UK Newbie at Wits End '98 XJ 4.0 HELP!!

After 7 faultless years with a 97 XJ Sport that died, got a stunning 98 4.0 XJ with only 70K. It runs of petrol (as we say here) and lpg. Ran perfect on lpg but rough on petrol. Changed injectors, throttle body, all sensors, lamda on exhaust, not only was it no better, the dash then failed and gearbox went into limp mode.
Have subsequently replaced gearbox solenoids, gearbox control unit, . We then took it to a Jeep main dealer for diagnostics ,turns out the ECU was not original but they set it up with their kit, still no good, the nub of it is the the ecu and gearbox aren't communicating , on the dash the orange key light is on and the speedo and rev don't work. To cap it all last night all the electrics died. It is far too good to scrap. Anyone got any ideas? I'd be really grateful !!!1

you say all the electrics died, as in nothing when you turn the key?

the chrysler style ignition switches fail like that.
as to your no bus issues.
The cluster connectors are notorious for needing cleaned and the pins re tensioned.
The rest of it could be a no power situation to the TCM, or something along the lines has failed/shorted and is taking out the bus.

87manche said:

you say all the electrics died, as in nothing when you turn the key?

the chrysler style ignition switches fail like that.
as to your no bus issues.
The cluster connectors are notorious for needing cleaned and the pins re tensioned.
The rest of it could be a no power situation to the TCM, or something along the lines has failed/shorted and is taking out the bus.

Click to expand...

thank you so much for the quick response, I need as many ideas as possible as we are running out of ideas, we'll add these to the mix! Ironically my earlier jeep did 7 years heavy work with just needing a water pump and a radiator so this is a bit mind blowing.....

Greets; Ran Petrol, and LPG in 1972--'74 into a VW Van. My converter was from England, and it allowed me to draw vapor from the top of the propane tank, i.e., the 'straw' did not go to the bottom bringing forth liquid towards a more typical LPG 'liquid' going to a heat exchanger before introduction into the carb system. Switching over, and running on Petrol was fine.., until one day it's manual 'switching-valve' got contaminated with some sludge from the Petrol Tank. As an aside, I suppose you are running LPG to a heat exchanger, and not drawing pure gas vapor into you fuel rail. SO; Check out that Petrol valve in make sure it's working correctly, i.e., allowing full fuel flow of Petrol. If your valve is mechanical.., easy fix to clean. If it is electrically operated then that might be testable.

Have fun!

also, check the junction block in the passenger side footwell.

sometimes they get wet from the antenna grommet just above, get corroded and do strange things.

Thanks guys, keep it coming, I'm hoping my jeep man will join in the discussion, he's techie, I'm not, I'm just a passionate jeep steering wheel attendant.............

Right,

As Pete has said, the jeep first went into a non jeep person for rough running which wasn't resolved.
From there it came to me with no auto gears (limp mode), a test revealed failed gearbox solenoid so all were replaced, this led to failed dash as in no rpm and speedo. The SKIS light had been illuminated throughout as has the airbag light.


Wiring harness checked and appears ok, TCM operational, PCM operational, no issues with water ingress in foot wells.


Dash has been removed and cleaned and all connections ok but there wasn't a strong continuous signal from the crank sensor so I replaced that as well. All gears and dash worked until the jeep was next turned off.


After a restart it was back to square one.


The jeep was then driven to top up with lpg, where it wouldn't switch over to lpg and cut out. After 3 restarts it went dead, no power to anything, like the battery was removed from the jeep.


I've got it back on a trailer but not looked again yet.




We did take it to local jeep dealer but they reported that there was no communication between gearbox, pcm and TCM. They also stated the Ecu wasn't the factory one but it has been working in the jeep previously.


My fear is major Ecu failure

Google for ECU numbers compatible with your year XJ, or consult the dealer for them.., no fear.., just some pounds, shipping, etc. It's a good idea to be prepared for EMP by having a spare ECU wrapped up in the manner of a Farraday Cage. Just another 2 pennies.

Could it be that the non stock, (incorrect), ECU unit in your XJ was utilized because it could accommodate the LPG system tied in? I'll defer to others to figure that one out.

Hi guys, The saga continues..........everything electrical in the car is working perfectly except the cluster,I have tried another cluster and no difference so the original cluster is OK, fuel, temp , oil gauges work , only warning light on now is airbag ( whereas before immobiiser was on too and the immob works fine) but rev and speedo don't work!. Any input would be greatly appreciated, I shall not be giving up.....

Also do you know if a clock spring off a non cruise will work on this one which has cruise, I never use it here ...its too crowded...all the vehicles are too close together!!
This is just in case the airbag light is due to that, not just a glitch, I can get one off my scrapped 97

See Pic Below....because she's worth it...

Try this... These guys deal with. This issue all the time.

http://www.ausjeepoffroad.com/forum/showthread.php?t=143004