V12 experts please have a look at this thread in X305 forum:
https://www.jaguarforums.com/forum/x...1/#post2352863

It's an issue with the V12 in a Daimler Double Six cutting out when hot. Newbie Antoine KIN has been told the ECU needs replacing and these are unobtainable. A beautiful car but terminal if this issue cannot be resolved.

Graham

 

Have a look at page 65 to 68 of this PDF. It will list all the comments and some of their normal values
http://www.jagrepair.com/images/Auto.../jagxj1995.pdf

I would go about this in the following way with since I dont have access to the proper pecus diag equipment

Hook up a test lamp to the fuel pump +12 lead so you can monitor it inside the cabin.

1. You need to monitor how long the fuel pump runs during / when a cut out occurs.
if the fuel pump cuts out abruptly when the stalling occurs you have an ECM power supply issue or some other fault with the fuel pump curcuit or internal/external power for the ECM.

If the engine stalls and the fuel pump continues to run for 2 seconds or more, you have a input signal supply problem to the ECM, check / clean the engine speed sensor and related wiring at the flywheel, crank positions senor at the balancer and the cam position sensor at the cam cover.


2. You want to look at your tachometer when the stalling happens
If it abruptly drops to zero you mostly likely have a signal supply problem form one of the 3 sensors listed above

If it drop slowly and seems to follow the engine speed exactly as it stalls you most likely have a fuel supplt problem, related to fuel pump, relays or injector output transistors in the ECM

The fist thing I would do is check the the three sensors, crank, engine speed and cam. The engine speed sensor on the bell housing needs to have the exact gap and the wire is routed near the exhaust manifold so it has to be checked. It hangs low too and will pickup any metal dust it can. I have fixed random stalling V12's simply by cleaning this sensor with a quick wipe with a blue shop towel. A zero dollar, fast repair.

It may be helpful to understand how coil on plug cam synch ignitions work. You have to know is that the ECM waits for a full cam rotations to find TDC then it starts counting and firing the coils soon after. If the ECM looses count for some reason like bad or unclear sensor data it will stop ignitions pulses until it a reliable re-synch can be estabolished. At low RPM (idle) this can cause a stall. On the highway at speed the engine over run gives the ECM enough time to resynch. In this case the tachometer should show a dip during the resynch process but it may be hard top notice while driving.

 

the V12 can suffer from ' fuel vapour lock ' issues, where the fuel turns to vapour in the fuel lines around the engine,

this starves the engine of fuel and causes issues like your experiencing,

just another issue to be aware of

BB

 

icasamerica and Brake buster - thanks for your input.

I've copied your replies to the OP's thread in X305 forum:
https://www.jaguarforums.com/forum/x...1/#post2353153

Please continue all further discussion of this topic there.

Graham