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 Post subject: fuel check valve
PostPosted: 29 May 2013 19:47 
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Skipper

Joined: 21 Oct 2006 18:12
Posts: 325
I have installed a built in fuel polishing system along with a few more filters on my W40. The problem I am having is that the Walbro 6802 is having trouble polishing properly due (I believe) to the amount of vacuum required from the fuel tank. If I take a feed from a jerry can it works fine. The pick up tube (no screen) in the main tank is about 3/8", it goes to check valve with a spring which reduces it to about 1/8", then thru a shut off valve and finally into 1/4" copper. In the W46 technical manual it says not to use the spring type check valve because of increased vacuum required and that it is hard on the lift pump. I see nothing like this written in the W40 or W50 manual. So I think this check valve is reducing my flow (increased vacuum) too much for my polishing system yet it works fine for the engine. My thought is to replace this check valve with a more modern (less resistance to opening and a larger diameter (1/4"?) and hopefully this will fix it. Anyone see any issues with this or had similar problems?

Richard


 
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 Post subject: Re: fuel check valve
PostPosted: 30 May 2013 06:05 
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Skipper

Joined: 29 Dec 2006 09:38
Posts: 656
No check valves in W50 so I can't comment on that, but you might check your tank vent. I had a lot of trouble on a passage with negative tank pressure and finally found the problem was that my vent was blocked by a spider nest. Engine ran with fuel cap off, would run for a period with it on, but shut down as negative pressure built.

I do not see the point of a check valve in a T37 as the engine is mostly below fuel level any way, but you appear to have an different engine, so maybe this is a requrement on yours. Also, I once had problems with the screen clogging on the pick up tube in the tank. Several mechanic friends advised me to remove it. Apparently these screens were common in the 70's and 80's production boats. I have had no problems with anything in the last 15 years since removing it.


 
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 Post subject: Re: fuel check valve
PostPosted: 30 May 2013 06:58 
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Skipper

Joined: 21 Oct 2006 18:12
Posts: 325
Hmm, strange that the W50 doesn't have it yet the W40 does. It is the first horizontal threaded pipe piece from where the pickup comes out of the tank, my second piece is the fuel shut off valve. You may not even know the check valve is there unless you take this all apart. I have checked the vent line and it is clear, but I have had it plugged before.

Richard


 
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