What is the purpose of the HT lead in my car's ignition system?

Question

... and what happens if this lead is faulty?

... could it make the engine cut out as I am driving?

Answer 1

The HT leads carry the sparks from the ignition system to the spark plugs.

There is one lead for each spark plug, and 1 lead from the Ignition coil to the distributor.

If a spark plug lead was faulty you would most likely get a misfire and difficult starting.

If the coil to distributor lead was faulty the engine may well not run at all.

Over time these leads do deteriorate and I would certainly suggest them being changed every 5 years.

If you think the leads are faulty it can be interesting to open the bonnet on a dark evening and start the engine up. If you see sparks all over the place then for sure the leads are breaking down and need to be replaced.

Replacement is an easy job, buy a set of leads for your vehicle from either a dealer or from a motor factors or Halfords, replace only one lead at a time so you don't get the order mixed up.

Answer 2

Hi

An HT (High tension) lead is responsible for carrying the massive voltage required to induce an ignition spark at the spark plugs.

If your car has a distributor and a seperate coil then there will be the king HT lead from the coil to the distributor and then several HT leads from the distributor to the spark plugs.

If your vehicle has a distributor with a built in coil then there will be no king lead, just the plug leads from the distributor to the spark plugs.

If your vehicle has an indirect coil pack(s) then there will be no distributor or king lead, just the plug leads from the coil pack(s) to the spark plugs.

If you have a faulty king lead then you will get very little or no spark whatsoever at any of the plugs, and if any of the other leads are faulty then you will get very little or no spark whatsoever at the relevant spark plug, or a MISFIRE as it is more commonly known.

Cheers

Geordie

Answer 3

The HT lead is conected to the top of the spark plug. It supplies the spark plug with electricity at just the right time to make it fire and force down the piston.
There is one for each spark plug, you can easily see them on the top of the engine in most cars.
If the lead is faulty, the electricity is not getting to the spark plug and is then not firing the piston. So you dont have as much power.
If you change these yourself, make sure you take note to which lead goes to what spark plug. If you get this wrong, it wont be good for the engine.
I think thats it. ;)

Answer 4

the ht takes current from the coil or ectronic ignition unit and delivers it to the plugs alowing the car to fire. easiest way to tell if one is faulty is when it is dark, open the bonnet with the car running and you will see light flashes in the area of the lead that has failed. you would moswt likely get a misfire at lw rev's which may or may not go away when you give more engine rev's.

Answer 5

Ht Leads

Answer 6

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RE:
What is the purpose of the HT lead in my car's ignition system?
... and what happens if this lead is faulty?

Answer 7

It carries the high voltage to the spark plug. You need a high voltage to generate the spark. A faulty lead can cause misfiring or a completely dead engine (if it is the HT lead to the distributor)

Answer 8

god this goes back for me.....i may be wrong but the ht leads takes the spark from the coil to the plugs..if it is faulty you will have a weak spark...or none at all and the engine will misfire or run on 3 cylinders etc

Answer 9

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Connect them to your spark plugs and hold the free end whilst someone turns your ignition over. You will easily tell if they are working then.

Answer 10

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