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Thread: Bosch spark plug supersession list and helpful hints

  1. #1
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,249

    Default Bosch spark plug supersession list and helpful hints

    http://www.bosch.co.nz/content/langu...449_Poster.pdf

    Helpful Hints

    Normal condition
    Insulator nose greyish-yellow to russet brown. Engine is in order. Heat range of plug correct. Mixture setting and ignition timing are
    correct, no misfiring, cold starting device functions correctly.
    No deposits from fuel additives containing lead or from alloying constituents in the engine oil. No overheating.

    Soot - carbon fouled
    Insulator nose, electrodes and spark-plug shell covered with velvet-like, dull black soot deposits.
    Cause: incorrect mixture setting (carburettor, fuel injection ): mixture too rich, air filter very dirty, automatic choke not in order or manual choke pulled too long, mainly short distance
    driving, spark plug too cold, heat range code number too low
    Effect: misfiring, poor cold-starting performance.
    Remedy: set mixture and cold-starting device correctly,
    check air filter.

    Oil-fouled
    Insulator nose electrodes and spark-plug shell covered with shiny soot or carbon residue. Cause: too much oil in combustion chamber. Oil level too high, badly worn piston rings, cylinders and valve guides. In two stroke gasoline engines, too much oil in mixture.
    Effect: misfiring, poor starting performance.
    Remedy: overhaul engine, correct fuel-oil mixture, new spark plugs.

    Lead deposits
    In places the insulator nose is glazed brownish yellow; this may also tend towards green.
    Cause: fuel additives which contain lead. The glaze appears in the case of heavy engine loading after lengthy part-load operation.
    Effect: under heavy loading deposits become electrically conductive and cause misfiring.
    Remedy: new spark plugs, cleaning is pointless

    Heavy lead deposits
    In places the insulator nose is thickly glazed brownish-yellow, this may also tend towards green.
    Cause: fuel additives which contain lead. The glaze appears in the case of heavy engine loading after lengthy part-load operation.
    Effect: under heavy loading, deposits become electrically conductive and cause misfiring.
    Remedy: new spark plugs, cleaning is pointless

    Formation of ash
    Heavy ash deposits from oil and fuel additives on the insulator nose, in the scavenging area and on the ground electrode. The structure of the ash is loose to cinder-like.
    Cause: alloying constituents, in particular from oil,can deposit this ash in the combustion chamber and on the spark-plug face.
    Effect: can lead to auto ignition with loss of power and engine damage.
    Remedy: repair engine. New spark plugs. Possibly use other oil.

    Partially melted centre electrode
    Centre electrode partially melted, blistered,spongy insulator tip.
    Cause: overheating due to auto-ignition, e.g. due to
    over-advanced ignition timing, combustion deposits in combustion chamber, defective valves, defective ignition distributor,
    inadequate fuel quality, heat range possibly too low.
    Effect: misfiring, loss of power (engine damage)
    Remedy: check engine, ignition and mixture formation.
    New spark plugs with correct heat range.

    Centre electrode melted away
    Centre electrode melted away, ground electrode also severely attacked.
    Cause: overheating due to auto-ignition, e.g. due to over-advanced ignition timing, combustion deposits in combustion chamber, defective
    valves, defective ignition distributor, inadequate fuel quality.
    Effect: misfiring, loss of power, possibly engine damage. Overheated centre electrode may result in insulator nose cracking.
    Remedy: check engine, ignition and mixture formation.New spark plugs.

    Partially melted electrodes
    Cauliflower-like appearance of the electrodes. Possibly deposition of foreign matter.
    Cause: overheating due to auto-ignition, e.g. due to over-advanced ignition timing, combustion deposits in combustion chamber, defective
    valves, defective ignition distributor,inadequate fuel quality.
    Effect: loss of power prior to complete failure (engine damage)
    Remedy: check engine, ignition and mixture formation.New spark plugs

    Heavy wear on centre electrode
    Cause: recommended interval between spark plug changes not complied with.
    Effect: misfiring, particularly when accelerating (ignition voltage no longer sufficient for large electrode gap) Poor starting performance
    Remedy: new spark plugs.

    Heavy wear on ground electrode.
    Cause: aggressive fuel and oil additives. Unfavourable influence of gas turbulence in the combustion chamber, possibly caused by deposits.
    Knocking. No overheating
    Effect: misfiring particularly when accelerating (ignition voltage no longer sufficient for large electrode gap). Poor starting performance.
    Remedy: new spark plugs.

    Insulator nose breakage
    Cause: mechanical damage due to being struck or dropped or due to pressure on the centre electrode when improperly handled. In
    borderline cases – particularly when the spark plug has been in use for too long – the insulator nose may be cracked by deposits
    between the centre electrode and the insulator nose and by corrosion of the centre electrode.
    Effect: misfiring. Spark jumps across at points which are not reliably reached by the mixture.
    Remedy: new spark plugs

  2. #2
    Join Date
    Dec 2004
    Location
    Sydney, Australia
    Posts
    4,374

    Default Nowhere near as good as my listing of BMW compatible NGK plugs...

    Nowhere near as good as my listing of BMW compatible NGK plugs...

    http://www.bimmernut.com/forum/showthread.php?t=42653

    LOL.

    But it is really good diagnostics info, esp. for the garage wall. Must print one nice and big!

    Thanks Erich!

    Join the Aussie
    540i LE yahoo forum

    08/88 535i e34 M30+miller MAF, 'stiens, tints & teeth!

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