Any plug experts here??

[mercmadjim]

Could anybody tell me the difference between Bosch spark plugs F8DC4 and F7DCR4 please ? and if the wrong plugs were fitted could it harm the engine?
Thank you.

 

[television]

I do not know the difference, but either way you cannot harm the engine. Sparking plus usually differ in the burn temperature

 

[mercmadjim]

Sorry to doubt you Malcolm, are you sure you can't harm the engine? surely the wrong heat range plug can't do no good? as too cold a plug will not dissapate (is that how you spell it??) the heat and I am guessing the 'R' in F7DCR4 is something to do with resistance?? and if the resistance is wrong it could damage coils ?? or some other electrickery.

 

[television]

Nope you cannot hurt the car, all it means id the fuel will not be burnt as efficiently with the incorrect ones, resistor or no resistor this cannot hurt the coils or anything else. Some engines require a hot plug to get the best.

Have you tried a Google search on sparking plug and see what comes up

 

[rf065]

From t'internet..............

There are a few applications which require a gap other than the factory preset gap. If the recommended plug is not available, plugs having the same heat range but with different factory preset gaps can be substituted for each other by regapping them. Resistor plugs may be used in place of non-resistor as long as resistance value in the circuit does not exceed 15K OHMs. Do not substitute non-resistor plugs for resistor plugs. And, do not gap Bosch Platinum2 or Platinum +4 spark plugs.

Russ

 

[jibcl500]

the F7DCR4 is fitted to the twin spark mercedes engines, the F8DC4 is like a conventional plug, the F7DCR4 shouldnt be used on a single spark engine.

I could be wrong mind.

jib

 

[Jay Gee]

http://www.boschautoparts.com/Resources/FAQS/SparkPlugs.htm

Hope this link works.Lots of PDFs.7/8 is the heat range-doesn't tell you much else though. A rule of thumb I seem to remember was that 'hot' engines need cold plugs,and vice versa.

Edit. Link was in message when typed,but has disappeared on submission.I'll have another go.

 

[mercmadjim]

Yes I did the old google thing, did not learn a great lot
I had the car serviced (SLK) in Jan 09, the Indy who did the service told me the wires to my coils were hard and brittle and were likely to short out..I posted on here at the time and my neighbour who is a retired elecrical engineer checked them and said they were fine, the indy also said my rocker cover gasket was leaking oil into my plugs (which must have cured itself )because when I checked the plugs there was no oil leak.

When the car is hot it has a very slight misfire on tickover, fine when cold...the plugs that the garage fitted were F8DC4 and what should be fitted are F7DCR4....I rang MB and they said the wrong plugs were fitted and this could be the cause of my mis-fire, so I am just fishing to confirm what the chap from MB told me.
Regards
Jim.

 

[Jay Gee]

NO. Doesn't want to play. Google 'Bosch spark plug specifications',and click on the first one,titled 'Resources'

Sorry,crossed posts.(edit)

 

[mercmadjim]

the F7DCR4 is fitted to the twin spark mercedes engines, the F8DC4 is like a conventional plug, the F7DCR4 shouldnt be used on a single spark engine.

I could be wrong mind.

jib

I have a single plug head, is that what you mean by twin spark?? and the sticker under the bonnet shows the plugs should be F7DCR4 !!!

 

[mercmadjim]

NO. Doesn't want to play. Google 'Bosch spark plug specifications',and click on the first one,titled 'Resources'

Sorry,crossed posts.(edit)

Thanks for that Jay Gee.

 

[television]

The resistive plugs are more to do with the interference that can be caused by fitting the wrong ones,ie non resistive in circuits designed for resistive

 

[mercmadjim]

Thanks Malcolm, I still think it's bad for a garage to fit the wrong plugs!!

As Jim Royal would say "Merc expert my as5"

 

[roofless]

this gives some good info on bosch plugs ect http://www.scribd.com/doc/2677582/BOSCH-Spark-Plug-Guide-Official-Bujias-Bosch

 

[television]

Thanks Malcolm, I still think it's bad for a garage to fit the wrong plugs!!

As Jim Royal would say "Merc expert my as5"

Yes that is wrong and they should replace them with the correct ones, that is what you paid for