Hello all,

From one day to the next, albeit after an overheat of sorts (did a short drive and noticed my temp was above normal while parking. Fans didn't kick on and so she got a bit warm) my XJR won't start.

After the minor/close to overheat incident the car sat all night. Next day went to start it to fix the cooling fan problem and I get nothing. Not the slightest sign of life.

I'm thinking CKPS from what I've read. Checked the 5a fuse up front in the engine bay fuse box and moved the three relays next to the washer spray bottle around to rule out faulty relais. Though I am not certain and open to ideas.

Used brake clean down the throttle body to check for spark. Nothing. Not a hint of life. It just cranks and cranks.

Anyone know the testing procedure of the CKPS what values between which terminals I'm looking for?

Thanks in advance,

 

The XJR/6 uses the same crank sensor as the standard XJ6

Not sure about values/testing. Others will know.

Does the tachometer needle bounce a little while cranking the engine? If so, the sensor is 'probably' OK. If the tach needle remains motionless, the crank sensor is faulty.

Cheers
DD

 

tach doesn't do a thing. is it common for them to fail suddenly? If anyone does know what values I'm looking for that would be great. I'd prefer to test the component before replacing it.

Thanks

 

Good luck with that. Plenty of discussion in here somewhere on it. I believe this is the one you need an O-scope to check.

 

I ama big fan of diagnosis rather than parts replacement, but it is a darned good bet you have a bad CKPS if you have no tach bounce at cranking!
You could exclude other possibilities by checking all of the engine/ ecu related fuses and the ecu power infeed relay. The CKPS should read about 1200 ohms across the leads, as I recall. If you have a significantly different reading you canbe sure it is bad. It might or might not be OK with 1200 ohms.

 

Reminds me of my trials and tribulations with ignition coils.

The only spec provided was a primary resistance of .75 ohm

Unfortunately, meeting that spec does not guarantee a properly functioning coil, nor does being outside of that spec mean that the coil won't function perfectly well


Cheers
DD

 

These engines have coil packs. No dizzy. No seperate coil

 

Did I suggest otherwise?

Right. No distributor.

But they do have six separate coils, one for each cylinder.

Cheers
DD

 

Update:

I have replaced the Crank Position Sensor. No change. Still a no start condition.

What is interesting is that when the car first was a no start. I tried to start it several times. After a few goes it would not engage the starter any more.

When I first got the car it did the same thing. So I "hotwired" it by turning the ignition key to the ON position and using a jump lead from the positive terminal on the firewall to the white wire that goes to the starter and that worked every time.

After it ran when I got it, I looked at the gear lever housing and it wasn't regestering in P. That was that problem solved too.

Then it recently wouldn't start again. P engages fine, ligths upetc. When attempting to crank it draws no power as the voltage needle doesn't drop.

When I "hotwire" it now, still no joy. It won't fire.

What are the fuses and or relays that control the starter (and circuit). Where else can I look now that I have ruled out the Crank Position Sensor (even though my old one does NOT measure any resistance so it must be bad.

Fuses and relays I need to check?

Thanks in advance.

Feeling a bit stumped.

cheers

 

scuby,

You can download the 1995 Electrical Guide at the link below, courtesy of our forum member Gus:

http://www.jagrepair.com/images/Auto.../jagxj1995.pdf

The manual will show you all of the fuses, relays, components and connections involved in the starter circuit.

One thought that occurs to me is that since the car hasn't been running in awhile, your battery may be flat. Can you measure the voltage across the terminals before cranking and then again while trying to crank? If the voltage falls much below 11V while cranking the ECM will not trigger the ignition to fire. If you've tried to start the car unsuccessfully several times, perhaps the battery no longer has enough juice to spin the starter.

Cheers,

Don

 

I'm back. Had a lot going on. Back surgery, moving house and garage too. The old XJR is still a non runner.

I have a new CKPS in there now. Tach bounces while cranking. Still dealing with fact that it won't start on the key. P & N show up. That's another problem to solve once it runs.

Checked all the fuses and relays. Everything is fine and in one piece.

I am stumped. It will crank and crank every so often come to life smooth as silk for about a second or two. Then after that it will try and try to fire, a cylinder here, another one there, but never run.

It has kept "running" a few times but would fire 2 maybe 3 cylinders at most and was very unhappy and soon died. Lot's of vapor out the exhaust and cracked manifolds...

I've pulled and cleaned the plugs. They are were wet. As it fires here and there and every so often runs smoothly albeit very shorty, I'm going to call that good spark. CKPS in good order. Fuel pump relay operating correctly and I can hear the pump priming... wet plugs after trying to start so there's fuel. Even pinched off the return hose and it wanted to run but very very poorly. Fuel pressure? Seems strange that every so often it just fires perfectly then dies or stumbles of a few cylinders at a time and dies within 5 seconds...

What's next? I want to pull the engine to mate to my 5 speed and put it all in my series 2 jag but I won't untill it's running right first.

Please help!

thanks

 

Contaminated fuel? Water in the tank falls to the bottom and goes to the head of the queue for delivery to the engine, so a little can go a long way in terms of causing a problem.

 

I would agree with countyjag that yours problem would be very much fuel-related. To be sure, try using starting fluid to see if engine would stay running longer. If positive, empty the tank of old fuel, replace fuel filter and re-inject new fuel.

 

Will do although I'm still baffled by the occasional perfect start. I did just put 10 liters of fresh fuel in as it was low on fuel. I suppose water could have gotten in but to refresh your memories:

I had driven the car. Parked the car, tried to start it the next morning and it wouldn't fire. That was at the beginning of this thread just about, but either way it ran and then suddenly didnt'.

To be sure the ignition system is in order I'll try and keep it running on starter fluid although with the supercharger in the way it's a little tricky...

 

I have re-visited your post again. If there is water in your tank, adding fresh fuel would not help as water will get into the system to the front. See my XJR story and pictures here:
https://www.jaguarforums.com/forum/x...k-woes-174265/

If your engine has perfect starts but then dies, fuel supply is the prime suspect. Another possibility could be suffocation due to a bad MAF or clogged exhaust system. Once you have ruled out water, fuel lines and fuel pressure, you can move on to investigate electrical woes like the ECU, the BPM, wiring connections, poor contacts.