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NO COMPRESSION!!!

Discussion in 'XJ Technical Chat' started by BOUNTY, Oct 23, 2014.

  1. BOUNTY

    BOUNTY New Member

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    Hello fellow riders. I have a couple of questions i need help with about my bike. I have a 1981 xj550 seca and it has sat from last summer inside. I drove it home and parked it. Now i crank it over and no start. I have spark and fuel, but i only have 25-30 psi compression on all cylinders. Oil is full. No external leaks from head gasket area, no external oil leaks. Pulled top cover and checked timing chain and cams, timing is dead on! Tore down engine and inspected block and head.Valves are seated and look ok, no cracks and cylinder head is straight (checked with straightedge and feeler guage.Pistons look ok and checked all rings.Now, I need to know the maximum wear on ring ends in cylinder and maximum wear limit on cylinder walls. What else could it be? Before i tore it down I added oil to cylinders and retested compression and got 90 psi on all. But after 2 days i would get 20-30 psi again. Any help would be appreciated!
     
    BOUNTY, Oct 23, 2014
    #1
  2. rocs82650

    rocs82650 Well-Known Member

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    Idk what the end gap piston ring gap spec for your model.
    When you're doing the compression test:

    1. Is the battery fully charged?
    2. Are you removing all the plugs?
    3. Is the tci disconnected?
    4. Did you remove the air filter?
    5. Is the throttle being held WO while the start button is being pushed?
    6. What's the condition of the compression testing equipment?

    Gary H.
     
    rocs82650, Oct 24, 2014
    #2
  3. tabaka45

    tabaka45 Well-Known Member

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    I would check the compression gauge. If it was running when you parked it it had to have more than 25-30 psi compression.
     
    tabaka45, Oct 24, 2014
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  4. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    My bet is on bad gauges.

    1. how did you check for spark?

    2. how did you check for fuel?

    dave
     
    hogfiddles, Oct 27, 2014
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  5. BOUNTY

    BOUNTY New Member

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    YEP BAD GUAGES!!!! WELL NOW I NEED A COMPLETE GASKET SET!
     
    BOUNTY, Oct 29, 2014
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  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    XJ4Ever. PM Chacal or click the dancing logo/link at upper right.

    Lesson learned: always get a "second opinion" when compression test results are unexpected. Borrow a different gauge if you don't happen to own two of them.

    Note upon reassembly: the galleries surrounding the outer two head bolts on the RH side are the oil feeds to the head. Those outer two cap nuts get copper/brass sealing washers, not the same washers as on the rest of the head.
     
    bigfitz52, Oct 29, 2014
    #6
    FtUp likes this.

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