Announcement

Collapse
No announcement yet.

Zero compression on a new installed head

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Zero compression on a new installed head

    The Story:

    I had a couple of leaking valves in the 1st cylinder so i removed the head, hand machined them and reinstalled the head.
    I started the car and i checked compression, but the situation was a little bit worse.
    No problem.
    I removed the head again, taken it to the machinist where it was entirely renewed (valves, seats, guides) and polished.
    The leak test was done with a vaccum meter, it seemed everything was OK.
    Today i reinstalled the head, all the torques to spec, but when i started the engine i realized that it wasn't igniting at all, zero compression in all four cylinders.
    The starter motor drives the cranckshaft and the cams rotation, but there are no compression strokes.
    It runs freely like the head doesn't even exist :lostme:.

    I was thinking to a timing issue.
    Even if i had placed cyl #1 at TDC (by the sign on the pulley and the protrusion on the chain cover), and camshafts marks aligned with the slots on the bearing A1 and E1 (i had a picture to dont get mixed up).

    Well it seems i haven't got mixed up, but i messed it up.[peace]
    power is nothing without drift

  • #2
    hmmmm

    did you try putting the spark plugs back in?....lol














    http://garage.s14power.com/showgalle...08&ppuser=1534

    Comment


    • #3
      absolutely yeees.
      I also checked compression.
      zero.
      The needle of the gauge simply shakes a little but remains under 1 bar.
      power is nothing without drift

      Comment


      • #4
        Did you put a new head gasket in? :P
        sigpic

        Comment


        • #5
          Do a leakage test. Bring the cylinder to exactly TDC, pump air into the spark plug hole at about 80 PSI, then locate where the hissing sound is coming from.

          Are the valves adjusted properly?
          Last edited by jimmyC; 09-09-2007, 02:46 AM.

          Comment


          • #6
            How long did the engine sit with the head removed?
            was There a lot of carbon In the combustion chambers?



            How did you perform this compression test?

            crank the engine with wide open throttle?

            m

            Comment


            • #7
              Originally posted by Mmark View Post
              How long did the engine sit with the head removed?
              was There a lot of carbon In the combustion chambers?

              Well the engine was opened (after the first reinstall) on the 13th of august and stayed open till yesterday with the block protected by domopack plastic film for food and a towel.
              There was not a great deal of carbon.
              The head was cleaned and the pistons where light brown colored.
              The spark plugs were not oil soaked after the test.
              So i'm not inclined to think to a rings failure.



              How did you perform this compression test?

              With the same instrument i used on the first head reinstall (the one that went good )

              crank the engine with wide open throttle?

              Absolutely yes.

              m
              Originally posted by Nick-NY View Post
              Did you put a new head gasket in? :P
              Oh yeeeees :P

              Originally posted by jimmyC View Post
              Do a leakage test. Bring the cylinder to exactly TDC, pump air into the spark plug hole at about 80 PSI, then locate where the hissing sound is coming from.

              I can't do this 80psi test unfortunately.
              The head valve/seat sealing was checked directly on the head by sucking air off the intake and exhaust ducts.
              When the gauge hit the -0,5 bar value the machinist said "it's really ok".

              Are the valves adjusted properly?
              The valves were reinstalled from the machinist.
              He gave me a plug and play head.
              What's the procedure to check for adjustment?
              power is nothing without drift

              Comment


              • #8
                Did you make sure the shims where adjusted properly before cranking the engine?
                -Tony-
                1991 M3 10Km
                1989 M3
                BEGINS HERE


                Comment


                • #9
                  This can be telepathy i guess

                  The cleaning lady run onto my lifters with the vaccum cleaner.
                  So they got mixed up, but they where just three months old (the bottom of the engine was rebuild on may.
                  I measured them with a precision of 0.05mm and they were still of the same height (shims installed).
                  So i reinstalled them not in the same order they came out, but i tought that they were so new.
                  Does a <0.05mm wrong lift cause such a disastrous leak?
                  This is not a leak is just 0 bar...i really wish it was a leak :shit:


                  AND THANK YOU ALL INDEED (i'm in a state of depression you know :shit: )
                  :thank you

                  P.S. for jimmy: i'll try to find a compressor to perform the test you suggest
                  Last edited by france320isco; 09-09-2007, 05:50 AM.
                  power is nothing without drift

                  Comment


                  • #10
                    "10. Valve clearance specifications should be indicated on a sticker on the driver's side shock tower. This sticker recommends 0.28mm to 0.33 mm (0.0110" to 0.0130") cold for both intake and exhaust." (Gustave)
                    -Tony-
                    1991 M3 10Km
                    1989 M3
                    BEGINS HERE


                    Comment


                    • #11
                      Okay.
                      I'll recheck also the valve clearance.
                      And i'll try to find a compressor to blow
                      power is nothing without drift

                      Comment


                      • #12
                        Are the lifters installed in the cam carrier?! Could you have mixed up the timing marks on the cams (timing the intake using the exhaust mark, and the exhaust using the intake mark)? Bad compression gauge? Hole on the hose? If you put all the spark plugs back in, and turn the engine by hand, is there uniform resistance, or does it get harder to turn as you approach TDC, then easier past TDC?

                        Did you ever check the valve clearances? If you have zero clearance, the valves will never close so you won't have any compression. If they lapped the valves into the seat, they will sit higher that before. If you didn't check the clearances after the machine work, chances are they are all too tight.

                        HTH,

                        -Luis

                        Comment


                        • #13
                          Originally posted by marques View Post
                          Are the lifters installed in the cam carrier?! Could you have mixed up the timing marks on the cams (timing the intake using the exhaust mark, and the exhaust using the intake mark)? Bad compression gauge? Hole on the hose? If you put all the spark plugs back in, and turn the engine by hand, is there uniform resistance, or does it get harder to turn as you approach TDC, then easier past TDC?

                          Did you ever check the valve clearances? If you have zero clearance, the valves will never close so you won't have any compression. If they lapped the valves into the seat, they will sit higher that before. If you didn't check the clearances after the machine work, chances are they are all too tight.

                          HTH,

                          -Luis
                          Thanks.
                          Yes, the lifters are installed in the cam carrier.
                          I aligned cams like http://www.s14.net/forums/showthread...engine+rebuilt
                          the same position was also showed in the manual that i own, with the O|T mark on the pulley aligned with the chain cover protrusion.

                          Is it possible that this alignemt wont work in some condition?

                          Like i said, i've had installed the head also before the refurbishment, to check compression and the engine compression strokes were OK, with the same cams/crank alignment.
                          I could eaisly start the engine.
                          It was the lack of compression in the 1st cylinder that brought me to take the head to the machinist.

                          The compression gauge works OK, i checked it in an hardware store .
                          Don't know the hose.

                          For the last question: it is a yes, the rotation is harder and then easier during the turning when spark plug installed.
                          But there are no compression strokes when rotating by starter motor.
                          When i crank the engine by the starter motor with the spark plugs removed, i can also see mixture spurts from the plugs holes.
                          (i only did it twice, to dont wash the oil).
                          But this strokes are not sufficient to raise the gauge needle that only oscillates from 0 - 1 bar.

                          I dont know if the machinist lapped the valves into the seats (they are both new), but i can tell that looking at the combustion chamber with valves installed, i can clearly see that they are higher (comparing with the old seats/valves condition) with respect to the seats plane.
                          This would mean that the valves (and lifters) sit lower with respect to the cams then in the before machining condition.



                          So what to do since now with the help of you all:

                          1) 80 PSI test
                          2) valve clearance check
                          3) timing check (??)
                          4) check the hose of the compression tool

                          Thanks again
                          Last edited by france320isco; 09-09-2007, 08:20 AM.
                          power is nothing without drift

                          Comment


                          • #14
                            Is there any chance the guides were improperly installed, and are causing the valves to say open? I'm not even sure this is a possibility on the S14, but on some engines, if the guide is pushed too far into the head, the valve flare (where the stem transitions to the valve disk) may actually touch the bottom of the guide.

                            The S14 guides have a circlip that's supposed to ensure the guides are at the correct depth in the head. Is there any chance the guides are pushed too far down. (The throttle bodies are off my engine at the moment and I just looked down the intake ports with a flashlight -- I don't there's a chance that the guide is interfering with the valve operation -- there's plenty of room betweent the bottom of the guide and the valve body....)

                            Have you done a "wet" compression test after squirting a bit of oil into each cylinder? I'm wondering if the rings might not be sealing if the engine sat very long.
                            The day ain't over yet....

                            Comment


                            • #15
                              Well i'll check also the possible interfering of valves/guides but i doubt it cause a leak test was performed on the head.

                              My block sat since the 13th of august till yesterday, protected by a transparent plastic film for food and a towel.

                              If there was a total rings failure that gives 0bar compression i thik i should have seen the bottom of the cylinders/spark plugs full of oil.
                              (i could see this during a massive rings crack in the first cylinder on another engine. With the spark plug oil soaked i still could read 4-5 bar of compression).

                              The timing thing is what get on my nerves.
                              In point of fact on the first head re-install, i timed the engine aligning cams/crankshaft as i told before, without have touched the cranck position at TDC (has i found it when the head was removed).

                              On yesterday reinstall i gave a couple of turns to the crankshaft to lubricate cylinders a little, then i reached again the 1st cylinder TDC and i've reinstalled the head.

                              On the cams there are a total of 4 marks, which means that i have 4 possible relative alignment with respect to the notch on the front caps and the TDC O|T mark.
                              In other words, once i'm at TDC in the 1st cylinder, i have four possible cams alignments.

                              Are they all equivalent?
                              power is nothing without drift

                              Comment

                              Working...
                              X