Big shock from plug wires

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
jkillelea
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 313
Joined: Mon Aug 06, 2007 2:18 pm
Location: Northport, N.Y.

Big shock from plug wires

Post by jkillelea » Wed May 16, 2018 8:00 am

Hi,
Dumb question maybe, but I was wondering if it is normal to get blasted when touching one of the spark plug wires as the engine is running. I was turning the distributor to get it at the right position and got hit. Is this a question of plug wire type, of grounding, or condenser? When I had on nitrile gloves I didn't get shocked. Any suggestions would be appreciated. Thank you all.

Ben Dover
Gee Addict
Posts: 42350
Joined: Sun Mar 02, 2008 2:37 pm
Location: Proving Ground

Re: Big shock from plug wires

Post by Ben Dover » Wed May 16, 2018 8:21 am

You were the easiest path to ground for 18,000 Volts and you are not the first nor the last to experience this.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

Bart1015
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 311
Joined: Wed Apr 16, 2014 7:20 pm
Contact:

Re: Big shock from plug wires

Post by Bart1015 » Wed May 16, 2018 9:04 am

It happens to all of us.
1942 Matching numbers GPW, capstan winch, BC-659
1945 GPW in progress
1943 Bantam trailer
1967 M151a1/M416 - Sold

Marty, SoCal
G-Lieutenant General
G-Lieutenant General
Posts: 5865
Joined: Thu Mar 09, 2006 12:34 pm

Re: Big shock from plug wires

Post by Marty, SoCal » Wed May 16, 2018 9:52 am

Probable cause is poor wire insulation.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

dpcd67
G-Lieutenant General
G-Lieutenant General
Posts: 4692
Joined: Mon Jul 25, 2011 4:41 pm
Location: Iowa

Re: Big shock from plug wires

Post by dpcd67 » Wed May 16, 2018 10:33 am

You have naturally sweaty hands, perhaps. My hands are always quite dry and it rarely happens to me.
U. S. Army 28 years.
Armor Branch


Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 3954
Joined: Sat Jan 12, 2008 7:25 am
Location: Tipton,In.

Re: Big shock from plug wires

Post by Wolfman » Thu May 17, 2018 6:38 am

Use to watch dad check the electric fence wire around the cattle lot by sticking a corn cob against it to see if it tingled.
I decided to try it.
After I got up off the ground, dad informed me, he was always sure he used a dry corn cob !
Used to watch the cows. They would stand back and very slowly stick their nose up to the wire. If the hair on their nose started to tingle, they backed off. If not, the chase was on.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 44 yrs)
EAA ( 44 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

jkillelea
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 313
Joined: Mon Aug 06, 2007 2:18 pm
Location: Northport, N.Y.

Re: Big shock from plug wires

Post by jkillelea » Thu May 17, 2018 6:56 am

So, a followup question... Does it happen to everyone ALL THE TIME? Or do I have wires that have poor insulation? Does anybody have wires with proper insulation so that they do NOT get shocked? Or do I have to check all grounding spots/connections on the engine frame and body? I do understand that my hand was the easiest path to ground for the 18000 volts. But what allowed me to be the path, wire issue or grounding issue?
Thanks,
John

User avatar
1943Willysgpw
G-Brigadier General
G-Brigadier General
Posts: 2121
Joined: Wed Sep 11, 2013 10:02 am
Location: Edmond, OK

Re: Big shock from plug wires

Post by 1943Willysgpw » Thu May 17, 2018 7:07 am

You were the path, because you were also touching the ground. (body of the vehicle). Electricity take the path of least resistance. I always wore thick rubber gloves when turning distributors because of this. I remember a time when I was working at a farm and ranch store and we regularly use a radial arm saw to cut lumber. It was shorted (safety was not a high priority back then). I would have to stand on a piece of wood to use it. My brother came to work for the summer. I did not tell him about the wood and he would get a shock. I would slide the wood out from under the table with my foot while I distracted him. I then cut the wood on the table and slid the wood on the floor back under. He would step up and ZOWWIE. Brotherly love.
"None of us are as smart as all of us"

1942 GPW 1871 DoD 2-27-42 Dallas Plant
1945 GPW 247890 DoD 1-26-45 Louisville Plant
1942 GTB 136166 DoD 9-18-42
1942 GTB 135938 DoD
1952 M100

Ben Dover
Gee Addict
Posts: 42350
Joined: Sun Mar 02, 2008 2:37 pm
Location: Proving Ground

Re: Big shock from plug wires

Post by Ben Dover » Thu May 17, 2018 11:39 am

Always expect a shock from 7MM wires . I have experienced it from new 40's 50's cars and trucks and new copper core wires on my MB.
The Water Proof wires on 24 Volt M-Series Trucks do not do that.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

Mark Jesic
G-Lieutenant Colonel
G-Lieutenant Colonel
Posts: 1169
Joined: Sun Jun 12, 2016 5:56 am
Location: Birmingham, England

Re: Big shock from plug wires

Post by Mark Jesic » Thu May 17, 2018 12:24 pm

Fully agreed with Bart, it happens to all of us. :shock: OUCH.

OldPappy
G-Sergeant First Class
G-Sergeant First Class
Posts: 93
Joined: Wed Mar 28, 2018 5:22 pm
Location: USA - East Tennessee

Re: Big shock from plug wires

Post by OldPappy » Thu May 17, 2018 12:43 pm

I hate to get shocked, and never touch spark plug wires or distributor without rubber gloves.

The reason I hate to get shocked was brought back to me by the mention of testing an electric fence with a corn cob. It made me remember a funny story from my boyhood.

Yes you can check to see if a fence is on with a corn cob, but I just wasn't that lucky. I grew up as a "city boy" but would spend the summers working on the family farm. It was a big family, and there were usually a lot of cousins my age, and older there. Being a "city boy" I got a lot of jokes pulled on me. One day, one of my older cousins told me I could check the electric fence by peeing on the wire, he said it would "sizzle".

Oh boy!, did it do that.

That particular cousin was always pulling pranks on us younger boys. We would ride horses all over the valley, and he loved to put us on spooky horses, and then spook them, things like that all the time.

I got him back later on when some of us we were playing around and decided to crawl through the open tunnel under the manger in the cattle barn. I was in front, and came upon a sleeping skunk. I knew about skunks, because I read a lot as a boy. I didn't want to be sprayed, so I grabbed the skunk by the scruff of it's neck, and it's tail, holding the tail down to prevent it from spraying me. It was struggling, hissing, and trying to bite, but gladly when I screamed for help my older cousin pulled me out from under the manger by my feet. As soon as I was out, I pretended to be terrified of the animal, and threw the skunk toward him, while I made a fast retreat.

My aunt burned his clothes, and made him bathe in tomato juice and vinegar.
A.C.Fults
East Tennessee
Shade Tree Mechanic more than 50 years.

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 3954
Joined: Sat Jan 12, 2008 7:25 am
Location: Tipton,In.

Re: Big shock from plug wires

Post by Wolfman » Thu May 17, 2018 12:44 pm

???
Does the jeep in question have solid core or carbon core wires.
Solid core wire has little to no resistance through the wire. The coil voltage builds only until there is enough to jump the plug gap.
Carbon core wires, in good shape have around 8 ohms give or take a little. The coil voltage has to build higher to over come the wire resistance as well as jump the plug spark gap.
As has been stated, electricity likes the easiest path and if that path is the person with a hand full of distributor cap. ZAP !! Especially with carbon plug wires with short boots.
Here comes another farm story. Have seen farmers, on old ignition systems, touch the bare plug connector, while on the spark plugs, to see if they were firing. :shock:
Personally, I like to short the terminal with a long bladed, plastic handled screwdriver.
You really want to be careful around modern, HEI and high tech. ignition wires. They don't just bite. They will hurt you !!
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 44 yrs)
EAA ( 44 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

OldPappy
G-Sergeant First Class
G-Sergeant First Class
Posts: 93
Joined: Wed Mar 28, 2018 5:22 pm
Location: USA - East Tennessee

Re: Big shock from plug wires

Post by OldPappy » Thu May 17, 2018 12:56 pm

I remember my grandfather sticking his finger into a light socket to see if it was hot, but I never had the desire to try that trick myself.

Sorry about the topic drift, I just couldn't resist.
A.C.Fults
East Tennessee
Shade Tree Mechanic more than 50 years.

Chuck Lutz
Gee Addict
Posts: 24066
Joined: Wed Jun 28, 2006 8:00 am
Location: Novato, CA

Re: Big shock from plug wires

Post by Chuck Lutz » Thu May 17, 2018 1:00 pm

Back in the day, we also tried to mess with things with the engine running....as I remember it, it wasn't the shock you got that hurt that you remembered, it was the pain in your elbow when it jerked back and hit the fender, radiator or other unforgiving metal. Sometimes the blood running down your arm from the gash in your elbow would serve to teach you not to do that again.

Kinda follows that old saw, "Once burned, twice shy"....

Pappy....you sure that wasn't a 12-volt light socket?
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
GPW 108552 4/17/43 Louisville, KY. USA 20371278 (DOD est./Tom W.)
Bantam T3 4582 10/29/42 USA 0173499 (est.)

User avatar
lt.luke
G-General
G-General
Posts: 9095
Joined: Fri May 09, 2003 8:56 am
Location: Oklahoma
Contact:

Re: Big shock from plug wires

Post by lt.luke » Thu May 17, 2018 1:07 pm

It does not always happen and should NOT happen. A loose connection at the terminal on the cap or broken insulation on the lines are the two common causes. Even tho it’s a lot of voltage, your nitrile gloves provided enough insulation to keep the zap in the wire where it was supposed to be.


Sent from my iPhone using Tapatalk

Post Reply

Return to “MB GPW Technical Knowledge Base”

Who is online

Users browsing this forum: Gary C V, Mark Tombleson, Vic ALLAN and 9 guests