I’m lazy and didn’t read the entire thread; and I’m quite sure the battery topic was covered.
I know Frank is pretty much on top of this one. He’s helped me with my '86 - ignition issues.
I just finished a video about a “no start” on my '85 Series III. Put the spark back in your Jaguar to get right to it, jump to 2:28sec. I stopped at the ignition module because was the issue… I will be following up on a tune up with my next video. ANYWAY back to your hard starting.
You’re gonna need a multi-tester.
1.Battery should read somewhere between 12 & 13 volts with the ignition off. test the battery from pole to pole.
2. with the ignition on, check the voltage to the ‘+’ side of the coil (negative side to the negative on the battery), should be not less than 1 volt than the result from above. This checks the condition of the ignition circuit. If you Jag is fitted with a ballast resister, then check the resistance from one end to the other. The resistance should be between .08 & 1.0 ohms. If no ballast resister, then the voltage should read the same as step 1 above.
3. Check the condition of the primary windings on the coil. disconnect the amplifier connection from the coil, and put the test lead on the positive tester lead on the negative pole of the coil and the negative lead on the negative pole on the battary. The voltage should read the same as number 2 above. If the measured reading is 2 volts less than measured from number 2 above. then replace the coil.
4. plug the amplifier back onto the coil, using a lighted test lead. Ground 1 lead at the battery and the other lead on the negative side of the coil. Crank the engine over, the light should flicker. If not, then it’s time to replace the amplifier.
5. Ignition pick up resistance should be no less be between 2.2 and 4.8ohms. Test with the ignition off and the two amplifier leads disconnected from the coil, or disconnect the pick leads from the distributor to the the amplifier. this is your best bet to isolate the magnetic pick up. Testing from the coil is really not conclusive because it could be wire related to the ignition amplifier, the amplfier itself…
6. check the gap between the pickup should be .008-.014 in
7. The angry pixies shooting out the top of the coil should measure at no less than 25k volts and at the plug should be no less than 10k volts.
Now, the one thing I didn’t cover in my video and is glossed over here in this post is the ballast resister. What does it do? It servers 2 purposes
- regulate the voltage to the coil during starting. the biggest drain on a battery is starting. the ballast ensure consistent voltage to the ignition system to TO ADDRESS A HARD START CONDITION (I’m not yelling just emphasizing to draw your attention to this point, in case you don’t want to read the whole post.). if the voltage to the ignition drops below 10v then chances are the Jag will be a little bitch and be hard starting or leave you stranded.
- The ballast also regulates ignition system from too many volts during higher revs. Essentially keeps the ignition system safe from too many angry pixies running through it which generates heat; and we all know what heat does it cooks stuff; if it’s not edible, then it’s all bad.
Hope this helps. I also hope I didn’t just waste nearly an hour of my time because you already know it or it was already covered.
Mark