Finally got my silver disco back up and running yesterday. After about 20 minutes of idling in the driveway and around the house with no leaks or other issues, I decided to drive it ~3 miles or so to where my buddy works since i knew he was just getting off. Did great getting there and then it just died while idling when we were talking. Noticed the ground strap was loose so tightened that and then it would crank but no start. Also had P1668 immobilizer code. Cleared that code but it killed my jump box and the battery was super dead from how long it has sat so we went back to my house and got the battery out of my blue disco. Put the battery in and it started right up. Drove it home and it died again right in front of my house. Thought the positive terminal felt a little loose so I tightened it but once again, crank no start. I got my roommate to pull me into the driveway with his truck and tried to troubleshoot. I had another P1668 code, but I believe that had to do with the super dead battery and the loose ground strap and terminal. Tried key in the door locking and unlocking 3x, tried pressing inertia switch, all that, but nothing. After a while it just cranked up no problem. Some rover guys I know said that its 99% the crank position sensor since it dies after getting up to temp and then retsrtarts no problem after it cools off. I'm trying to get it going for a trip this Friday so I don't have the time to wait for a CPS so I am going to swap the one on my parts trucks and pray that that one is good. Before I load the parts canon, though, does anyone have any differing opinions on what's going on here? Thanks.

TLDR: Dies when hot, restarts when cold. Bad CPS?



You can literally see my driveway in this picture. My roommate was cracking up that it got so close yet so far

 

I would agree with the 99%. It’s a pretty classic CKPS type of failure.

 

Here's your third if you need it.

 

I just had similiar issues on my 2004 4.6.

Drive to somewhere for couple of hours.
Stop to eat for 15 min or so, starts nice, drive to next stop 15 min or so, and no longer starts.
Turns over and all like normal, but just no starting.

No error codes related to the sensor, just load of misfire, detoriated cat, bad lambda etc codes, that were there already, I still need to tackle.

Eventually it just started like normal but at somepoint driving home quite soon after I left it jerked quite bad, I mean it was like I was driving head on over a curb at 50mph.. And nothing else after that.

It did the no start a couple more times and that jerk once. Never did it die while driving.

I replaced the crank position sensor and haven't had the issue so far for over a week now. (WHY did I just write this!)

Not really a big job to replace it, it's just in really akward spot and having huge hands really did not help me at all.

 

I'm a little cautious to say I have fixed the issue, since I have only driven the truck ~ 20 miles at a time (currently doing diff break in procedure) however after swapping the CKPS out of my parts truck, along with the cover, it seems to be okay. I have done 3 20 mile drives so far since I replaced the sensor earlier today, and it has given me zero issues. I am still a little worried since I haven't gotten to drive it a long distance yet, but I guess Friday will be trial by fire.

The old cover was absolutely trashed. When feeling for the bolts I pushed my finger straight through it. The whole front face of it was just a melted pile of oily fiberglass goop. I guessing that let in enough heat to kill the CKPS, or maybe the old sensor was good but the bad cover was allowing it to get too hot and fail? Not totally sure, but would love to hear from someone who knows more about this than me. Here's what the old one looked like.


The one off the parts truck also has some signs of similar deterioration, but definitely is in much better shape. I'm keeping the old one just in case this one dies full stop, since at least that one works when cold. When I put the new engine in this summer, I am definitely going to try and add some sort of heat shield to keep this one from getting as bad as the old one.

 

Maybe form a piece of aluminum foil over it in the mean time.