So, having acquired a '97 AJ16 4.0L that didn't charge...took a while but now charging ...well it was...I though it might be overcharging..at tick over the dash dial lifted to about 11v on start up ...then after a few seconds , shot up to 14v ..but wit ha few revs, climbed a little higher..never went into the red though...but obviously the dash dial might not be accurate. Was going to check it at the battery today but instead decided to take the car out for the FIRST time to actually try to enjoy it. Went for a quick circuit....coming back to the garage, a few hundred yards to go , gave her a big bootfull...( didn't look at the dash obviously so dunno if the alternator was playing a role in this ) and she took of like a scalded cat ..came to the junction ....DEAD! Completely.

Really bad dangerous place to get caught out...ran back ....got a pal to help me tow it very slowly the few hundred yard back to the garage.

Ignition comes on...turns over ....wont start ..... after cranking, there's chk engine and transmission lamp on.

I've not got a Jag code reader but stuck OBDII reader and got P0727 .. engine speed sensor no input or something ...yeah ..big help ...I know that. No other codes .

How come? .. surely before it dies it should have written a code? No crank sensor voltage, no fuel pressure... whatever ..something?

This smacks of terminal ECU failure to me...disconnecting battery and waiting an hour doesn't help. Battery is weak however, but surely that wouldn't stop it while it was running and charging?

Anyway ..unless anybody has any bright ideas of obvious places to look ( I'm obviously going back tomorrow to look for obvious hoses /; cables off.. and check ECU connectors ...where is the damned thing anyway? But ..thus far I've been pretty unimpressed by my first Jag ...it's already pretty close to going for scrap ... fed up already.

 

P0727 means that the engine stalled and the gearbox TCM did not like the sudden loss of RPM.


The DTC P0727 will always set when the engine stalls, KEY ON.


bob

 

Batteries are like tennis shoes , they don't last forever . But they play a key role in the starting sequence other then running the fuel pump and rotating the engine as it will do fine bellow the required voltage to properly power the ECU .

Rule One for a new Jaguar owner is to never put the battery in backwards as this will fry things , but is recoverable yourself to bring the car back to life . Always in the heat of battle take the time to verify the Positive post is always in the positive direction of car travel . Been there done that . A garage can also do this so be the second set of eyes to prevent them from doing it .

You can have the battery tested at the auto parts store for it's health and what you are looking for is not the charging acceptance but the load it can discharge in the starting sequence .

The health of the positive terminal as the original clamp can stretch over time and be a less then good current carrier which will drop the effective voltage . There are shims or cap looking things you place over the original battery post to give the original clamps more bite .

From my understanding you need 11.4 volts for the ECU .

There are other things after that until it reaches the engine compartment but we'll skip that for now .

Take your battery and charge or discharge the battery until you read 11.4 volts on the Right engine fuse box terminal post . with a digital volt meter verifying this value and take a piece of tape and mark the cockpit gauge that way you can monitor the forbidden zone where the engine will rotate but the ECU will not enable a light off .









Editing

 

Oh, batteries. They are so important in these cars. They have to turn over a 4.0 litre engine with 10:1 compression. Plus run all of those old-school current draining modules and NOT-LED lights. If in doubt about the health of the battery, it must be replaced. It is the starting point for proper diagnosis of all other problems. Load testing at the store is a must. But usually if you are at that point, it's probably time. It's tough to stretch the lifetime of a questionable battery. I've tried too.

Don't worry about the P0727 code. Or a P transmission code if you stall while rolling. Clear them and move on. The X300 XJ6 is first generation OBDII and is well known to not always put up codes when strange things happen. For instance, if you need new spark plugs (which you DO every 20k miles), the engine will stall occasionally at low rpm, without ever giving a code other than P0727 and possibly the trans code.

FYI the new battery you buy will most likely be larger (longer) than the one in Lady P's picture above, if it is correct for the X300. If you get one of those large beasts, you should be super good with your battery for a long time.

 

That reset button will be just an inertial switch won't it? ..a crash switch? That's unlikely to have tripped? And if it had would it not kill all dash lights and ignition, which is not the symptom I have.

Still, if it's near the ECU I need to go there presumably to look for bad connections at the ECU...where is it?

Regarding the weak battery....that wouldn't have caused the stall would it? ... If the alternator is running and and putting out 14v+ then the car should run even if the battery is a poor accumulator? .. And it's not that weak, it turned the engine over at what sounded like normal rpm for a total of probably 60seconds or so before starting to sound slow..

Are you suggesting that the with car running at high rpm, despite the alternator chucking out 14v, the LOAD on the battery will cause voltage drop at the main bus causing ECU shut down?

Basically, are you saying, 'don't despair until you've put a new battery in it' ?

What continues to baffle me is the lack of any useful codes, I'm a bit stupid on this subject. Might there be Jag 'C' codes present that my OBDII reader can't see? I always thought that manufacturer specific codes were merely an extension of OBD codes...but this is a subject I know bugger all about. I'm surprised there is nothing useful at all...P0727 might as well just say ' You've stopped pal ' ... surely the ECU must know something happened unless it had shut down ...I think I'm answereing my own question here aren't I :-)

Guy

 

SleekJag ....aye, the battery in the car is huge...I've insured things that weigh less than that!..but , it is indeed probably old and tired. I'm so broke at the moment..my other project car ( '59 Armstrong Siddeley Star Sapphire ) is bleeding me dry this month ...I'll pop down the breakers and see if I can get a big healthy battery! I suppose what confuses me is that I've never had a car before that would not continue to run despite the battery being toast as long as the alternator was doing a job of work keeping the main bus voltage up. I can't imaging a car just coming to a dead stop whilst running just 'cos the battery is tired.

I've never broken down before in a 'modern' .. it's quite disconcerting...feels like having something stolen !

also, the ABS light which was on last time the car started ( after getting it charging ) ..had gone out yesterday ... maybe this is all 'main bus voltage' related.

 

Guy,

The alternator will keep the car running unless the battery is really fried, like with dead cells or shorting. And it was cranking fine at the "no-restart" time. Sounds like something happened suddenly.

I just posted on a nearby thread about a crank but no-start where the crankshaft position sensor (CKPS) had to be replaced. That solved his problem. The car won't fire without a good one in. Look for 200 rpm on the tach while cranking. If none show, then a new CKPS is in order. They usually fail suddenly. This is a known issue and a preventive maintenance replacement item. It is on the front of the engine and reads the toothed timing wheel. Within easy reach.

The "reset" button is an inertia switch as you said. Unlikely to have tripped. I don't know if it would kill the dash lights too. The metal box filling the right side of the frame in that same photo is the ECU. The black socket (1 of 2 sockets) is visible at the top of the photo. Unplug and check sockets and pins for corrosion. A known condition more common in wet places like Edinburgh. The ECU is typically very reliable if the connectors are clean.

Don't give up on her just yet!

 

As you say ...it should run as long the battery is not completely buggered ...which it clearly isn't ...I mean it's tired and need replaced ..but after a charge up, it tests at 12v UNDER LOAD with a tester and holds it. ..so something else stopped the car running. with no codes at all to go on I don't where to start looking? Good point about the crank sensor though ...I'll spin her up on the starter and as you say the tacho should read..if it doesn't ...crank sensor is toast ..that's a good tip ..didn't think of that!

So the ECU is inside the cabin footwell.

Lady Penelope...what does 'RS3' mean in your pic?


I guess I could still be looking at a battery problem, but I've just charged it up...I'll take it down the the shed and put the tester on it...if it looks anything better than bad, and it still doesn't start, I'll check the ECU connections and the crank senser as per the tacho on cranking ..after that ...I don't think I have time for a massive diagnostic of why this car just stopped...

As I said ..I'm just baffled why there's no codes at all. .. in fact, if the crank sensor dies would that not log a code ?

When I did the timing belt on my Toyota van and forgot to plug in the crank sensor ..it wouldn't start obviously but straight away I got a 'crank sensor no value' code ..baffles me that bit!

 

It is possible that the crank sensor code means the crank sensor failed! But most likely by far it is just a symptom of the stall, the input stopped and that's why the code came up. Codes often do show up for various troubles, so your lack of them has an upside. Check out the connections at the ECU and beyond that, without any other engine codes, you are back to basics checking for spark, fuel and air.

 

When the inertia switch is triggered, the dash lights still work, so doesnt sound like that is your problem.
The fact your voltmeter went into the red could be an important clue, and I would be disinclined to dismiss it as a faulty gauge. Alternator would be high up the list of potential culprits, and excessive charging could have goosed your battery.
A good battery really is essential in these cars, and unfortunately would not be a good area to economise. Whether it is the cause of the problem is difficult to know, and may indeed be unlikely, but without one, there is a good prospect of you chasing your tail.

 

The voltmeter didn't go into the red..well not that I saw, unless it did so when I was giving it the berries! And the dash lights are on, but if the inertia switch leaves them on once triggered then that could be the problem, but I doubt it .

Why would a tripped inertia switch leave the dash lights on ..I though the whole point would be to electrically kill the car in the event of an impact ....other inertia switches I've come accross have tripped everything!

 

Trampintransit ,

In your quest to get your Jaguar up and running we're going to do some shortcuts to give you some positive results and if that resolves your drive-ability we can go back and address a area of interest with more information .

Just some information on things you have questioned before for your clarity and peace of mind .

There are some things the ECU codes will not tell you in it's design in that it was not perfect . Crankshaft position sensor is one of them that will fail in some aspects of it's use before it's complete failure . We're going to skip that for now .

The inertia switch if suspect can be bypassed by removing the connector and jumpering the 2 white wires with a paper clip .

A full 100 % battery charge is around 12.75 volts .

The ABS light is not related to the engine and will look at later as a DIY lower priority item .

The RS3 connector was for someone else when I copied the picture from another someone else and labeled it back then . In the pic for a British right hand drive you can see the gas petal .

Just for trouble shooting my opinion would be to keep the size of battery at hand but insure that it load test OK and can even swap with a good battery from another car . In service later in the cold temps then consider a A8 sized battery .

My wonderful internet was giving me problems before completing the post so let's continue :

Remove the fuel pump relay and place a heavy jumper wire in the fwd most socket in the relay socket with the use of a blade connector end . The other end of the wire you will tuck under the large post of the trunk fuse box terminal post . This will run the pump at all times bypassing the control of the pump circuit ( crankshaft position sensor related ) . If you get positive driving results we'll go back and look at that circuit later .

If you are going to have some down time I would suggest cleaning the very important ground points in the engine bay as they are just as important as the power wires to the devices and sensors in engine regulation and should be kept up just like spark plugs and oil filters .

 

 

Everybody is telling me to get a new battery, I hear that, but I just don't buy that the battery caused the stall. The alternator was charging at the moment of stall so there was 14v on the main bus, why would the ECU switch off if it's got more than the 11.5V it needs to operate? I've removed and cleaned earths in the boot ( trunk) and engine bay ( front and back ) ....on cranking, there is no movement at the tacho ..does this indicate that crank sensor is toast? ... does the crank sensor require a minimum voltage to it in order to return a signal? Is it really just coincidence that the crank sensor decides to die 3 minutes into the cars first trip out? .. I still have suspicions about over voltage at the alternator output causing damage somewhere? Anyway ...I only got ten minutes with it today, I'l be back in tomorrow but I'm going to try to borrow a big battery before spending on a battery.

I'm not saying that my battery isnt' part of the problem, but I just don't see that it was the battery that caused a car to die at speed with alternator keeping the bus voltage up? . Further, a new battery here in the UK is £132 ( $175!) ..you can see why I'm reluctant to replace a battery which is showing as good when under load on my load tester...it holds at just under 12v under load and the needle stay static. ...However, is it possible the the load tester is just not presenting ENOUGH of a load to a 100Ah battery to give a meaningful test? Is my battery tester lying to me?? Something that's only just occured to me ..is the battery that's in the car even the correct one ..it's a HSB019 100Ah 900A.

 

I had written a replay before but my unreliable WiFi lost the whole thing so I'll rewrite and send it in batches .

Good call on finding a loaner battery for troubleshooting . There are some things that were skipped in between the B +battery terminal post and the engine compartment terminal past that was covered earlier with some findings from others including Watts700 ( spelling correction needed ) . But we'll again skip that for now as your observations of voltage recovery after the start sequence and your engine stalling accrue after that in the alternator spinning phase . A professional load tester ( any parts store or shop will test for free ) will be larger then a home tester and be more accurate as 12 volts in how accurate the reading is is close to the side of badness .

Your observation on the CKPS with no gauge tack is a good point . See page 53 for a English 3.2 or 4.0 AJ16 engine :

http://www.jagrepair.com/images/Auto.../jagxj1997.pdf

The white wire should read 5.0 volts DC as the reference voltage with the key on before starting . The ECU " first power " comes though the RH engine fuse box king relay and can be tapped on all sides with a screwdriver handle to see if it floats losing power contacts or the pulling coil inside opens up with heat . You can also swap the hing relay with the LH engine fuse box . This first power goes through the troublesome Papa Indy 1 as the White / Pink wire in position 4 . This wire is shared with the coils as a power source and the ECU gives the coils a timed ground to fire off the plugs .

Editing



The CKPS is a inductance sensor that will read around 1300 ohms as a fundamental reading though sockets Red 23 to Red 26 at the ECU connector as it should be inspected . The sensor face and the sensor connector can get dirty in it' s bad environment the socket to wire crimp can get corroded so a slight tug on the wires may pull out of the crimp .




Something to note is the CKPS sensor as it starts to fail before complete failure will not enable the fuel pump relay to stay closed hence stalling the engine by fuel starvation . That is why the suggestion of easily bypassing the control and just putting power directly to the pump .

I'm going to do some other things for the next hour of two .

 

The CKPS thing wasSleekjag12's idea. Just checking, does the CKPS need a minimum voltage to return a signal?

 

5.0 is the exact reference voltage the ECU sends to the CKPS , not more not less .

Still editing above .

 

So, if there IS a voltage drop and the ECU isn't seeing the 11.4v it needs to 'switch on' then the CKPS will return no signal to the tacho? .. So...no tacho movement isn't for sure an indicator of CKPS failure...

 

Yes correct . With me not having information on what goes on inside the box you have to deduce what is going on from the outside .

 

Cheers again ...well I'm going up to the lock up tomorrow...this whole business of the tacho not moving is, it seems to me the thing to focus on? Is the CKPS itself a failure OR is not getting fed! I'm assuming that the 5v is supposed to go live with ign on without cranking? ..ie, can i test for that 5v at the CKPS connector with the engine turning over? .. that'll start to tell me something one way of another?..it does kind of point away from looking at fuel issues doesn't it.