It looks like F8DC4 plugs are NLA from Mercedes and they have superceded to 003 159 68 03 when I tried to order 003 159 67 03. I just got the plugs today and they look like the OEM branded F8DC4 plugs I'm used to with the blue Mercedes markings, except they say "Made in France" with the part number 14F-8 DU4 stamped on them.

Anyone know if these are resistorless copper plugs and are equivalent to F8DC4, not FR8DC4?

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I have found a very good and cheap substitute for the discontinued copper core plugs. Autolite makes a copper core 104BP that I picked up for less than $1.25 each and they are running great in my 92 300TE. I know they aren't on the official list, but they are the correct heat range, all other specs match identically and they are definitely copper core.

Simply ohm the tip to electrode to make sure it is not a R plug.

Best F8DC4 replacement for 104 Waste Spark Ign [ DIS] systems is NGK BCP6ES.

Copper core/non resistor.

https://www.summitracing.com/parts/ngk-4930

90% of fouled plugs/skips/misfires on 104 waste spark systems is caused by the Resistor boots on top of the plug, not the plug . Good idea to change these 3 boots whenever changing the plugs on 104's ................

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A Dalton

This is exactly what I have in my M104.980:

Spark PLug (Beru 14F-8 DU4): A0031596803

RayH

Thanks for the tips. I measured resistance across the spark plug body and looks like there's no resistor in here:

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my 99 m104 only likes champions.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt