ignition capacitor
 

Hi All
On the wiring diagram I have in front of me, I see next to the coils I see an ignition capacitor with a red/white wire and a black wire to it.
I have found this on my 2003 2 litre x type, yet a jag guy tells me after checking my vin no. that it doesnt exist on my car
Can someone clarify this for me, as I have a crank no spark situation, crank sensor tested and working, power to coils, all fuses and relays checked and good.
This guy has just thrown a googly into my thoughts
Look forward to any input
Thanks in advance
John

You want that capacitor in your car. It has a very specific purpose. When your coils fire, they cause a very large electronic transient that normally shows itself as noise in the radio (what a lot refer to as alternator noise). But, this is also bad in that it causes computers to see information that they shouldn't, resulting in potential error codes. If you look at the drawings, it is connected to the same wiring as the coils. That way the noise only is in the wiring for the coils, not the whole car.

This capacitor has nothing to do with the starting of the car. It is simply there to eliminate electronic noise when the engine is running.

If you need more info, let me know.

When that capacitor fails, it can render the coils INOP.
I had a faulty capacitor 'short-to-earth' on a 3.0 S-Type once in the Jaguar shop and I finally figured out why I had NO SPARK.

I disconnected the capacitor from the circuit and the engine started!!!!!
I ordered a new one from parts and installed it. Returned the car to the customer!!!!

bob

motorcarman, I would think that if you had a bad capacitor, that it would have blown the fuse for the coils (going off of memory for the diagrams). I can see where a faulty capacitor (if shorted to earth/ground) would cause the coils not to work. But, I would expect other issues to be occurring too (ie, blown fuses).

Typically, it will just provide an AC(RF) signal path to ground, not a DC path...which will NOT blow any fuses...and since the spark signal goes to ground, no spark.


Often, they "leak" first...you'll hear that in the radio.

Thanks for all the useful replies

A quick note to let you all know where I'm at
Pulled off the capacitor and noticed that the bracket that it was mounted to was horribly bent, not impressed,
After straightening it out I also noticed that there was a scrape on the edge of the capacitor about 2mm deep where the capacitor fouled the water pump belt, again
not impressed, (the prevous owner did some strange things I think)
I then hooked up the poitive connection to battery and put a voltmeter to the earth terminal - while the unit was off the car and the voltmeter slowly dropped volts while connected to the battery, again cant work that one out
To check the crank sensor (replaced and new) the voltmeter was hooked up to the cas when the car was cranked, 2 volts evident, all good
there is no voltage on the cas plug however
My plan now is to check the ignition capacitor terminal to ground and to see of some leakage exists and to check connections to cas from the ecm
How does that sound?
Thanks again for all your input

How can I locate this capacitor in my car?
Could You help me please?
S