Hello,

I am a new 2000 XJR owner and have experienced an intermittent starting issue three times in a month. I read through previous relevant threads, but there doesn't seem to be a consensus on what causes the issue.

The car runs faultlessly otherwise and is an astoundingly great car, but the following has happened and the car cranks and doesn't start:

-The ASC, trac, engine failsafe mode and incorrect part warning lights come on when the key is turned to the accessory position.

-The errors disappear and the car starts normally after waiting 20 minutes or so. I don't believe it's cylinder wash as this has happened after parking and restarting in an hour or two and also overnight. It only has happened when the temperature is around freezing, but it usually fires right up even below freezing. Compression is good.

-Doing a "hard reset" doesn't resolve the issue. All grounds are clean and tight, battery is newer and the voltage is 12v+ off and ~14 while running.

Any ideas are appreciated. Thank you!

 

It could be as simple as a weak battery. It needs to be right up to snuff or
funny things happen like "incorrect part fitted".

On the XJR, if the light next to PARK in the shifter is not illuminated, it will not
start. Sometimes this is caused by a loose screw. In any case, always look
at the shifter before turning the key. It can be a heart stopping moment
to crank but no start. If the light is not illuminated, just give ti a little
wiggle.

Then, start thinking fuel pumps. The symptoms are a lot like a fuel pump
starting to go.

 

Thanks for the info.

The same issue popped up again today and I read the code P1797, possibly related to various CAN connections??? I guess the next step will be to clean the ECM and TCM connectors, but if anyone has any other ideas please let me know.

 

My 01 has been doing the same. I believe it is being caused by a dirty or worn Neutral Safety Switch which is located on the right hand side of the transmission.
I would take it off, disassemble and clean it, but it is too cold for that activity right now.
As an interim step, I turned the ignition to position II with my foot on the brake so the shift lever lock disengages, and then without starting the engine, swiftly moved the shift lever through the gear positions repeatedly . This repetitive action can have the effect of cleaning the Neutral Switch's contacts, much like cleaning a mechanical TV rotary tuner(if you are old enough to remember those). The repetitive physical movement can clean the switch contacts.
I did this and so far, the symptom has not returned.
I will remove the switch and clean it this Spring.

 

Coldest night in 20 years. I'm getting a little tired of this crap.

 

Cybercg, moving through the positions seems to shorten the time needed for restart. It's now taking just a minute or two before I can start when the issue happens.

On further investigation I found that one of the two fuel pump relays is missing, so there might be some other things going on. There is still snow on the ground here so I'll let you know what I find when the weather improves!

 

I am glad that exercising the gear selector has helped you.


My intermittent start/no crank came back this morning. The car started fine, drove to a local restaurant and then upon trying to drive home, I got the 'no crank'.


My symptoms were:

• Driver door inside handle broke - I am trapped in the car now
  
  • Had to be let out using outside handle
  • This is not the core cause of the problem but added insult to injury
• Car would not crank and
  
  • Gear selector lock would not disengage when pressing brake and ignition in position II
  • Messages Engine Fail and ASC Not Avail displayed when trying to start
• Manually tripped gear selector lock and exercised gear shift. This did not resolve issue
• Tried starting in neutral…….. no go
• Waited a while and tried to start……… no go
• Exercised the brake switch by lightly depressing the brake pedal until I could hear the switch click. A bunch of times. Then tried to start……… it did. The gear selector interlock also resumed working.
• CEL now on with a P1797( CAN bus comma failure)

So, what to do? I am going to study the XJR's wiring diagrams to improve my knowledge of the design to begin with. I want to better understand the inputs needed by the ECM to allow a crank and engine start. It is raining here, recovering from snow and ice storm and since I don't have a covered work space, I am limited on what I can tackle right now.


I still suspect the Neutral Safety Switch and look forward to removing and cleaning it. It's cover is riveted on, but it will be simple to drill the rivets out, clean the switch and then reattach the cover with new rivets or screws. I may also replace the brake switch for grins, but since the car, when all is normal, will start in Park without the brake pedal depressed, I don't think that the brake switch is the cause.


I also am open to suggestions.

 

While you are messing with the switch look for solid green and yellow wires. On my XK8 they are the CAN bus circuit, and I suspect that it is the same. Make sure all the connections, especially those, are clean.

 

I might just have had an epiphany.


I have been studying the wiring diagrams and it seems that the 2001 XJR does not have a Neutral Safety Switch (Rotary Switch) located on the transmission. I only found the Rotary Switch on the NA transmission wiring diagram.


The XJR uses the Dual Linear Switch located in the console for the same purposes that the NA uses the rotary switch for.


It seems that the Body Processor Module controls whether or not the starter relay engages and it will not allow the starter relay to engage without the Dual Linear Switch being in Park or Neutral.


So, when weather permits, I will explore the possibility of cleaning or replacing the Dual Linear Switch. This symptom could also be caused by a problem with the Body Processor Module.


Nothing definite yet. Feel free to chime in.

 

Hmmh, I am confused. OKXJR says "crank, no start". But the shifter switch problem results in "no crank", right?

 

The neutral switch, based on info from the forum, can cause a no crank issue. The no crank seems to cause a P1797 code. It wasn't clear in the original post if it was a no crank issue or not, but he was getting the P1797 code.

So far, I have cleaned and checked the Ecm and TCM connectors and the linear switch connector. My next steps are to clean the Abs connectors and swap out the starter relay.

I would fully attack the problem but the temperature, snow and ice are slowing me down.

There may also be a remote possibility that the body processor is being flaky. It seems, based on the wiring diagrams, to have the last say in whether to crank and start the engine.

Any and all input is always appreciated

 

Just to clarify, I am experiencing a crank, no start condition. After waiting several minutes I can start, then the check engine light comes on (P1797).

Thanks again for the replies and ideas.

 

Removing one of the fuel pump relays is normally done for testing, or to force the
system to run on one of the pumps when the other has failed.

As a new purchase of a used car, this points to the former owner removing the
relay to get the car sold with a dead or failing pump.

The second remaining pump is now acting up.

I and others have written posts about how to verify pump operation by removing
both relays and jumping each of the relay sockets in turn. Without the engine
running, when jumpered, each of the pumps should make a whirring sound that
is clearly audible with the trunk open in a quiet environment.

But are you sure the relay is missing? There is a monitoring system that would
put up a code. Sadly, it monitors the relay coil and not the pump.

And as a new purchase, ensure that the upper tensioners have been changed
to the metal bodied tensioners. Lots of posts about that.

 

Come on. We are crossing wires here. These are two separate problems. One cranks, the other doesn't.

The tulsa car has a temperature sensor issue.

The Nashville car has a brake switch issue.

The one with the missing fuel pump relay, also has a fuel pump problem. Forgot which car that was.

I know, crabby . .

 

I'm actually glad the previous owner buggered things up a little because during the test drive it failed to fire up, putting me in a great negotiating position!

All tensioners will be done starting tomorrow and likely fuel pump(s). It's pretty obvious that the pump is (one) of the issues now as the car was sputtering a bit under acceleration today.

 

I'm with you there, Jim. When I first started looking for help here, I hitched on to old threads on a couple occasions. That's not too good a practice, but hijacking an active one is very confusing.

It's much simpler to start a new thread so that us old people don't offer thoughts that are not useful to the OP.

 

Do both. The incremental cost is nothing compared to the difficulty of accessing them.

If one goes, the other is not far behind.

In your case, one went, and the other is now on its last legs if not dead already.

 

I tend to ignore people who tag in to a thread, preferring to deal with the original post and original problem.

Resurrecting old threads gets the same reaction.

I have suggested in the past that threads be locked three months or some other such period
after the last post. Nothing worse than clicking on a post that seems active and of interest
only to find its so old that the second post was by JagTechOhio.

 

I think it needs stating that an XJR with a secondary fuel pump issue is in serious jeopardy of "lean running" which can cause a number of problems, least of which is a head gasket.

 

OK, so I finally discovered what was causing the trouble (after replacing battery, timing chain tensioners, water pump, cam sensors, checking fuel pressure etc.)

It took the Jag dealer to figure it out: the Can bus system had a communication problem because of a loose pin in the instrument pack connector! As simple as that. Now the car runs flawlessly.