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XJ81 starting issue

Starbuck
Snr Member
Posts: 681
Joined: Thu Mar 19, 2015 4:48 am
Location: Melbourne, Australia

Re: XJ81 starting issue

Postby Starbuck » Thu Feb 22, 2018 9:17 pm

Hi Dave,

The specs for the gap are reasonably broad to allow for manufacturing tolerances, but they don't necessarily account for any set of combinations. Generally speaking if a shim is required it is installed at the factory and when you remove the sensor it will be there and will need to be reused. This cannot be guaranteed though depending on the supplier of the replacement sensor.

The front gap can be checked with non-metallic feeler gauges and shimmed if necessary.

The rear is a little more tricky. With the old sensor out of its bore, nudge the crank with a long extension bar and socket on the front pulley bolt until one of the teeth on the flywheel is visible, but close to one side of the bore (this is much easier with two people). I use dial verniers (a depth micrometer is specified) to measure the distance from the mounting surface to the top of the tooth. Record the measurement.

Now measure the height of the new sensor barrel and tooth, from the tip of the tooth to the mounting surface. Subtract this measurement from the first you recorded and it should be within the 0.457mm to 1.067mm specific by Jaguar. If it is less than the 0.457mm you will need to cut a shim from appropriate non-magnetic material that brings the distance within spec. I have never seen one over the 1.067mm, only ever under the 0.457mm and in both cases Jaguar had already fitted a stainless shim.

Good hunting,

Starbuck
'94 XJ12 (and other toys)

dstary
Posts: 25
Joined: Fri Feb 05, 2016 11:19 am

Re: XJ81 starting issue

Postby dstary » Tue Apr 09, 2019 2:09 am

Hello again all! It’s been a while since I have been on the site, so I thought I might provide you an update for the last six months of XJ81 motoring.

To summarise my issues, the car would occasionally fail to start (lots of cranking, fuel smell, but no spark), would sometimes start and run horribly roughly for a few seconds before the idle came up, and would sometimes be up and running and then stall (revs just plummeted to 0) a short distance from starting - when that happened, the car would always then fail to start despite lots of cranking, usually only firing into life 5-10mins later, and after that it would never stall later that trip.

The replacement extra air valve (EBC1198) was relatively easy to fit, and seemed to make the car run a little smoother once it was up to an idle, but didn’t cure long cranking while trying to start, or the odd stall.

So off the car went (late last year) to my mechanic to fit the flywheel and crankshaft position sensors (DBC12507 and DBC12508) and temperature switch/sensors. He did fit the position sensors, but didn’t get around to the temperature sensors. The car seemed cured, and was running well for a month or so before twice in a week it stalled while driving, and on another (albeit very hot) day I noticed the temperature gauge started creeping towards the red - the fuse for the cooling fans had blown, and in traffic with the A/C running there was insufficient airflow. They were fine after replacing the fuse. After this happened, I recalled the suggestions here about the passenger side fuse box, so off that went to be resoldered (it is VERY hard to find any for sale!).

The resoldering took a bit longer than I hoped, but while the fuse box was away I had more time to think about what had happened. I had had intermittent issues with two fairly minor things which I decided to live with until I got some time: the auto-dimming rear view mirror only worked sometimes, and the passenger side rear view mirror would not dip down when selecting reverse and toggling the mirror adjustment joystick down. Neither bothered me much, but as it transpires the fuses for those, and the cooling fans, are in fuse box 2 (passenger side for RHD cars). Fuse box came back, and hey presto, the mirrors now worked properly, the cooling fans have come on and off properly, but the car was still taking a bit of time to start, and sure enough, it stalled again in traffic having been running for only five minutes or so. Like the other times, this stall manifests itself with either revs dropping to 0 on coming to a stop, or hesitation at light throttle followed by revs falling to 0, and in either case, then not being able to start straight after.

Now I’m wondering how far I go with this. Do I send it in to my mechanic for weeks of methodical checking of connectors and signals to try and find something spurious? But then I had another think about it... long cranking (obviously when cold), stalling shortly into a drive (5 mins or so), then failing to start for some time, then once started didn’t stall again... it was clearly (again, as suggested here!) related to temperature. So I rummaged through the garage to find those two temperature sensors/switches (DBC12183 and DBC3729), and whacked them in.

Well since then I can report I have had no stall events, and the car fires into life quickly and regularly. So while the crank/flywheel sensors may have been suspect, I now believe that one or both of those temperature sensors was contributing to my stalling, but I clearly had fuse box issues too. For anyone experiencing similar, in order of difficulty I would recommend tackling those temperature sensors first.

All the best,

Dave
1985 XJS HE (manual conversion)
1994 Daimler Double Six (XJ81)

abercanadian
Posts: 1330
Joined: Tue Oct 16, 2012 6:50 am
Location: Vancouver Island

Re: XJ81 starting issue

Postby abercanadian » Tue Apr 09, 2019 4:33 am

Happy ending to the story - surprised though that the mirror dips when in reverse - I thought that function was eliminated on the 94's?

(Mine doesn't have it)

Larry
Image
94 XJ40 VDP vin 701729
Oyster Metallic/Doeskin on Aero Alloys
230,000 Kilometers 143,000 Miles
Daily Driver

94 XJ40 SOVEREIGN vin 703632
Diamond Blue Metallic/Barley
111,000 Kilometers/69,000 Miles
Parts Car

dstary
Posts: 25
Joined: Fri Feb 05, 2016 11:19 am

Re: XJ81 starting issue

Postby dstary » Tue Apr 09, 2019 11:25 am

Hi Larry,

I’m not sure how long the mirror dipping was around for, but it’s referred to in my owner’s handbook as being available with the seat memory function.

Image

Dave
1985 XJS HE (manual conversion)
1994 Daimler Double Six (XJ81)

rvdz
Forum Hero
Posts: 1889
Joined: Wed Jan 04, 2012 7:30 pm
Location: Southampton, Hampshire, UK

Re: XJ81 starting issue

Postby rvdz » Tue Apr 09, 2019 12:50 pm

abercanadian wrote:Happy ending to the story - surprised though that the mirror dips when in reverse - I thought that function was eliminated on the 94's?

(Mine doesn't have it)

Larry


Mine is a late '94 car and has the mirror dipping function.
Roel

1994 Sovereign 4.0 Auto [698760]

abercanadian
Posts: 1330
Joined: Tue Oct 16, 2012 6:50 am
Location: Vancouver Island

Re: XJ81 starting issue

Postby abercanadian » Tue Apr 09, 2019 3:42 pm

Lucky guys!

Although I should add I changed out the mirror on that side (right; LHD car) and installed a 91 model mirror; (had to modify wiring/plugs) however, don't remember ever having it before I swapped mirrors ..maybe only a delete on LHD cars?

Larry
Image
94 XJ40 VDP vin 701729
Oyster Metallic/Doeskin on Aero Alloys
230,000 Kilometers 143,000 Miles
Daily Driver

94 XJ40 SOVEREIGN vin 703632
Diamond Blue Metallic/Barley
111,000 Kilometers/69,000 Miles
Parts Car

pimgmx
Posts: 3336
Joined: Tue Jul 08, 2014 12:07 pm
Location: South East of the Netherlands

Re: XJ81 starting issue

Postby pimgmx » Tue Apr 09, 2019 5:36 pm

Nope: also featured on my early MY 94 (Aug 1993 iirc) LHD Sovereign...

the daily: 01 S8 http://bit.ly/2kIwP4m
the tractor: 77 LaRo LW https://bit.ly/2Hr9n6y
the eyecatcher: 93 Insignia http://bit.ly/1iGrmsU
the GT: 89 XJS http://bit.ly/1WQGpC5
the project: 95 X306 http://bit.ly/1cW11DN
the pocket rocket: 97 Z3 http://bit.ly/12IfE7B
the ex: 93 3.2 http://bit.ly/14GTNrq

naki_k
Super Moderator
Posts: 28654
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: XJ81 starting issue

Postby naki_k » Thu Apr 25, 2019 11:07 pm

dstary wrote:Hello again all! It’s been a while since I have been on the site, so I thought I might provide you an update for the last six months of XJ81 motoring.

To summarise my issues, the car would occasionally fail to start (lots of cranking, fuel smell, but no spark), would sometimes start and run horribly roughly for a few seconds before the idle came up, and would sometimes be up and running and then stall (revs just plummeted to 0) a short distance from starting - when that happened, the car would always then fail to start despite lots of cranking, usually only firing into life 5-10mins later, and after that it would never stall later that trip.

The replacement extra air valve (EBC1198) was relatively easy to fit, and seemed to make the car run a little smoother once it was up to an idle, but didn’t cure long cranking while trying to start, or the odd stall.

So off the car went (late last year) to my mechanic to fit the flywheel and crankshaft position sensors (DBC12507 and DBC12508) and temperature switch/sensors. He did fit the position sensors, but didn’t get around to the temperature sensors. The car seemed cured, and was running well for a month or so before twice in a week it stalled while driving, and on another (albeit very hot) day I noticed the temperature gauge started creeping towards the red - the fuse for the cooling fans had blown, and in traffic with the A/C running there was insufficient airflow. They were fine after replacing the fuse. After this happened, I recalled the suggestions here about the passenger side fuse box, so off that went to be resoldered (it is VERY hard to find any for sale!).

The resoldering took a bit longer than I hoped, but while the fuse box was away I had more time to think about what had happened. I had had intermittent issues with two fairly minor things which I decided to live with until I got some time: the auto-dimming rear view mirror only worked sometimes, and the passenger side rear view mirror would not dip down when selecting reverse and toggling the mirror adjustment joystick down. Neither bothered me much, but as it transpires the fuses for those, and the cooling fans, are in fuse box 2 (passenger side for RHD cars). Fuse box came back, and hey presto, the mirrors now worked properly, the cooling fans have come on and off properly, but the car was still taking a bit of time to start, and sure enough, it stalled again in traffic having been running for only five minutes or so. Like the other times, this stall manifests itself with either revs dropping to 0 on coming to a stop, or hesitation at light throttle followed by revs falling to 0, and in either case, then not being able to start straight after.

Now I’m wondering how far I go with this. Do I send it in to my mechanic for weeks of methodical checking of connectors and signals to try and find something spurious? But then I had another think about it... long cranking (obviously when cold), stalling shortly into a drive (5 mins or so), then failing to start for some time, then once started didn’t stall again... it was clearly (again, as suggested here!) related to temperature. So I rummaged through the garage to find those two temperature sensors/switches (DBC12183 and DBC3729), and whacked them in.

Well since then I can report I have had no stall events, and the car fires into life quickly and regularly. So while the crank/flywheel sensors may have been suspect, I now believe that one or both of those temperature sensors was contributing to my stalling, but I clearly had fuse box issues too. For anyone experiencing similar, in order of difficulty I would recommend tackling those temperature sensors first.

All the best,

Dave


Nice easy fixes ultimately. So often running issues can be traced back to one of the sensors/ valves. Did nothing show up on the VCM?

The fuseboxes will go or have gone on all battery in boot XJ40 sooner or later. I just did another set yesterday on one of mine.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300

dstary
Posts: 25
Joined: Fri Feb 05, 2016 11:19 am

Re: XJ81 starting issue

Postby dstary » Sun May 05, 2019 2:05 pm

Often nothing on the VCM when that happened, but sometimes I’d get a fail code. I can’t remember which it was, but at the time it was indicating a mismatch between the crank and fly position sensors. On my last stalls (after those sensors were changed) it never had a code, so I might have had simultaneous issues.

Dave
1985 XJS HE (manual conversion)
1994 Daimler Double Six (XJ81)