I have a problem with the cruise on my 96 XJ...in that it don't work I used my vacuum gauge to check for vacuum at the T fitting on the passenger side by the battery and only found about 7 in vaccum. Pulled the vacuum canister and found a hole. Replaced it, and I now get good full engine vacuum at that t-fitting where it goes to the canister and cruise. However, cruise still doesn't work.

For what it's worth, the green light does light on the steering wheel. Any ideas what could be causing this? I heard some of the older XJ's had a little cruise control module under the dash that likes to fail spectacularly, as one poster put it lol.

Any help is always appreciated. Thanks

 

I had to replace the switch as the on/off switch would work, but the other side of switches did not. Give that a try! Pretty cheap to do too, just have to pull some crap apart to get at it.

 

put the vacuum gage in the hose that operates the cruise diaphram see if theres vac when you turn on maybe

 

there is vac there. there is no sort of solenoid or valve anywhere in the system that would cut off or apply vacuum to the cruise. what i'm willing to bet happened was the diaphragm in the cruise either went bad or there's a valve in it that allows vacuum to pull on it like in the GM version and it broke. anyone know how to test them?

 

I did some more diagnosing and figured I'd update this thread in the hopes of getting more help (and not starting another thread). I did diagnosis last night with the factory service manual, and the cruise switch, brakelight switch, and servo all check out according to the procedures in that book. Also, I have a snap-on MT2500 scanner and with that, I can activate the valves in the servo so I'm thinking the computer and wiring from it to the servo is good. Also have good vacuum to the servo.

Another possibility I am thinking is there is a wiring problem between the steering wheel and computer. But the servo switches on (you can hear it click) when I press the on button. So that makes me think maybe not lol. My Jeep has a code set for the Park/Neutral switch failure. Could this be my problem? The manual mentions nothing as far as it being involved in the cruise system. Thoughts?

 

you need to apply vacuum to the diaphram and see if it holds with a vacuum tool

 

similar to this

 

I'll hook one of those up and try it. But with the scanner hooked up, i can turn the cruise on, and it shows it as "on", but when i pres the button to set it, no valves open becuse the scanner would show them open and it doesn't.