stuck decompression lever

[Wayne Grenier]

I need some ideas-I had 2 dead batteries due to a bad alternator on my MD11 Volvo-so I flipped up the 2 decompresiion levers and now the one for the rear cylinder won't go back down-what do I do? should I take the rocker arm cover off? The motor did not start so I sailed back to the mooring- once I replace the alternator should I start the motor and see if I can back the lever back down or perhpas turn the motor over slightly to see if the lever frees up? has this happened to anyone before? thanks-

[John Vigor]

Wayne, I've never come across this problem before and I don't think I can be much help, but I wouldn't try to start the engine with compression on just one cylinder.

I've often seen warnings that you shouldn't stop a racing engine by using the decompression lever because it can cause damage.

If I were you I'd try to turn the engine over slightly by hand, or with a brief burst of the starter with the engine cut-off operated so that it doesn't fire up.

The compression lever is spring-loaded to shut itself off, but may just be sticky through lack of use. Try wiggling it when the engine and the cams are in a different position.

If that doesn't work, you're going to have to take a peek inside to see what's happening, and call in outside help if necessary.

Good luck,

John V.

[Oswego John]

I go along with what John V states. Like John, I've never seen a compression release lever hang up, either. Try the little, simple, easy things first. It sounds like something is mechanically stuck.

Almost everyone has his own favorite for freeing something when it's hung up. About in the last half of the 1940s, sometime around the end of the war, someone introduced me to Marvel Mystery Oil (MMO). Since then, until this very day, I have considered MMO as my favorite magical elixir when working on stubborn mechnical problems.

MMO is great for freeing up sticky valves and frozen piston rings. If it is easy enough to get at, you might consider pulling the valve cover and see what's going on inside the upper engine area. You may see if there is carbon or hardened sludge buildup. Maybe there is return spring malfunction.

Whatever the problem, a few spritzes of MMO should clean the upper engine area.

If things prove that it is too tight an area to work in to pull the cover, maybe you can remove the glo plug and shoot the MMO into the area of the compression release.

Good luck,
O J

[Wayne Grenier]

actually the engine starts and runs fine and is obviously running on both cylinders-it sounds exactly the same as it did before-I spoke to a mechanic who said it would be vibrating and shaking if the exhaust valve was not closing- the decompression lever is a lever that depresses the exhaust valve rocker arm a tiny bit to stop it from closing all the way-if somehow it would not release you would hear the lever and the rocker arm hitting-also-it only works in the straight up or 90 degree position-and I can flip it to the opposite side to where it originally was so I think I am ok-as an aside I asked the yard mechanic if he thought it was a good idea to remove the rocker arm covers and adjust the valves as well as see what the deal was with the decompression lever as the valves have not been adjusted in 20 years since the motor was rebuilt and he told me "if its running fine-leave it alone"-
so-I'll take the rocker arm cover off either when I pull the boat or when it gets cooler outside-or I'll keep trying to close it and maybe some time I'll get lucky-
thanks-