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Testing Results, Help/Confirmation needed Please

Discussion in 'XJ Technical Chat' started by LincsTriker, Aug 28, 2007.

  1. LincsTriker

    LincsTriker Member

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    Location:
    Lincoln, UK
    Hi Guys

    Engine was running badly, weak spark, low compression so....

    Over the past 2 weeks I have done quite a bit of work on my engine, the work carried out was full carb clean, lapped the valves, fitted new valve seals, new shims where needed to give a correct gap and new spark plugs.

    Compression test:
    cylinder 1 - 100 Dry / 125 - Wet
    cylinder 2 - 100 Dry / 120 - Wet
    cylinder 3 - 88 Dry / 110 - Wet
    cylinder 1 - 100 Dry / 125 - Wet

    Electrical Test:
    12.8 volts at battery
    With engine running at 2000 rpm:
    14.8 volts at battery
    12.8 - 13.7 volts at low tension end of coils.
    Resistance check across coils:
    Coil 1 & 4: 4.9 Ohms
    Coil 2 & 3: 5.1 Ohms

    All plugs "sooted" up (no oil), engine idles fine, and revs ok when in Neutral. When put under load, ie driving, splutters through 3000 rpm then goes ok and will easily get to 75 - 80 mph with 2 up. Engine then runs ok for a short while at low revs until the plugs soot up again. Engine is running hotter than back in July when we went to Belgium (840 mile round trip) when it ran great.

    My diagnosis:

    New coils needed. Based on the voltage at the battery and coils there is no need to touch the Alternator brushes.

    As the cylinder head has been rebuilt last week with new seals etc and everything is within the correct tolerances, I suspect I need new piston rings across all 4 cylinders.

    Can I confirm that I am approaching this in the right direction or am I way off? Any help would be appreciated.

    Cheers
    Lea
     
  2. Robert

    Robert Active Member

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    Location:
    Ventura CA
    I'll agree your coils leave much to be desired. Kick them to the kerb. I would still check your alternator brushes dispite your good numbers. Could be they are at the end of their lifespan all the same and it is easy to look into them.
    New rings would not be a bad idea at all, #3 is done.
    Good luck, may the force be with you.
     

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