This is a 16 valve DOHC

Between the In and Out cams I notice slack in the chain. Slack is about 3/4 inch over a 1 foot span. I turn the crank a little and the slack is gone. Turn some more and the slack is back.... This aint normal, is it?

Car has near zero compression. This happened suddenly after moving the car across the driveway.

Is a 2002 saturn 2.2 liter.
sever dirt roads, gunk under valve cover 1/2 inch deep.

thanks

The cam lobes make "hills" that push the sprocket "downhill", so under slow rotation, the cam may counter-rotate, giving the slack where you note it. That is not a definite indication of jumping time, or having a bent valve. Make sure you are rotating the engine the right direction. Rotating the wrong way can put excess slack on the untensioned side and the belt can jump, and you may well bend a valve. I'm not up on that engine, but it may have a hydraulic belt/chain tensioner that is not under pressure unless the engine has oil pressure, and/or the tensioner spring may be dying. Hand rotate the engine slowly and gently in the correct direction (so the cam sprocket pulls on the untensioned side of the chain/belt) through two complete revolutions of the crank (one revolution of the cam sprockets) to see if there's any valve interference. A bent valve may not show up in this test. Then rent a radiator tester and see if the head gasket is leaking. Then take the head off and see what the problem really is...

The Gates website shows all the engines are interference engines, but that's only for the rubber band engines. If you have a chain, it's not on that list.

Thanks eddy. I have found some info on checking the chain marks and that is where I will start. If it is gasket or valve problems the chain/cover will have come off anyway. I think the tensioner is hydrolic, but info is sketchy.

The valves seen to be closing fairly well when positioned with lobes up and compressed air applied.

The zero compression is a puzzle. There is a TSB that says
sticking valves caused by low quality gasoline will cause this. Says use top end cleaner... so I pour some seafoam/gas/oil mix in the hole and shoot air in with valves near closed. Still no compression when cranking.

I will start tearing in to the chain covers.

oh, a radiator pressure testor. I have one but the cap adaptor does not really fit. It will seal if held in place, though. I will try to figure someting out

This radiator is the type with the cap on a bottle off to the side.

nothing worse than people who post a question then never reply with a fix - I aint one a thum

So, this chain was in fact jumped. The first clue was the slack noted. I put the chain back according to best info I could find and it started.

it seems that this engine had a recall for chain oiler being too small and wearing out crank sprockets or something like that. At least the parts were updated and it seems this one had the updated tensioners (black, not some other color.) I think the crank sprocket is worn and chain is weak.

Thanks eddy, when I get this fixed I can cruise it down to the JY and search for a GEN-1 ashtray.

That engine is known for problems. The SOHC has been a good engine though. I would look into the chain tensioner as well, sounds like it lets the tension back off a bit much. I would expect the lower sprocket might have a bit of wear to it too.