Jaguar Repair: 85 jaguar xjs v-12, jaguar xjs, spark plug wire

Question
my car starts and then dies. somedays it runs fine. but most it starts then dies

Answer
Hi Melanie,

The fact that it starts and then dies is not enough information to diagnose what is wrong.

All engines only require 3 items to run, Compression, Fire (Ignition) and Fuel. (With conditions on each)

Compression is not going to go and come back so you can eliminate that and look toward Fire or Fuel. All failures need to be tested while in the failed mode.

This test is not hard to separate the two. Just put a timing light on the coil wire (not a spark plug wire) and tape the trigger down and start the engine.

If the flash dies first and the engine coasts to a stop then it is an ignition problem but if the engine dies and it flashes all the way till the engine stops rotating, then it is a fuel problem.

If you are not proficient on Fuel Injection you will need to get some one who is to start testing it.

Howard