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Old 05-14-2002, 10:04 PM
Registered User
Join Date: Jan 2002
Posts: 177
Plug wire resistance variance?

Greetings forum members,

Can anyone tell me what, if any, is the permissable spark plug wire resistance variance.
I just checked the plug wires on my 1972 350sl, m117 engine, and the resistances ranged from 6.05 ohms to 6.36 ohms.
Is this acceptable?
As posted earlier I have an engine shutter between 1300 & 1500 rpms.
My ideal plug resistance is 6 ohms, 1 ohm at the cap and 5 ohms at the plug.
Could this variance be responsible for the shutter?
The trigger points have been ruled out as the problem.
The shutter occurs with them disconnected.
The engine is almost running premo thanks to this forum.
I am very thankful for all the assistance.
I just came off a 250 mile trip from Boston to central Jersey and averaged 16 plus miles per gallon which included a fair amount of stop and go traffic.
The owner's manual rates the car for 17 mpg @ 68 mph.
Highway/City mpg = 17/11 mpg

72 350SL #69
73 450SL Parts Car?
78 450sl Parts Car
79 450SLC - Sold
1985 280sl
87 190E 2.6 - Donated
90 300E-Junked
97 E420
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Old 05-15-2002, 01:42 AM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
I think you should have the replaceable resistor ends. They should be 5K ohms and the wires themselves maybe 1K???. The resistor ends unscrew from the plug wire, carefully roll the boot back and unscrew the resistor end, then check the ends and wires again. Be sure to wiggle the wires while testing for intermittent fluctuations. That is providing you still have original style wires/ends.

BTW: Nice mileage figures. I'm happy to touch on 16MPG @75-80 in the 4.5.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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Old 05-15-2002, 02:02 AM
hill's Avatar
Registered User
Join Date: Feb 2001
Location: Northern Calif Sacramento
Posts: 736

I get 1K ohms on factory wires with the metal RF shields.
Happy Benzing
Darryl, Hill
2005 SL55 AMG Kleemanized
1984 500 SEC
1967 W113 California Coupe
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