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Spark Plug question 1800cc engine

Discussion in 'Fuel System & Electrics' started by Burnstar, Sep 6, 2015.

  1. Burnstar

    Burnstar Member

    Messages:
    98
    Location:
    Artarmon
    I'm a bit confused on which plugs I should be running...

    My bus is a 1974 1800c twin solex with electronic ignition.

    I pulled out the spark plugs as it was running rough, they plug looked ok except for No.1 which was black (dry), the existing plugs were NGK BR7ES, I went to a couple of places but they didn't have these in stock so they gave me Bosch WR7CC instead. Put those is but it didn't solve my issues so I took the bus to the mechanic who put it down to a loose earth wire from the battery.

    However the kombi is now backfiring when cold and gets mostly good after 15 mins of running, I pulled out the No.1 plug again and it black (dry), the same as the previous plug.

    I just looked up Ratwell and it says I should be running WR5CC as an equivalent for the NGKs.

    I will be taking it back to the mechanic to have a look but I just want an understanding of which plugs I should actually be using?

    The Bus is based in Sydney.
     
  2. cbus

    cbus Well-Known Member

    Messages:
    13,444
    Location:
    sunshine coast
    safest bet is NGK B6ES or BP6ES ,BP6EY not much between them
    if the bosch are not german they may be faulty

    the R is resistor and shouldn't matter but you don't need it .
    You should use wire core leads if running the bakerlite resistance connectors
    the 7 in NGK is too cold for normal use and are taking too long to warm up.

    check all plugs again for colour if it will run smoothly enough to give it a full warm up and hwy run.
    the fluffy black says its too rich or the plug isn't firing. if only one cyl most likely lead or plug rather than mixture
    are they all the same colour now?

    sounds like you have only no.1 cyl faulty ?
    if so and warmer plug doesn't fix then its likely that your lead is faulty. should hear the difference when you replace it

    otherwise swap the cap.
     
    Burnstar likes this.
  3. Burnstar

    Burnstar Member

    Messages:
    98
    Location:
    Artarmon
    Swapped the plugs for the BP6ES and it is not backfiring anymore, however it does feel like it is only running on 3 cylinders, swapped for a new lead and no difference. It's booked in to the mechanic now so he can figure it out what the problem is.

    The No.1 plug was black again after having only been cleaned yesterday, the other 3 plugs were nice and healthy.
     
  4. cbus

    cbus Well-Known Member

    Messages:
    13,444
    Location:
    sunshine coast
    remove one lead at a time from each spark plug while its running. pull on the connector, NOT the lead.

    note how much revs drop for each cylinder
    my guess will be that minor or nil difference with no, 1 off and almost stalls with each of the others .

    the other check is to pull no1 lead. insert a spare plug. start engine. earth metal body [near hex] on motor[fan shroud will do].
    see if you have a spark.
    if so its probably weak.

    alternately. as you pull ech led from the plug in each cylinder you should hear a strong spark as you hold it about 10mm from the top of the plug. Or it may short to the engine with a sharp crack and visible blue/yellow spark..
    try another lead or test it by using on another cylinder [in correct firing order] to ensure it works] a multimeter test for continuity is good if you have one.

    if spark plug test on no 1 shows a strong spark then probably your electrical side is ok and prob is elsewhere.

    check valve settings on no 1 as well
     
  5. Burnstar

    Burnstar Member

    Messages:
    98
    Location:
    Artarmon
    I'll give that a try.
     
  6. Burnstar

    Burnstar Member

    Messages:
    98
    Location:
    Artarmon
    Got the Kombi back from the mechanic, apparently the number 3 spark plug lead was loose (I thought I'd checked all of them!!) they also changed the gaskets on the muffler, removed some loose bits from the muffler and welded some holes near the heat exchanger and it is now a lot quieter.

    They also adjusted the fuel mixture in the carby (they will need reconditioning within the next year due to some worn seals allowing air to leak in)

    The kombi is now running well and I'm looking forward to camping this weekend !
     

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