0 compression while cranking / Leak Down Holds???

[99SpyderGS-T]

After a mishap a couple of months ago with my cylinder head I am in the process of putting a 1G head on my 2G. Before I got too far on reassembly I thought I would check compression. 2,3, and 4 were 155, 160, 155. #1 is 0. I thought maybe I had a serious leak or something so I cranked #1, by hand, to TDC and gave it a 100psi for a leak down. 30 minutes later it is still holding the exact same pressure. The only thing that I can guess is valve timing. Tomorrow I will get someone to help detect any air loss during cranking.

Other info: Before putting the head on I rotated the cams several times making sure the valves were functioning properly. I did the ghetto valve test of placing each cylinder with both sets of valves closed and filled it with paint thinner. Each cylinder held quite well. After assembling the motor I turned it over many times by hand without notice of any problems. At this point I have not tried starting the car yet only turned it over with the injectors still unhooked.

Can my cam timing be off and still have the other three cylinders show good compression? Any insight will be appreciated. Thanks!!!

 

[zxdude]

my car did that when my lifters locked up.... cost me an extra $300 when i tried to start it and bent 3 valves....

 

[wrecko]

is it possible u have the 2 cams reversed? meaning exhaust cam is in the intake side? though if thats the case i think 2 cylinders wouldnt regster compression, this is interesting, please let me know how it turns out..

PS try a leak down with that piston in its lowest position possible with all 4 valves closed. maybe the cylinder wall is messed up on 3/4 of the wall and only allowing it to seal at tdc on that piston, hence why you get a good leak down at tdc

 

[ryanman]

You sure your gauge didn't #### up or the release valve didn't stick open?

 

[99SpyderGS-T]

I should have also mentioned that before pulling the old head that I had 130+ compression on #1 even with the questionable head gasket.

At this point I don't think that the gauge is at fault as I tried #1 four times, removing the gauge from the head and rethreading each time. The other three cylinders hit first time.

I will try the leakdown with the piston at BDC and see what happens.

 

[99SpyderGS-T]

OK, figured out that I was not doing the leakdown test properly. I have a ton of air coming out of the exhaust side of the head. Sing the cams are not in a position to be opening the valve I am going to guess that one of them is stuck open. I am pulling the head again aren't I?

 

[zxdude]

with the valve cover off you could try prying up on the stuck valve/s, but chances are you bent the stuck valve. = new valve and the seats need to be re-done.

 

[99SpyderGS-T]

I am hoping that I have not bent any valves at this point as I have not tried starting the car. I turned the engine over several times by hand after re-installing the timing belt and saw no resistance. I did turn the motor over for the compression test but heard nothing out of the ordinary. In fact I can still turn the engine over by hand without too much effort. With this in mind I just popped the rockers off of the exhaust side of #1. With a leakdown I no longer hear air from the exhaust port. I instead hear (and slightly feel) air from the plug hole of #s 3 and 4. Does that make any sense? As mentioned in my original post above I had good compression in 2, 3, and 4. I think that I am going to pull all of the lifters and give them a good cleaning and will check each cylinder when there is no pressure on the valves.

 

[99SpyderGS-T]

Just to update for anyone that may run across similar symptoms here is my progress: It looks like a stuck exhaust lifter was my problem, I have now removed all lifters and have them soaking in acetone. With the exhaust rockers off of cyl 1 I compression checked all cylinders while number one is lower than the others it is still at 155 wet. I will reassemble after cleaning all of the lifters and then check compression again.

 

[99SpyderGS-T]

After cleaning and oiling all of the lifters tonight I found myself right back at the exhaust valve leak. Strangely enough I have narrowed it down to one of the rockers apparently not fitting properly. I do not know the history of this head as I was told it was removed from a running vehicle. I put in a lifter from another head I have laying around and hit 160#. Will I be OK running with this mismatch rocker? Do any of you still suspect the lifter? It seems to function properly and I swapped it with another one and did not see any change in compression.