How to check spark plug wire simply

[cliffq]

Anybody have a simple (non-damaging) way to test the spark plug wires and/or boot without have to get access to the other end near the coils (want to avoid removing the plenum)?

Thanks,

Cliff

[Dr.Hess]

The simple way I always check spark plug wires is to take a screwdriver with a good plastic handle and put an aligator clip lead on it with the other end of the wire grounded. Then move the metal part of the screwdriver touching along the wires while the motor is running. If the lead is bad, the spark will jump to the screwdriver (which is why you hold the plastic handle and don't touch the metal part).

Dr.Hess

[teigan]

i wish i'd thought of that when testing my cables. i invited some friends over and we took turns daring eachother to lick the wires.

[cliffq]

Thanks Dr. Hess. I'll try that on the wires that are exposed. What about checking the wiring within the boot? Will it hurt the engine to pull the lead out check the voltage with a voltmeter?

[GreenV8S]

cliffq said:

Will it hurt the engine to pull the lead out check the voltage with a voltmeter?

Well you won't get a voltage unless you have the engine running, in which case your meter is going to get really pi55ed off at having 50kV shoved down it! You also need to be carefull not to damage the wire as you pull it off, easy to get 'maintenance induced failure' doing this sort of investigation.

[Dr.Hess]

Something else you can do is (with everything turned off) disconnect both ends of a lead and check the resistance with your Ohm meter. All 4 leads should be about the same. That is, if one is 2 meg ohm and the rest are 0 ohms, or vice versa, or all are 2 meg ohm except 1 that is open, etc., then you have a problem.

Dr.Hess

[GreenV8S]

That'll pick up problems where the conductor has been damaged but not the more common problems of the insulation breaking down under high tension.

[Dr.Hess]

Yeah, I know. The first test with the grounded screwdriver will pick up the more common bad insulator. And yeah, unless you have a 100KV-ish volt meter (which exist but are not in most people's toolbox or at Wal*Mart), measureing the voltage will just fry your meter.

Dr.Hess

[cliffq]

Thanks for your suggestions. Tried the screwdriver approach and nothing. Looks like I will do the ohmmeter test on both ends of the wire.

[TimRdLotus]

My two cents. The wires are routed very close to a major heat source. So if the wire is over 5 years old, and you suspect something might be wrong, then just replace it.

It's only about 40 dollars US and easy to do. The resistance test and spark test is fine, but it doesn't assure that the wires are not braking down internally and causing a missfire under load.

To replace it, you do not have to remove the plenum. Just tape a string to one of the old wires before you pull them out from the plenum area and use the string to pull the new wires through. Works like a champ. Also, I put a heat sock on the wires behind the turbo and added additional heat barrier on the shield.

[Dr.Hess]

What kind of problem are you having?

Dr.Hess

[robert87hci]

If this post is still alive {last post in August} another trick is to spray water on the wires with a squirt bottle. If a wire is leaking the water will make it short to ground. The plus side to this method is you don't get shocked... been there. Licking a leaking spark plug wire would be a great stunt for Jackass!

Cheers,
Robert