC. It will answer your fuel pump requirement and bulkhead connector questions and help you immeasurably during the swap...

You're probably going to have to fool the evaporative emissions and catalytic converter crap to get it to work. Never done this myself, but I've heard it can be a bitch. Again, an FSM would help here. There are probably writeps on line about how to accomplish this as well. I suggest using Google.

The gauges all run off a bus. If you were swapping into a TJ it'd be easy (same bus architecture), but since you're not, you're kinda stuck. Since I'd guess the computer needs the inputs from the existing senders, you'll probably need to drill and tap for new senders and run a separate set of mechanical or electrical senders for your gauges. (at least O.P. and Temperature anyhow)

Good luck, HTH,
Jake

Actually, I found out yesterday that my engine is from a 99 Cherokee, which I am not sure if it makes a difference since the gauges are probably the same.

I found this out putting the water pump in, the gap is difference on a GC than on a cherokee, so I need an water pump off an older model wrangler. My salvage guy was telling me something different.

Are you sure the gauges are digital off this XJ computer?

And why would i have to fool the emissions system. I have the full exhaust off of the Cherokee with both o2 sensors before and aft the cat. The salvage yard I got the engine from, put in pre 96 injectors so that the fuel system would work with the external fuel regulator, I got the rail off of a 95 wrangler.

I think that if I match up the original CJ wires off of the bulkhead connector with the new bulkhead connector, and just ground the neutral safety switch, everything should be fine. I could be wrong though.

Does anyone have a similar setup that has done this before that can provide me with some tips or a walkthrough of the wiring?
Thanks
Charlie

So you're talking 4.0 H.O. inline-6. That's a horse of a different color. My gut says yeah, they probably have the serial bus gauges since the TJs came out in '97 and have the same 4.0 engine. It could be that they never 'upgraded' :rolleyes: the Cherokees to the bus though...

As far as using the existing senders goes, if the gauges run off a bus, there is no connection from the sender to the bulkhead. I think the senders feed straight to the computer and then the signal travels from the computer, through the bulkhead, to the gauges, as a digital signal via the bus.

I suppose IF the senders are "regular" type senders that send a signal that would be meaningful to some gauge or other, a guy could probably splice into the lines at the senders and run it to a gauge. (Might mess up the reading that the computer gets thoough... not sure.) As for whether the senders give any sort of reading the would be meaningful to some gauge or other, I have no idea. Could be they're the same senders that came on earlier non-bus computer versions of the 4.0, maybe they're something wacky and in that case you'd need separate senders. (really not THAT big a deal--you're just talking about two holes...)

You should be O.K. on emissions if you got all the O2 sensors and crap from the donor.

You might try NAXJA for Cherokee-specific info.


Jake