by dave-r » 18 Apr 2001 13:21 IGNITION LEADS
The number of times I have looked under the hood of someone`s car when they have not been able to start on a cold damp morning and found the ignition leads covered in oil and dirt is incredible.
For the ignition to work properly the coil, distributor cap and ignition leads must be clean even if they are the only clean bits on the car.
Dirty leads will conduct electricity down the outside of the cable to earth. You can get a shock from touching them when that happens. Clean good quality leads are safe to touch. You can check how clean the leads are by bending back the plug boot to expose the wire insulation underneath. If you see a great difference between the colour of the exposed and protected parts - clean or replace them.
Good quality leads have the boots vulcanised to the wire so that it cannot be pulled back as this stops dirt and damp getting down there.
TESTING IGNITION LEADS
Remember this:- If a wire checks bad, it is bad. If a wire checks good, it could still be bad.
To check a wire, connect an ohm meter to each end and flex the wire back and forth while pulling over its entire length.
Another test you can do is to look at the leads in the dark.
Set the engine idle at 1,000 rpm in as dark an environment as possible. Look for sparks at the distributor cap, coil and anywhere the leads may be touching the engine. There may also be a blue corona around the leads, in which case, do not touch them!
If the wires are dark you are safe to run your fingers along them. If your fingers glow blue ( it shouldn`t hurt ) the wires are still losing a small amount of energy. This adds up to lost spark power.
Cheap wires may do this when they are new!
THINGS TO LOOK FOR WHEN BUYING NEW LEADS
1) At least 8mm diameter
2) Pure silicone insulator
3) Metal core, with spiral winding
4) Boots vulcanised to the wire if possible
5) Low impedance
Also use wire separators to prevent wires from touching each other.
The best ignition wire is the type that has a fine wire spiral wound around a ferrite or graphite impregnated core. Common trade names for these are;
SPIRAL CORE, ENERGY CORE and MAGNETIC CORE. There may be others.
These have a very low impedance but need very little radio suppression.