Jaguar XK8 turns and won't start - no spark - Solved... kinda
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Joined: May 2018
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From: Sofia, Bulgaria
Aaand the cold start issue is still with the damn switches 
It might not be the rotary switch, but still...
The symptom now is that while cold there is a gearbox fault (p0706) and the car is in limp mode (4th gear only). Once it heats up it stops the limp mode and moves to some kind of restricted mode (no kickdown and limited acceleration, but normal gear changes) with codes p1797 and p1798. Later in the day the car would not have any restriction - to this point I haven’t checked what error codes are left then.
Soon I will replace the J gate, to eliminate it as a suspect and then if this doesn’t help we will start looking at possible harness issues between the rotary switch, j gate and tcm.
It might not be the rotary switch, but still...The symptom now is that while cold there is a gearbox fault (p0706) and the car is in limp mode (4th gear only). Once it heats up it stops the limp mode and moves to some kind of restricted mode (no kickdown and limited acceleration, but normal gear changes) with codes p1797 and p1798. Later in the day the car would not have any restriction - to this point I haven’t checked what error codes are left then.
Soon I will replace the J gate, to eliminate it as a suspect and then if this doesn’t help we will start looking at possible harness issues between the rotary switch, j gate and tcm.
Last edited by kainy; Mar 6, 2019 at 03:45 PM.
I do not think your problem is in the J Gate i would first check your shifter cable adjustment.
Link to Shifter cable adjustment http://www.jagrepair.com/images/TSB/307-01-1.pdf
Link to Shifter cable adjustment http://www.jagrepair.com/images/TSB/307-01-1.pdf
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From: Sofia, Bulgaria
I believe that was done already and I think they did it again at the dealership when they changed the rotary switch, but I will double check and to be sure will ask my mechanic to do it again per this procedure. Thanks!
Put your shifter in the manual mode to position I think #4 on your car and drive it and see if it still acts up. Not to worry the trans will up and down shift as it sees fit to do.
Gus
www.jagrepair.com
Gus
www.jagrepair.com
Understand that your “J” gate moves the transmission shifter cable on the left side of the transmission and in turn moves the linkage internal to the transmission to the left side where it moved the transmission rotary switch that sends a signal to the transmission control module that sends the information to the engine control module and the “J” gate. So in short the “J” gate is just a light telling you what gear it is in. Look at figure 5.1
Link http://jagrepair.com/images/AutoRepa.../jagxk1997.pdf
Link http://jagrepair.com/images/AutoRepa.../jagxk1997.pdf
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Joined: Mar 2019
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From: Ferrette
XK8 no light up due to fuel pump no elec
Have you tried a " Hard Reset " of the security system by removing both battery cables and putting together . This resets the system to zero state as it may have got out of sequence in your tinkering .
Pulling print for 97
http://www.jagrepair.com/images/Auto.../jagxk1997.pdf
see right side page 33 for ignition relay
The ECU provides a ground to close the relay as the control power source is from fuse # 14 / 10 amp Engine Management fuse box different then the main coil power source of fuse # 18 / 10 amp Engine Management fuse box
Pulling print for 97
http://www.jagrepair.com/images/Auto.../jagxk1997.pdf
see right side page 33 for ignition relay The ECU provides a ground to close the relay as the control power source is from fuse # 14 / 10 amp Engine Management fuse box different then the main coil power source of fuse # 18 / 10 amp Engine Management fuse box
I've tried it all. Hard ECU reset, earsing the TDCs, checked all c/b.
The starter turns, but there is no light up. When I turn the contact key, the fuel pump doesn't function (there is no voltage on the cables).
Any idea where there could be a relay or anything else?
Thanks a lot for your hints and help. Take care
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From: Sofia, Bulgaria
After 11 months of struggle I think the issue in this thread and everything linked to it is finally fixed!!!
I will try to summarise the whole process as shortly as I can
And that was it basically Biggest issue was lack of know-how of local shops. The official dealership are not of much help too, thou they were the ones to figure out the rotary switch.
At the end of the day what makes me happy is that the car is working and that my decision to buy a donor car paid off big time
Thanks to everybody for the invaluable help and support through this ordeal. I hope this was the hardest part, but this is a jag...
I will try to summarise the whole process as shortly as I can
- Not 24 hours after I bought the car it wouldn't start (but cranks)
- It was giving Engine fault error with Park/Neutral switch code
- nobody around me wanted to service a jag
- very quickly I found a work-around - as the coils didn't receive positive charge from a relay which didn't receive ground. I just gave it ground and everything was fine
- Fast forward 2 days - the engine broke down
- I changed the engine
- Fast forward 2 days - it got under 10C and the car would crank but won't start. If it was wormer it would crank
- couple of months later - issue was caused by the rotary switch on the gearbox. This was also the cause for the coils not getting power.
- During that process I changed the ECU, too
- Fast forward 2 days - again when it is under 10C the car would start but with Gearbox fault and limp mode. After it warmed up it would change to performance restricted mode and later in the it will operate fine
- The final issue was that the gearshift cable was faulty and getting stuck. I changed it along with the J-gate and the microswitches.
- In the meantime a did change the gearbox and torque converter as it was kicking on downshifting and changing the TCU didn't change anything.
And that was it basically
Biggest issue was lack of know-how of local shops. The official dealership are not of much help too, thou they were the ones to figure out the rotary switch.At the end of the day what makes me happy is that the car is working and that my decision to buy a donor car paid off big time
Thanks to everybody for the invaluable help and support through this ordeal. I hope this was the hardest part, but this is a jag...
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From: Sofia, Bulgaria
Final update!
The intermittent Gearbox Fault returned after 3 weeks, regardless of temperatures not falling under 10C (or that still may be unrelated issue )
Reason you ask? Luckily this time I found it in just couple of days. The fuse box next to the ABS was faulty, and the TCM wasn't getting power, sometimes Replaced it and everything is fine now.
The intermittent Gearbox Fault returned after 3 weeks, regardless of temperatures not falling under 10C (or that still may be unrelated issue
)Reason you ask? Luckily this time I found it in just couple of days. The fuse box next to the ABS was faulty, and the TCM wasn't getting power, sometimes
Replaced it and everything is fine now.
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From: portsmouth
Cut out
Been reading this but my problem maybe different. Car was running fine till hit big pot hole in heavy rain just managed pull over . Engine turned over ok but would not restart . AA got car back too my little workshop . No fuel pump or ign . Fitted and program another ECM now have fuel pump but no ign . Rev counter moves when cranking but if it using cam sensor and maybe crank sensor failed ? It's an aj27 engine so 4 wire twin cam sensors .
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From: portsmouth
Should be programmed ok as fuel pump working now . Am bit worried have right ECM as last letter one out . Unable find one same . Could it be single cam sensor one ? .Did send old ECM away be tested but they said unable too test it . Going start on ign side of things next.
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Should be programmed ok as fuel pump working now . Am bit worried have right ECM as last letter one out . Unable find one same . Could it be single cam sensor one ? .Did send old ECM away be tested but they said unable too test it . Going start on ign side of things next.
yes or no
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Joined: May 2015
Posts: 48
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From: portsmouth
Problem found coil relay had jumped out suspect someone not push it home correctly. Interesting it stops fuel system as well . Maybe stops fueling flooding engine when no spark . One jaguars better ideas
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