MatthewLaSon Jul 28, 2010:

Hi It does seem that there is no compression. Could it be that the valves are getting hit by the piston, leading to no compression because of the revving up (enging turning too fast)? So, the engine is compressing in vain????

appuie = compressing?
dans le vide = in vain

See this link:

http://www.thetechzone.com/forums/showthread.php?threadid=46...

If the valves get hit by the piston you will lose compresssion and have major drivability problems. You can do a compression check, but if its still running fine then chances are that you did no damage.

Amanda Grey (asker) Jul 27, 2010:

Sorry I should have mentioned We are talking about the 18-speed engine for a 40T truck... The optimal engine performance is between 1000 and 1500 rpm.
Loses compression (hence power) is probably the best option here.

MatthewLaSon Jul 26, 2010:

dans le vide = sans conséquence, imho I know if you say "le bouton de quelque chose ne fontionne pas", j'appuie dans le vide". That means that the button isn't working and you're just pressing it in vain.

Terry Richards Jul 26, 2010:

I'm afraid I disagree What's the mechanism for this loss of compression? It can only happen if the piston group fails or the valves cease to close. Any loss of compression due to piston group failure would be permanent which doesn't seem to be the case here. The only thing temporary that could happen would be valve float and I'm having a hard time buying valve float at 1500 rpm.

Amanda, what type of engine is this?

MatthewLaSon Jul 26, 2010:

appuie dans le vide I believe that it means that the engine is turning but there is no compression.

appuie dans le vide = pressing into nothingness/emptiness

... and new chain. after install, engine turns but no compression, checked timing it was fine, marks line up. just no compression, ...
http://www.automotiveforums.com/t298974.html

So, I do sort of agree with Transitwrite, but I don't have the possibility of agreeing with her as I'm not a ProZ member. However, I would say "no compression", rather than "lack compression", as the latter implies there is possibly some compression but not enough.

Terry Richards Jul 26, 2010:

I'm not allowed to answer... ...but I think "runs out of steam" might be appropriate here.