How to test HT leads and coil pack

wijcc

wijcc

wijcc

Soldato
Joined
10 Aug 2003
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How do you test whether your HT leads are faulty or not.. without having to buy new HT leads? Also the same with the coil pack and distributor?
I think one of my spark plugs are not working/engaging... I have changed the spark plugs to new ones with no effect.. what could be causing this?
Thanks in advance guys :).
 
Try grabbing onto the HT leads with the engine running. If you end up on your back with chest pains there's a good chance the insulation is breaking down...

HT leads are very difficult to test, substitution is usually the simplest way by far. If the car is getting on a bit chances are they are not in the best of health anyway.
 
Dogbreath said:
They only indicate the presence of some level of HT voltage at the plugs though, which there would still be unless the HT leads are virtually short circuited to ground.
Click to expand...

Yes but he was talking about distributor/coil problems as well which these could possibly highlight. I have used them many years ago (my dad got some free from the RAC who he works for) and it showed up a faulty Lumenition kit so they aren't entirely useless.

But anyway, like you I'd just buy some new leads.
 
Be careful when testing different leads & coil packs together as I know sometimes a different HT Lead set can kill a coil pack, strange as it sounds but this is something that is common on Fiesta's when using old HT leads with a new coil pack.

Not sure if this applies to other cars too??

Liam
 
Its possible to damage a coil pack if you for example have **** leads that are sparking out to ground somewhere, but simply changing the leads is unlikely to kill a coilpack.

If you are looking for it arcing out somewhere, spray a fine mist of water over the area, and it'll likely show it up. As for testing the leads/coil, there are ways to do this, but no way I'd ever recommend it to someone that has had to ask - all I will say is, keep all your testing as far away from the battery as possible.
 
You can usually spot breaking down insulation by eye.

And it is possible to kill the coil drivers with faulty/absent HT leads, if the coil drivers don't have sufficient protection. Without a HT lead, all the energy from the collapsing field goes back down the low tension side.
 
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