ziegler.1289

My problem originally was to fix my blower from only coming out defrost and stumbled upon a hose that is blacked off, and a code for evap leak. So I followed the hose back to the evap canister by the gas tank. It has one line going to tank, one line running up the purge solenoid, and this third one that us blocked off (first pic). Most Cherokee diagrams for this show they have a leak detection pump and filter and that this third line should run there. But I noticed their is no LDP in the passenger side firewall area or filter like in some pictures I have seen. I then looked at my evap diagram on firewall (pic), and it doesn't show I should have a LDP. I thought all 4.0 HO has LDP but my specific diagram says otherwise. The diagram does show the third house with a line over the end maybe suggesting it should be plugged. If so then why? Does anyone have a setup like this and will this have something to do with why I only have defrost? I have checked all vacuum lines and reservoir under bumper no leaks.

The one picture with the yellow text is what I thought mine should look like and realized I dont have any of that stuff. So did the previous owner rig something up or is it supposed to be this way? The actual photo of the diagram is mine and the digital copy shows a different setup with a LDP that as far as I read is the only setup. Cant find anything one mine. Couldn't get pictures to load so go to the link. Thanks in advance.

http://s1269.photobucket.com/albums/...gler1289/Jeep/

Radi

I don't know why you don't have a LDP, but even so it shouldn't affect your HVAC controls unless the purge valve is trashed and allowing all your vacuum to leak away. The engine would run poorly if that were the case.
The HVAC controls run off of a different manifold tap. Does your cruise control work?

CCKen

LDP's were introduced in 1998. Not all XJ's came from the factory with the LDP system. It may been for the California Jeeps.

My '99 is set up like yours with the LDP vent hose capped off at that same location.

ziegler.1289

I am unsure if the cruise control works, I litterally just got this Jeep and I have four BALD tires on it and currently it doesn't want to keep running without holding gas down. I am going to clean throttle body and IAC hopefully that will help that situation and get decent tires on it then I will be able to see if cruise works. Maybe if I get it to keep running this afternoon I will zip it down the road real quick, the tires are terrible though. If the purge valve was bad where would it be leaking from and is there a way of knowing? I know many people on these threads have solved their defrost only problem by numerous different solutions. Wherever I pull a vacuum line off you can hear the pressure coming out. I havnt actually inspected the vacuum reservoir but I looked down in there and its connects, and when I disconnect that hose up by the battery I hear the pressure so I assume the reservoir isnt cracked. I also heard someone simply changed their heater controls in dash and it fixed their problem. Wish someone could compile all the different fixes people have came across to make a solid thread on it.

ziegler.1289

Well thanks alot this is just what I was looking for. Just knowing my xj is not alone makes me feel better. If there is no LDP i wonder if my computer differs from a Jeep that does have that system? You would think if someone removed their LDP they would get a CEL code but I do not. Vice versa I doubt I would be able to install the LDP system and hook that hose up if I really wanted to. Seems like a good system to have to check for leaks. I really am stumped as to why they would run that line all the way from the evap canister by gas tank just to cap it off under hood. Why not just cap it at the canister? Maybe they did this so one could "upgrade" and add in the LDP?

CCKen

There are a few things on the XJ's that were put in at assembly even though the build sheet didn't call for the entire system to be installed. Wiring is one that comes to mind (and of course the LDP vent hose). My '99 has the harness in the engine bay for the Daytime Running Lights Module, but the rest of the components aren't there. I'm sure that if I looked hard enough I could find other components installed for incomplete systems.

I think I will hook up the rest of the passenger ejection seat system....

mike8301

Correct. California emission vehicles were equipped with the LDP and four O2 sensors. When I bought my XJ from an american in italy intending to bring it back stateside, it was throwing codes. Long story short the PCM had been changed and fitted with one for a CA emission vehicle where as mine was a federal emission vehicle.

I would just run a pressure check, it should be around 1 PSI for the evap system.

ziegler.1289

Yeah I noticed that the other day when I was running new wires to all the speakers and realized I have the stock amp hookups running but only have the four speaker system without tweeters. You would think they would be in business to make more money and not lose it by halfway installing stuff when they didnt need to at all. I can just imagine the assembly line, "Oh woops this one isnt suppose that have that.....Ill just rip it out."

CCKen

Somewhere along the way, I think the concept adopted by Chrysler was that it would be less expensive, labor wise, to build standardized wiring harnesses then add the neccessary components to the vehicle on the assembly line to to complete a build request .

After NAFTA was put in place (Jan 1 94) Chrysler had the wiring harnesses (and other electrical components) manufactured in Mexico. When working for Chrysler I recall some quality problems with the harnesses coming out of Mexico. Can't remember the year but it finally got worked out.