died when temps high, why ?

[dan89XJ]

89 XJ 4.0L

Well, it was weird.. I was driving down the freeway with engien operating at 210 F, got stuck in some slow moving traffic and it was a hot day 95 derees, engien op temp rose to 235 dergees, and started to stumble - so I pulled over and the Jeep died. I tried to start it back up - crank crank crank - wouldnt fire. So I sat for like 15 min and the temp needle went below 210 and I tried to start it again, and she fired ! I was off again.

So, why did it die like that ? started back up after it cooled off some ?

After diagonosing my cooling system, I found I have a plugged radiator

 

[skierbri10]

YEah, I think there is a sensor that goes to the computer that shuts of the engine or something. Either that or the temps caused a problem with the fuel air mixture.

 

[XJXJ]

I don't believe Renix has high-temp cutoff and mine's been pretty hot before I found the radiator sucked. Maybe the CPS and/or connector flaked-out when it got HOT? Or, perhaps the cam position sensor? Any number of things might not like getting that hot under hood.

My CPS connector used to quit at weird times on my '89. Seemed kinda fragile so I just spliced the connector out of the path and hasn't been an issue since.

Since my new rad over a year ago, it's been great even in the hottest weather. Dicked around with every band-aid in the bag only to realize I should have changed the rad 5 years sooner.

 

[dan89XJ]

I am going to be looking to upgrade my radiator with a new one with a fill cap and convert to open system.

Intresting theroy about the sensors flaking out when getting hot. Maybe thats all it was.

 

[wilcharl]

i am convinced the renix does have some sort... twice ive had the temp up there and had that hapepnd.. from what limited info on the renix that exists tehre doesnt appear to be one however had it happen twice..... i dont know the mystery renix box may be smarter then we think.. i dont think it owuld shut the engine down though when runing that could be deadly but i could see it keeping u from restarting which were both my instances

 

[scoobyxj]

My guess is vapor lock. From the gass boiling in the fuel rail.

 

[8Mud]

The wifes XJ would periodically fail to restart, when it was hot, turned out to be the hard line (fuel) was a bit close to the exhaust manifold. I noticed on the newer XJ´s, portions of the fuel hard line, are wraped with insulation.
I noticed when my 88 had a flacky 02 sensor the higher the temp. the lower the idle, it would fall 300-400 RPM. I was wondering if it would eventually start to stall, but changed out the 02 sensor before things got that bad. When the motor is shut down, even at 235, the temp. keeps going up for awhile.

 

[Hawaiian Style]

There's something to that CPS theory. If the wires get hot it screws up the signal to the comp. Been there, done that. PS If you're hitting 235 you got a cooling problem. I never see the other side of 215 even with a flogging.