73 F motor with low to no compression?

Discussion in '40- & 55-Series Tech' started by mooker82, Aug 10, 2005.

  1. mooker82

    mooker82

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    Looking at a 73 cruiser project trail rig. Owner says that the engine lost power and appears to have little to no compression. Mileage on the truck is around 90,000. Is there anything I can to do get the compression up short of a rebuild. Does anyone know any tricks? Engine restore? 90Wt gear oil in motor? How bad is it to replace the piston rings on this motor.
    thanks
    Steven
     
  2. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    Re-ringing the engine is not that big of a deal, but I would try and figure out why it has ' low compression'....



    Hell, the valves could be out of adjustment. :rolleyes:



    Good luck!


    -Steve
     
  3. mooker82

    mooker82

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    Guy stated he was driving and motor lost compression. He shut it off and has not messed with it. No compression #'s and he does not know how to do a check. No water/antifreeze in the oil so thats a good sign.
     
  4. fj40Matt

    fj40Matt

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    If he doesn't know how to do a compression check, how does he know it simply lost compression? What about carb problems, ignition, vacuum leak? If it is compression a burnt valve is also a likely possibility. A leakdown test can also identify the compression loss.

    Can't find a solution if you don't really know the problem.
     
  5. IDave

    IDave

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    I think you should be getting the truck at a very deep discount! :D
     
  6. HawkDriver

    HawkDriver

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    Well YOU could always just get a gauge and check yourself before you buy the thing. This can cause low compression too. Disregard the other info, talkin bout the blown out part between the two cyl.
    IMG_0001.JPG
     
  7. 65swb45

    65swb45 Elder Statesman Supporting Vendor

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    ARRGH! BRings back old memories.

    I bought a nice 76 fj40 from a guy with a similar story one time. Said he had changed the head gasket after his roommate overheated the truck. Said the engine was frozen and dumped the cruiser on me.

    I took him at his word and started making plans to strip the truck. Took deposits on the top, doors and windshield frame. THen I decided to hook up the battery and check all the switches before I stripped the electrical out. My buddy accidentally bumped the ignition and the engine turned over! :eek:

    What? FROZEN ENGINES DON'T TURN!

    I pulled the oil filler cap off and watched the rockers swinging WILDLY!. Pulled the valve cover, readjusted 12 OVERTIGHTENED rocker arms and started the seized engine up on this now topless, doorless, windshield-less cruiser. :eek:

    Won't make that mistake again.

    With any luck, this would be your problem.
     
  8. mooker82

    mooker82

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    I think its going to be a good deal for what I want to use the truck for. If I get up there to buy it and it does not appear fixable then I will just stop on my way back home to a fellow mudders house and pick up a used running 2F that they have for sale.

    More info from the seller:
    I was just cruising around my neighborhood when it lost power, (middle of an inter section). It had one large plum of white smoke come out from the back, loss of power happend at that point. The cruiser stalled and then started right back up, and drove me home, limping (with no power), but running. No knocking from what I could hear.
     
  9. azlar

    azlar

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    If you have access to a compressor, a leak down test will tell you a whole lot more about engine condition than a compression test.

    I was about to pull and rebuild an old Volvo b18 engine till I did a leakdown and found an overly tight intake valve

    -Laurence
    71 FJ-40
    65 356c
    misc other projects
     
  10. LandCruiserSteve

    LandCruiserSteve

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    Leakdown test

    I just did an extensive search, and all I could find were numerous threads suggesting that a leakdown test should be performed in addition to a conventional compression test.

    However, I couldn't find any step-by-step instructions for actually performing that test (i.e., equipment needed, procedure, determining the results, etc.). :confused:
     
  11. LandCruiserSteve

    LandCruiserSteve

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  12. CruisinTiger

    CruisinTiger

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    Yeah mooker get it for a cheap price bring it to the upstate and we'll help ya get it runnin. My guess like these guys said...carb issue, adjusting valve clearances, maybe bad fuel pump or cruddy fuel filter....I guess what I'm sayin is there is apossibility that the issue is a small easily fixable one. Good luck
     
  13. Gumby

    Gumby Supamod Staff Member s-Moderator

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    I generally do a leak down when a low compression number tells me there is a problem. I wouldn't go through the whole shebang unless I knew there was an issue.

    You need a leak down testing hose that adapts the spark plug thread to a air hose fitting.

    Remove the spark plug.

    bring the cylinder up to TDC for that cylinder. Both valves must be closed. You could also de-adjust the valves or pull the rocker shaft.

    put the vehicle in 4th gear and block the wheels well. The compressed air will try to push the piston down and turn the crank.

    open the throttle and block it open.

    Pull the dipstick or remove the fill cap. If you removed the valve cover to loosen the valves, you don't need to remove the fill cap. ;)

    Pull the radiator cap

    thread a leak down testing hose into the spark plug threads. On my Snap on compression tester, it has air hose fittings on the compression tester hoses, but you do need to remove the schreader valves from the hoses to use as leak down adapters.

    Add air.

    Check where the air leaks out.

    Carb = intake valve

    Exhaust pipe = exhaust valve

    dipstick or filler cap = rings or hole in the piston.

    radiator = blown head gasket or cracked head

    The amount of air leaking out is also an indicator of how bad it is. If you just have a slight pressure at the dipstick tube, you probably have little to worry about. If the air coming out the dipstick tube is the same velocity of the air you are putting in, you should say bad words and possibly weep a little.
     
  14. LandCruiserSteve

    LandCruiserSteve

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    Gumby -

    That's the first time I've seen a leak down test described in logical detail like that. Very informative and very helpful.

    Thank you VERY much!!!! :D :D
     
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