I have a Jaguar XJ6 300 4 litre Sport. I broke down the other day and the breakdown guy checked everything. He then disconnected each coil wire individually and there was no change when the coil wire was removed from cylinder 6. He noticed there was a misfire on cylinder 6 because he noticed that the engine did not change when the coil wire was removed. He checked the spark plug and coil which was fine. He then checked the ecu when he noticed the wire colour coded for that cylinder was damaged and the wire coating had come off. The wire still appeared to be intact. He put some insulation tape on the damged wire. He then checked if the wire was ok by doing a electrical test on both ends it was fine. He even ran a wire from the damged wire direct to the coil on cylinder 6 but still no pulse. He then changed the ecu over because I have a spare due to buying one for a problem that it did not rectify before. This did not work. I started the car today it started and ran with a misfire then it cut out. Now it does not start it just keeps trying to turn over. I wondered if anyone had any ideas regarding this problem as im at a dead end.

 

Someone with a scope can solve this in minutes. Without, you are severely hampered. The circuit, put simply, is the same 12 volts positive two groups of 3 coils coil, then the other side of each coil is grounded through the ECU. make sure the coil in question has 12 volts continuous positive on ones side to ground. then measure the other side voltage to ground.