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no Compression on rebuilt EJ20
Posted: Sun Jan 06, 2008 3:31 am
by cuillin
Car is a 1990 GT wagon with RS engine/box EJ20 Turbo
Had Cylinder heads rebuilt, surfaced, valves seated and new lifters fitted.
Assembled engine with new cambelt and tensioner, all timing marks appeared to be spot on.
Turned over engine by hand,plenty of compression all seemed well
Engine started fine, after a few seconds what sounded like a mechaical knock appeared.
Engine was shut down and after a compression test it read 0psi
in all cylinders.
Heads removed for fear of bent valves however there were no marks on any pistons and all the valves looked normal.
Pics avalible if required.
Any ideas ? I'm stumped as it all looks fine
Posted: Sun Jan 06, 2008 9:38 pm
by Arctic Assassian
bad compression gauge?
Posted: Sun Jan 06, 2008 10:13 pm
by evolutionmovement
Did you make sure the cams were still oriented correctly after the compression loss? Perhaps the belt tensioner died.
Posted: Mon Jan 07, 2008 6:14 am
by cuillin
All the cam marks wer orientated correctly as far as i know with the valves looking fine and there being no marks on the pistons im starting to think that the compression tester is stuffed .
Heads have gone to engine shop to be checked just incase so should find out within the next few days
Posted: Wed Jan 09, 2008 4:45 am
by cuillin
I got the heads back and they checked out fine so im guessing the compression tester i borrowed was broken, that was a costly mistake.
Posted: Wed Jan 09, 2008 5:07 am
by Arctic Assassian
I already told you... There is no reason you would ever have zero compression. ever. Unless the motor you were testing was incomplete...without rings, or valves.
Posted: Wed Jan 09, 2008 7:14 am
by 555BCTurbo
Arctic Assassian wrote:I already told you... There is no reason you would ever have zero compression. ever. Unless the motor you were testing was incomplete...without rings, or valves.
Incorrect.
If your lifters were holding the valves open too far, you would not have any compression.
Don't ask me how I know
Posted: Wed Jan 09, 2008 7:19 pm
by Arctic Assassian
That would be a fault of timing, or bad lifter adj.?
Posted: Thu Jan 10, 2008 2:05 am
by tmarcel
The way I generally do a comp test is to remove all plugs. Then start at one of the cyliders and make the way around. It takes very LITTLE effort for the motor to turn over like this. Almost sounds like a sewing machine as the starter cranks the motor. Does your motor sound like this? Spin without any effort?
If this had happened to me, I would first look to the cam timing. Then look at everything else.
As far as gauge readings, the cheap ones are terrible in terms of accuracy, but they should work to a degree, i.e high or low readings. If the gauge wasn't working at all, then wow I've never seen that.