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  What's a 'Check Valve'?

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Author Topic:   What's a 'Check Valve'?
RichAA posted 07-24-2002 03:39 PM ET (US)   Profile for RichAA   Send Email to RichAA  
My Merc 40 (which might have 30 hours on it) wouldn't start this spring so I took it in to the dealer and had them fix it. They said it needed a 'check valve' and that I must have had a backfire or something.

I've never heard of it. Anyone?

1983 Sport 15, 1996 Merc 40

DaveH posted 07-24-2002 03:54 PM ET (US)     Profile for DaveH  Send Email to DaveH     
A check valve is an oriface which only allows fluid flow in one direction. A simple design uses a spring-loaded ball as a check device which requires slight pressure to unseat the ball. For your fuel system, I havn't the foggiest what type they would use. Hope the definition at least helps you.
Bigshot posted 07-24-2002 04:10 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Usually in a fuel tank to keep the gas from flowing back in. 2 strokes do not really backfire, if they do it is usually out the carb and there are no check valves in there. The only ones are on tilt pumps, gas and oil tanks that I know of.
jimh posted 07-24-2002 06:25 PM ET (US)     Profile for jimh  Send Email to jimh     
"Check" is a great word. There are many meanings. In this sense it means to restrict.

In hockey, a player slows down an opponent by giving him a check.

On the Great Lakes, freighters are required to "check down" or to "run under check" (slow the speed of their main engine) when passing certain places.

A check valve restricts the flow through of material through the valve. If it only restricts in one direction then it's a "one-way check" valve. That is usually the meaning intended when someone uses the phrase "check valve".

Are there more meainings? Let me check...

RichAA posted 07-25-2002 11:28 AM ET (US)     Profile for RichAA  Send Email to RichAA     
Thanks guys!
jimh posted 07-25-2002 12:57 PM ET (US)     Profile for jimh  Send Email to jimh     
By the way, when your mechanic mentioned "backfire" I infer that something happened which caused the pressurization of this valve to become subject to a great deal more reverse pressure than is normal. This may have damaged the operation of the check valve, perhaps stopping it from working entirely or jamming it closed. And this may have lead to your problem.
jameso posted 07-25-2002 02:24 PM ET (US)     Profile for jameso  Send Email to jameso     
'Check valve' they gave you a valve you gave them a check, check?
RichAA posted 07-25-2002 05:41 PM ET (US)     Profile for RichAA  Send Email to RichAA     
Ha! I presume they gave me a valve.

I just wanted to ask about it. They sounded like it was the most normal thing in the world and to myself I'm thinking "So there's some part I've never heard of that can disable me with a backfire that wasn't loud enough for me to recall?"

Plus, I still carry the sting of having been suckered to going off on a snipe hunt back in Boy Scouts and I think it's made me permanently skeptical..... :)

Thanks again,


Landlocked posted 07-29-2002 10:08 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
The common snipe, Gallinago gallinago, actually exists (despite popular opinion). I have actually eaten them - very stringy dark meat.

Don't know why I felt the need to respond but there you have it. The next time someone asks you to go snipe hunting take em' up on it. The little suckers are so fast they are almost impossible to hit.

Now back to whalers.


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