How To Check If A Coil Pack Is Faulty?

[swanny1970]

Hi All

 

Just wondering if anyone knows of any way to check if a coil pack is faulty? I know that misfiring is a sign, but are there any others? Driving at 70mph doesn't seem to affect the perfomance as bad as when I am driving around town at 30-40 mph. Also get a strong smell of petrol every now and again. Thanks in advance,

 

Kind regards

 

Peter

[Smilge]

Hi Peter ....... does it misfire when it's idling or only when the engine's under load? If it does misfire when it's idling, one way of checking which pack/lead is at fault is to disconnect and reconnect each lead from the spark plug in turn and listen to see if the engine running improves. When you disconnect the faulty lead and the engine appears to run smoother, even though its only running on 3, you have either a U/S lead, plug or if it appears to improve on disconnecting 2 adjacent plugs then it could be the coil pack. That's the old way of doing it anyway ...but be careful not to earth the HT lead through yourself ... it hurts!

[muffking]

The Wizards of NOS sell a HT testing gadget for a fiver. It simply plugs in to the end a HT lead and you touch the engine casing when it's turning over to see how far the spark jumps. If one sparks doesn't jump as well as the others then it has a faulty coil.

I have one of these and used it to prove a coil pack fault of 2 v6 vauxhalls where access was poor and the tool made life much easier.

[muffking]

ok, it's

[dipsomaniac]

if coil pack was faulty you would have a serious misfire and not be able to get to 70mph. i would look at plugs and leads first.

[Seatdriver]

Hi,

When the coil pack failed on my mondeo some years back the engine would idle with no apparent misfire, however once any load was put on the engine it would misfire quite badly (felt like it was running on 3) but I still could get upto 70mph no problem

 

One simple and non dangerous way to check the coil pack is to remove it. On my mondeo the underneath was potted in a white resin and there was obvious black staining of this material. When I looked closer there were very faint track lines within the compound. Purchased new coil pack from ford and hey preso 100% ok for the remainder of the time I owned the car.

 

A note on the HT system. The voltages produced by electronic ignition systems are very high and potentially fatal so be very careful messing with the leads.

 

hope this helps