I bought a Jaguar Xj6 1988 from a local auction. We went and drove the car straight home no problem at all. Drove it that day it was fine. The next morning no start. Came back to it after work and it started fine. Drove it around and it was fine. Then it did it again until it finally decided to die altogether. First I thought it was a crank sensor that was coated in oil and after doing some bench test I found online it was reading bad so I replaced it. That didn't fix the problem so I did more diagnosing of the ignition system. I was getting no spark out of the ignition coil but it was getting power on the crank. Both at the positive and negative terminal. I changed the coil and it works for a little bit and then it died again like before. I figured the module or amplifier had died so I got another one and replaced the coil again. Again the car ran and after leaving it running for a bit it died again so back to square one. I threw another coil at it and this time I added a resistor assuming that maybe it's overheating while also changing the plug wires and still it does the same thing. Not sure what to do anymore. Maybe I have things wired incorrectly and could use some help figuring this system. I usually work on modern cars and have never dealt with this before.

Thank you again for your help

 

Hi HAMSTER_OX,

Welcome to the Jaguar Forums! It's great to have you with us.

The first thing I would recommend is that you check the Vehicle Condition Monitor for any stored diagnostic trouble codes. To do so, turn the key to position II (ON) but do not crank the engine. Press and release the VCM button on the trip computer to the right of the steering wheel and watch the odometer display (the small window below the speedometer) for any message to appear. DTCs appear in the form of Fuel Fail or FF and a single-digit number, such as Fuel Fail 6 or FF8.

If you find a code, post it here and we'll try to help.

One possible cause of intermittent stalling is a small amount of water in the fuel that is getting sucked into the fuel pump intermittently. A common cause of this is a clogged drain in the rubber gaiter around the fuel filler neck. When this drain gets clogged with seeds and leaves and such, water can pool around the fuel filler neck and make its way past the fuel cap gasket and into the tank. Also, since the car was sitting for some time, you could have condensation in the tank.

A possible cause of your coil losing output is that the ECM may be disabling the ignition if the battery voltage falls much below 11 volts while cranking. I think the official voltage threshold is 10.4 volts, but most voltmeters cannot react quickly enough to measure the actual voltage sag, so if you see anything below 11 volts while cranking, suspect low battery capacity.

How does the car idle when it runs? If it idles fast or roughly, an air leak could be contributing to stalling.

Please let us know if you find a code stored in the VCM.

In the meantime, please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don