Healthy motor with no compression?

norcals95 · Post by **norcals95** » 19 Jan 2012, 22:39

Not possible you say. Well after pulling my hair out on my 850 turbo I wanted to document my findings in case someone runs into the same issue down the road.

I forgot to plug my coil back in after doing a compression check (180 all 5 btw). Yes i did disable the fuel system for the compression check. Cranked engine for about 45 seconds before realizing my fault. Plugged it in and cranked. I got a pop and the sound no Volvo owner wants to hear...the starter doing no work because of no compression.

I compression checked it again. Keep in mind id just gotten 180 all the way across. I now had nothing. Timing belt was my first suspicion. Checked the marks and they were fine.

So, I was utterly stumped. Come to find out from a Volvo tech it's not unheard of that under extended crank without spark that the cylinder gets oil washed out with fuel and gives you the no compression issues I had. Dropped some oil in the cylinder and cranked for a good while. Compression is back to 180 and good to go. Just hoping to save someone the many hours it took for me to figure out. 1995 Volvo 850 turbo with CPU verified 134k miles.

If your as skeptical as I was about this it is in fact my first hand experience and I would have laughed if somebody had told me this that wasn't a Volvo tech. But it is possible to have a healthy engine with no compression. Lol

Post by **precopster** » 19 Jan 2012, 22:56

Not uncommon on this forum and documented as Lawnmower Syndrome.

This can happen on very short starts, just by moving the car a couple of feet to "get the lawnmower out" and stopping the engine before it has run for more than 15 secs. The oil washes down the cylinder before having enough splashed up into the cylinder walls and presto, you have no compression!!

If my 960 hadn't done this to me afew times now I wouldn't have believed it. VERY frustrating!!

norcals95 · Post by **norcals95** » 19 Jan 2012, 23:27

Oh ok. Wish I was able to find it on the forum earlier but still unbelievable to me.

Post by **tjts1** » 20 Jan 2012, 04:26

Lawnmower syndrome has more to do with the hydraulic lifters bleeding down after a short, cold engine run.

Post by **precopster** » 20 Jan 2012, 05:47

tjts1 wrote:Lawnmower syndrome has more to do with the hydraulic lifters bleeding down after a short, cold engine run.

In my experience (twice now) a squirt of oil in the cylinders has restored the compression. The starter was spinning furiously with almost no friction and the exhaust was only letting out a whimper of gases.

This wouldn't be the case with lifters lacking oil. The valves would stay closed and you would get vacuum then compression, vacuum then compression and you would hear strange weasing noises as inlet air is forced past the valve seats and rings. Pretty much like taking the rocker gear off a OHC engine and turning it over with the starter.
You would have to remove the cam cover to fix that on a Volvo whiteblock surely.

norcals95 · Post by **norcals95** » 20 Jan 2012, 07:03

^ exactly! I had the same wheezing from the intake area of the engine. I wish I had posted up a question earlier but I figured everyone would jump to the conclusion of bad timing, which obviously isn't the case. This is something that is obviously not uncommon with these 850's the more I ask around with Volvo owners. Hope I can save someone the headache I dealt with as I was about 20 min away from pulling the head to have it rebuilt until I had my doubts because of the perfect timing.

Post by **jimmy57** » 20 Jan 2012, 10:01

actually LMS is when the tappets overextend when the valves have deposits on stems and they get dampened on closing. The sluggishness to follow tappet allows tappet to fill with oil when it gets back on base lobe of cam and the oil fill hole now is aligned with oil port on tappet. The tappet will hold valve open .1-.3 mm and that is enough to lose compression. The fuel fog exiting the exhaust gets on stems and dissolves the deposit and makes it a goo that binds valve motion in guides.
You can get reduced compression from fuel wetted rings but that will not reduce compression to nearly zero like an off the seat exhaust valve will.

Post by **precopster** » 20 Jan 2012, 14:42

So when this happens, jimmy what do you need to do to get the darned thing started? Oil in the cylinder, then would do nothing.

With my 960 I have worn bores and high oil consumption so I'm not so sure it's the same thing.

FREEBUSINESSES · Post by **FREEBUSINESSES** » 27 Sep 2020, 09:45

Anyone know what else can cause zero compression on all 5 cylinders on 06 2.5T? Rebuilt head, all new valves lapped in valve seals, timing triple checked, still no compression.

FREEBUSINESSES · Post by **FREEBUSINESSES** » 03 Nov 2020, 22:22

Amazing, no input in two months. I am stumped, I squirted oil in each cylinder and compression came up about 10 lbs now at 15 lbs in cylinder 1 and 5 and still zero in all the rest, barely a puff with rags stuck in spark plug holes. My question is how can one cylinder bleed over to another, even if ever so little??? I got air spark plug connector and it appears cylinders do not hold air, none even if I crank engine by hand which should present a closed intake and exhaust at some point, so how is this possible??? Could rings be that bad, I know head is solid as all new valves and seals were installed and no interference when hand cranked and checked timing a dozen times. Someone suggested crank pulley can strip and throw off timing by 30 degrees without damaging valves, is this possible??? I hate to pull it off, so is there another way to determine this possibility???

Thanks, Hope someone is out there reading this forum.