View Full Version : How do you check Spark Plug wires with Multimeter?


4U 2 NV
Jun 26th, 02, 12:14 PM
My friends engine misses at idle. The plugs look good, and the cap and rotor look good too. How do you check the wires with a multimeter to see if he has a bad wire? He had his AC Delco R45TS plugs gapped at 50 for about 4 months when the factory says 45. We did a tune up and put them back to 45, but the miss is still there. Do you think this has anything to do with the problem he's having.

69RS
Jun 26th, 02, 01:18 PM
You measure the resistance of the wire(end to end), Ohms scale on the multimeter. OL would indicate a open.

SY1
Jun 27th, 02, 05:43 AM
You can also check them with a Megger if you know anyone that has one. This will tell you at 50,000 volts if the insulation is breaking down or not. The eaiest and quickest solution is go to Auto Zone and buy a set of their lifetime wires for $15 and replace them one at a time until you find the one that is suspect. If it turns out it is the wires I'd then purchase a good set of the manufacturer you choose.

Dave

phel69
Jun 29th, 02, 02:10 AM
Pull off one wire at a time until you find one that makes no difference in the miss at idle. Then you know where to start.

------------------
Bob
Garnet Red 69/SS396/TH400/355 Posi
94 HD Dyna Wideglide

dgrewhl
Jun 30th, 02, 05:02 AM
<BLOCKQUOTE>quote:</font><HR>Originally posted by 4U 2 NV:
My friends engine misses at idle. The plugs look good, and the cap and rotor look good too. How do you check the wires with a multimeter to see if he has a bad wire? He had his AC Delco R45TS plugs gapped at 50 for about 4 months when the factory says 45. We did a tune up and put them back to 45, but the miss is still there. Do you think this has anything to do with the problem he's having.<HR></BLOCKQUOTE>

If a plug looks wetter than most thats about the only way I know of that the plug itself is questionable...As far as a wire going bad the quickest way for me is to use a timing light on it,,,if it has a steady strobe then it should be ok,,,try and check it as close to the plug as you can,,,and have someone watch the timing wires/leads to prevent them from finding their way into the fan.
http://www.camaros.net/forum/eek.gif
..g'luck!

rodsters
Jun 30th, 02, 10:22 PM
I just had a similar instance on my 68. I changed the wires because I had planned on doing it anyways, and the car still didn't run properly. I used my multimeter to troubleshoot and found a dead spot on the bottom of my HEI coil. The center button on the coil had corroded/rusted, and apparently I was getting an inconsistent spark through it. I cleaned this off, and my problem went away.

Dobek
Jul 1st, 02, 06:11 PM
I move the pickup clip on my timing light from wire to wire and make sure I am getting a good sharp blink and consistant blinking - beats the heck out of removing plug wires at a time.

Steve