I found this with my "super reliable" AJ16 today, and thought some others may be interested.

Started with an oily mess on the a/c compressor mounting bracket, bugga, wash the front down, simple enough, YEP.

Top chain tensioner gasket leaking, simple fix, no big deal.

Then the horror, NO START, NOTHING, cranking just fine, bugga again.

No panic, have a drink, mandatory as you all know.

Looked over all I had touched, nothing obvious. Then I spied some water sitting IN the top little bit of the plug for the crank angle sensor, mmm, now this is the loom section of the plug assembly, NAH, no way this could not be the cause, but curiosity had me unplug the thing, fair dinkum, what a gooey mess in the lower bit (crank sensor plug), more words uttered.

Some carby cleaner sprayed in the 2 sections of that plug, blown dry, replugged, turned the key, INSTANT ACTION.

Drove and did what we had to do all day, NO issues.

I am now more curious of this oddity. The plug is "vertical" and any muck/water/oil/whatever gets straight onto it, and with NO engine driven fan blowing stuff away, possibly compounds the issue, dunno, still thinking on that one.

I will look tomorrow at either sealing the connections (RTV), or remounting the thing horizontal, or simply solder the 2 wires and forget the plug, now that sounds like a plan.

My rather disturbed brain is thinking, is this another reason for NO START on these cars. I mean there must be a lot of muck floating around that area over the years, and unless the sensor is changed (mine was 1 year ago) you would NEVER touch it.

Just my findings/thoughts on a COLD day downunder.

Enjoy.

 

The angle of approach might have something to with the problem since it happened after you washed off the compressor front. That angle probably does not happen in most circumstances.

The accumulated gunk also might have helped protect the connection from the elements.

Certainly, soldering the connection would be a good fix. No connector to come loose, fail, etc. If it ever needs to be separated, a pair of diagonal cutters does a fine job

There was a certain electronic ignition prone to failure in heat during the late seventies. Replacing the distributor would fix the problem ... for a few months. Snipping off the connector and soldering the wires fixed the probem permanently. The distributor replacement worked because it came with a new connector and replugging the connection cleaned the contacts. Eventually, that connector would loosen leading to yet another distributor replacement. It's always the lazy one who figures out the cure

 

Agreed.

Prior to reading this answer I have been working on the "Green One" today. Outside the square where I usually operate.

It is now dark and COLD here so I am inside, enough for the day.

I spent a few hours on this today, as I am far from convinced that washing the front should cause all that oily goo to get inside that lower section of the connector??.

My reasons for this stem back a few months when we had to traverse some deep water on a flooded road. About 6" or so deep. So SLOW was the required speed, more of a crawl. NO issues, until on drier ground and the engine would not rev, 1500rpm then nothing. Since it was running fine up to that rpm, and I was close to home, we crawled home. Let it cool down, started it again, like new, so I knew something had got wet, and had dried out. Checked all the obvious, nothing found, so let it be, but always questioning what went bugga up, and always wondering when it would happen again??.

Been sweet until this wash off of the front RH corner of the engine. Done about 10k kms since the deep water.

Looking at that plug again and I saw the problem. It is a 4 terminal plug, OK, we only use 2 terminals, so there is a whitish plastic thingy in there to fill the void of the other 2 terminals not used. OK in principle, but, that plastic thingy is NOT a sealing piece, and the open section of the unused holes are facing UP.

I dribbled oil on the top face, and then unplugged the thing, and had oil inside the lower section, AHA found it. Washed all that again with carby cleaner, and applied a blob of RTV to the 2 open slots, and 2 others I deemed could allow ingress. Basically sealed the top section totally with RTV. Replugged it. Dribbled oil again, NOTHING inside the lower section, dry as I wanted.

Some photos I took to try and assist are included, so I hope they work, and are clear, as I am NO photographer.

 

Good fix. At least you know exactly where to look if the symptom arises again.

How about stuffing the cavity with dielectric grease as a secondary measure?

 

Read my mind.

Cant find the tube I know I have in the shed, so on the shopping list it goes.

Will post back, obviously, if the fix is a dud, HAHAHA.

 

The golden rule of DIY auto repair:

"fix it like you never, ever want to touch it again ... but use anti-seize anyways"

 

I know that only tooooooo well.

Maintaining V12's imprints that in the brain very early in the process.

The X300 kind of has you forget that due its superb reliability, and the fact it DONT LEAK OIL, is just plain scary, so opening the bonnet to constantly check this and that is a non-event.

AHA, never-seize, Jaguar required diet, MUST HAVE.

 

Technically off the OP's topic, but in response to your comment about the X300 not leaking oil, I, too, find it remarkable! I bought a 17 year old car that doesn't leak oil. Impressive! Says a lot about the design, parts, and previous owners' care, at least in my case.

 

A slow oil leak is not necessarily a bad thing. It's like a self maintaining oil bath for the undercarriage. Great in snow country.

 

OK, UPDATE time.

Been out in the X300 all afternoon.

Started as usual cold, and idled as it always has, THEN, the ever annoying 20-30rpm surge as the temp gauge "just cracks" the rest position was no more, and NO, I have not had a drink, YET. This has pestered me since ownership, and all sorts of items changed/cleaned/reset, has made NO difference. As soon as the temp gauge got 1/2 way to N it went as smooth as expected.

Anyway, drove about 150kms today and the engine felt sweeter, yep I know, and more responsive, to the point the wife even commented on it, and she RARELY makes a good comment about my car (coz its not a V12).

My days of the "warm and fuzzy" after working on my car are waaaaaay gone, its a car, it runs, what else is there???.

So, I summise that my connector was indeed a tad hissy, and the contacts were not as good as they should have been, so a "fuzzy" signal was seen by the ECU's and hence the unsweet running I had believed was "normal", was in fact unsweet.

I reckon for the simple task involved, a simple unplug and clean of this connector would do no harm. Maybe some of those "dead" crank angle sensors are not so dead after all. Mine will be tested when the rain stops and I get that urge again.

 

Sorry about this Gents but I am sure that I read somewhere in the forum that the CAS or CPS is a Ford component but I cannot seem to find it again. Do any of you know where it is so that I can reference it again. My car has done 100k miles and from what I hear I can expect it to fail anytime soon. As I intend fitting one of Mike's modified brackets I thought it would be a good time to change it anyway.
Thanks in advance.
David

 

David,

My old CAS has LUCAS stamped on the rubber boot, which is surprising, as the engine management system on these is Nippon Denso?.

I looked at the time for a suitable aftermarket, and no luck, but a new book at work from Echlin, lists all sorts of CAS, and a few Toyota units look identical, and when time permits i will delve further.

The CPS is still a Lucas/Bourne as far as I know, but mine is sweet, so I have not really messed with it.

The CAS are more a failure item, as in "dead in the water" than the CPS.

 

Grant,
The engine management system used on all AJ16 engines was designed and build by Lucas. during the course of the devbelopment programme, This particular part of Lucas was bought by Sagem, so their names appears on the ECUs. Denso provided the EMS for 95MY V12 engines in X300 and XJS, and subesequent Jaguar V8 and V6 engines.

Daitheboot,
You referred to "Mike's modified bracket" in your post. Do you mean "andy's modified bracket" or do I have a competitor now?