1990 560SEC Spark Plug Spec?

[Mikesmerc]

Does anyone know the correct Bosch plug type for my 560.I just replaced my Bosch plugs(which I dumped without taking note of type) for Champion which doesnt seem to suit as she runs poorly (lumpy) I gapped the champion plugs but didnt improve things.
Regards
Mike

 

[talbir]

Hi there,

Only use Bosch W7-DC.

Gap them at 0.045" (1.1mm) for a smoother idle - the 560's like a bigger gap.

Whatever you do don't use platinum plugs - only MB engine they are reccomended for is the 190E Cosworth.

Champion and NGK are not that great.

 

[Mikesmerc]

Cheers Talbir.

 

[Mikesmerc]

Just bought a set of Bosch W7 DC O. Does the 'O' make a difference ?

Regards
Mike

 

[talbir]

Hi Mike,

The 'O' has no meaning.

W - specifies the gap. W specifices Wide gap of 0.036" - however, I would suggest 0.045" for the 560SEC.


7 - specifies the heat range, which Bosch define from 2-11. Some people use WR9DC in the 560 - not good for the pistons

D - specifies thread reach of 3/4"

C - specifies Copper Core Center electrode


cheers

 

[Mikesmerc]

Thanks again Talbir, shes running alot smoother now. I will never again buy Champion. This morning she started showing symptoms of her previous poor starting problem which I posted weeks ago. I havent been driving it the last few weeks but intend to from now on, but I have to depend on it starting regularly. If I booked it in to a main dealer for a diagnostic should this tell me the fault even though it seems to be an intermittent fault.
Looking at previous posts someone suggested that it may be the fuel pump relay or overvoltage relay, anyone know where these are located and any test I could preform on these?
Thanks
Mike