Testing A Sparkplug wire.
Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Testing A Sparkplug wire.
I think I may have a sparkplug wire not delivering like it should. I have access to one of them Digital Multimeter thingies, but don't know much about it.
Can one of yous guys give me play by play instructions on how to set up the meter and how to test the wire.
FYI: It is a Mallory Pro Sidewinder 8MM Silicone Suppression, if that makes any difference.
thanks
John
Can one of yous guys give me play by play instructions on how to set up the meter and how to test the wire.
FYI: It is a Mallory Pro Sidewinder 8MM Silicone Suppression, if that makes any difference.
thanks
John
Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
Sorry John, I do not know much about those meters, but what I do when looking at spark plug wires is use my inductive timing light, just put it on the wires one at a time and watch the light to see how it is firing. Kind of seat of the pants way of doing it.
Cargo Master
Joined: Jul 2006
Posts: 3,014
Likes: 91
From: Concord, CA
I believe the key to it is how much resistance there is. So the meter should be setfor "ohms" and then measure from one end to the other. Measure all of them to see if the one in question has greater resistance than the others or not. Conventional wires have 10,000-15,000 ohms per foot of length. More than that would be defective.
If you suspect a wire is bad then you can also run the engine in the dark in order to look and listen. Do you hear crackle or see little electrical sparks. If not sure then spray some fresh water on the spark plug boot in question and see waht happens. Or use a well grounded screwdriver (jumper cable) with a well insluated handle and run the tip of the screwdriver along the wire top to bottom. If there is a leak you will see an arc.
If you suspect a wire is bad then you can also run the engine in the dark in order to look and listen. Do you hear crackle or see little electrical sparks. If not sure then spray some fresh water on the spark plug boot in question and see waht happens. Or use a well grounded screwdriver (jumper cable) with a well insluated handle and run the tip of the screwdriver along the wire top to bottom. If there is a leak you will see an arc.
Lead Driver
Joined: Jun 2006
Posts: 5,635
Likes: 963
From: Near Yosemite CA
I think it should be 0 ohms end to end, you dont want the spark to encounter any resistance getting to the plug. Most DVMs (digital volt meters) are auto sensing, so you should be able to set it to ohms and put your leads on each end, then also wiggle the wire, some breaks/cracks are good until you wiggle them. Also check your plugs, I have had a few plugs that had cracked ceramics, and you couldn't tell until it was dark like tbm3 said.
Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
1st report
OK, The battery was down in my multimeter, and now with a new one I have to report.
1st I set it to OHMS audio, there is a 1 on the screen, I touch the probe tips and it alarms. I touch the spark plug wire and no tone.
I move it to 2000 and I have a 1 on the screen. With a fairly new 7MM wire the 1 remains, connect to the suspect 8MM wire and the reading goes to 722/725 with wiggle.
Replaced the plugs yesterday.
Feedback please.
John
1st I set it to OHMS audio, there is a 1 on the screen, I touch the probe tips and it alarms. I touch the spark plug wire and no tone.
I move it to 2000 and I have a 1 on the screen. With a fairly new 7MM wire the 1 remains, connect to the suspect 8MM wire and the reading goes to 722/725 with wiggle.
Replaced the plugs yesterday.
Feedback please.
John
Cargo Master
Joined: Jul 2006
Posts: 3,014
Likes: 91
From: Concord, CA
Do a search regarding spark plug wire resistance and you will see what I talk about. Also will see there can be danger to a cars electronic systems when the wire has no resistance, not to mention a hell of a lot of radio interference with such wires.
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Well a good performance wire should measure 300-350ohms per foot.
Here are some really good wires.http://www.performancedistributors.com/livewire.htm
Here are some really good wires.http://www.performancedistributors.com/livewire.htm
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
This is giving me a head ache. Don't laugh but I am trying to run a 220 V system on 110, and am suffering with brownout conditions. The lights are on but nobody is at home. sigh
John
John
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Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
John,
This may sound ****, but Hi Per wires don't Generally last very long on street engines as they break down with use. The More use they get the more they break down etc.
NASCAR runs a set 500 miles and chux it for a new one. In the Drag car we run them about 100 passes and replace them.
I usually reccommend to folks to go get a good set of OEM or NAPA-Belden Street wires & run a street rated IGN set up. I use a Duraspark Blue Struck OEM system with the NAPA Wires that have Magnetic suppression capabilities. They last around 3-4 yrs, while the others only seem last several months at the most. Especially if they sit after having been used for a while.
I also note the total resistance before I install the wires, average that for all 8 cyls & use that as a guide or baseline number when I'm diagnosing Ign system later, . . . . FWIW man.
CIAO FBp
This may sound ****, but Hi Per wires don't Generally last very long on street engines as they break down with use. The More use they get the more they break down etc.
NASCAR runs a set 500 miles and chux it for a new one. In the Drag car we run them about 100 passes and replace them.
I usually reccommend to folks to go get a good set of OEM or NAPA-Belden Street wires & run a street rated IGN set up. I use a Duraspark Blue Struck OEM system with the NAPA Wires that have Magnetic suppression capabilities. They last around 3-4 yrs, while the others only seem last several months at the most. Especially if they sit after having been used for a while.
I also note the total resistance before I install the wires, average that for all 8 cyls & use that as a guide or baseline number when I'm diagnosing Ign system later, . . . . FWIW man.
CIAO FBp
Posting Guru
Joined: Dec 2000
Posts: 1,793
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From: San Diego CA
John at 725 ohms the wire conductor is fine but the insulation may have broken down and is leaking. Use the grounded screwdriver test or swap the wire with a known good wire. Make sure all other tune-up specs are set. A marginal wire will fire at idle and miss at higher rpm.
Elder User
Joined: May 2005
Posts: 581
Likes: 1
From: Montana
Am i safe to assume from reading the posts that a set of wires are only good for three to four years. maybe thats part of the problem with my 300 - 6 in the 4wd, theyv'e been in there for over 15 years. the truck doesn't get run all that much so does the rule still stand for age. ???? dutch
Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Well fellow truck owners, I don't have the coins today like I did when I purchased the Unilite distributer, and Promaster coil, but I got them on the truck along with the Pro Sidewinder wires.
I will have to purchase a less expensive set of wires. Should I go with 7MM, 8MM or what size wires? Don't have 30,000 miles on the current set over at least a 5 year period, but I would like a good wire recommendation.
Thanks for your advice,
John
I will have to purchase a less expensive set of wires. Should I go with 7MM, 8MM or what size wires? Don't have 30,000 miles on the current set over at least a 5 year period, but I would like a good wire recommendation.
Thanks for your advice,
John
Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Thanks Rich, Does this part number look right? Item#: BEL700142 That is NAPA 7MM wires for $32.49
I'll check at the NAPA store later.
Other than size what differences are between the 7MM & 8MM wire sets?
John
I'll check at the NAPA store later.
Other than size what differences are between the 7MM & 8MM wire sets?
John