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Low Compression on all 4 Cylinders

Discussion in 'Engine Building' started by polish, Aug 28, 2007.

  1. polish

    polish New Member

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    So I have been working out all the bugs from my motor swap. I got rid of all the check engine codes. The motor has spark and fuel (check at injectors). The damn thing still won't run.
    My buddy came over yesterday with a compression tester and all 4 cylinders read 27psi. At first I was super pissed because this motor was suppose to be a good motor. Then I began thinking what would cause this. Usually when a motor is bad you get knocking, clanking, noise from it. The motor is as smooth as can be when cranking. Also when a motor is bad it is usually 1 cylinder that has extremely low compression, right????
    What do you guys think??

    Is the timing off slightly where a valve is opened just enough to leak out the compression and not hit the pison????

    Any advice or help would be great.

    Leon
     
  2. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    Your engine probably has bent valves. If the timing belt snapped on it before there is a good chance. You wont really hear any funny noises when you turn it over but the valve could be bent resulting in the super low compression. Its pretty likely.
     
  3. polish

    polish New Member

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    Ya i could see how that could happen, but why would someone throw a new timing belt on it just to sell it to me.
     
  4. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    I dont know why people rip each other off but it happens all the time. The engine would obviously be worth alot less with bent valves. But if this is the case with your engine and you are pretty mechanically inclined it wont be too big of a deal as long as the bottom end didnt suffer any damage. If the valves are bent I would take the head to a machine shop have them replace the bent valves and perform a valve job while their at it.
     
  5. polish

    polish New Member

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    well I actually have my old head from my old b16 that is in perfect condition!!!!! It was the bottom end that went on the old motor.
    I could slap that one on there.

    Ill probally check the timing before I do all that work.
     
  6. polish

    polish New Member

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    You need a compression tester from Autozone or Checker. After you have one you pull out the spark plugs, thread the compression tester in one of the spark plug holes and then crank the motor.

    Thats is it man!!!!
     
  7. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    Yeah blanco is right, if you didnt have the throttle open all the way you will need to try it over again.
     
  8. polish

    polish New Member

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    Sorry, man. I feel like an ass. I thought you were asking how to check it. :)

    My buddy and I took all the spark plugs out, threaded the compression tester and then jump the negative battery post to the starter and cranked it for about 5 seconds on each cylinder. We however did NOT open the throttle at all.

    Is this the wrong way????
     
  9. MXDesa

    MXDesa Senior Member

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    Opening the throttle will help, but is not needed. It will only net you a few pounds difference. I would also be inclined to say that your valves sound like they are bent or off timing.
     
  10. dtob

    dtob New Member

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    Ya check your timing. If its not off I'd have to agree with the bent valves.
     
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