I just wanted to pass along some maintenance stuff I did on my ignition coils today.... I hope this helps the longevity of these coils after all the discussion on this forum I would rather try to keep my OEM's to last as long has possible! As i have 134k on my original set....

1. First I tested all 6 Ignition Coils on my 1997 XJ6 L / 4.0, and all 6 tested at 1.0 resistance... which was great news.....

2. I pulled each coil out, 1 at a time.... and notice that the connections were dirty and rusty? I sprayed some carb cleaner to get it cleaned up, the wiped with some q-tips until clean..... then re-installed after i put some electrical grease inside the coil boot.

3. Last of all ... i wrapped the old coil boots with black 3M electrical tape real good and put everything back to normal.

I think it did start and idle a little bit better than before I started this project?

Hope this helps somebody to improve there idle and start up...
cheers

Jake

 

Thanks for that. I recently pulled all six OEM Lucas coils from my donor car. They were working fine and they are now individually bubble wrapped and sitting in a box inside my new "storage compartment" in the boot. I am stripping various bits and pieces from my donor car, by degrees and refurbing as I go along. This means I would have a lot of parts, sitting on a shelf, ready to swap if needed.

Things like alternator, AC pump, starter motor, ABS module etc. I also want to revamp the brake callipers with a view to doing a swap. Getting off topic, sorry.

Thanks again.

 

Great job, Jake!

Just for clarity, was the 1.0 resistance measured in ohms, milliohms, kilohms, or?

Cheers,

Don

 

The spec is .75 ohm so I suspect Jake meant '1.0 ohm resistance'.

Unfortuantely a normal(ish) primary resistance reading isn't proof positive that a coil is good.

Cheers
DD

 

Agree completely that primary resistance is not a particularly good indicator of coil performance. I have 3 coils sitting in front of me which are all faulty. Each has a dirty great crack in the coil body which causes the spark to jump to the valve cover rather than the plug. Each of the coils primary resistance is a perfect 0.75 ohm.

Also remember when measuring primary resistance, that you must measure and deduct the resistance of the voltmeter leads as they can be significant in this measurement. Just touch the two leads together, note the reading and deduct it from the measured coil resistance value.

Also I have doubts about wrapping the coil with electrical tape. I'm not sure a standard tape has the dielectric strength to handle the coil output voltage.

 

Ohms.... lucky for me that all 6 were the same.... but it did help with my cleaning even though they appeared good and running smooth?

 

I agree with your post..... i read some info a few months ago on this site. And a member wrapped his with electrical tape and he claimed it helped him? I didn't think it would hurt and might help until I can get new coils. My meter is a few years old but i tested it on the new coil i bought off ebay and it read 1.0 ohms.... so I tested the one on my good running Jag.... all 6 measured 1.0 ohms also.... i remember in your other post about the coils..... and even though it could measure right doesnt mean it would run right in the car? And then i put the new coil in my jag and it runs great sofar.... i just wanted to post some info that might help somebody.... i know you said .75 ohms was the reading..... but none of mine came out that way on my meter.... but thanks for your help and advice....
Jake

 

something to remember about coil on plug is that fresh plugs are the easiest to fire.. thus they heat the coil the least.