Fuel pump pipe
Logistics Pro
Joined: Jul 2016
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From: Swan River Valley M.B Can
Not sure about that one there should be no fuel on the top ( mechanical ) part of the pump . It looks to be vacuum but I am not sure what it's purpose would be . I'm sure some one will chime in that knows .
Logistics Pro
Joined: Nov 2006
Posts: 3,663
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From: Fallon,NV & Bainbridge OH
Don't know why they put a fitting there but either that side or the other needs to be vented so don't cap it off unless the other side is open. The only thing I can think of is who ever did it may have had a diaphragm failure in the past that sprayed fuel all over, possibly resulting in a engine fire, so they put that in so they could run a line away from the engine in the event of a failure again.
Laughing Gas
Joined: Mar 2004
Posts: 989
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From: australia
How can it be a return line , it's going to the back of the diaphragm and would just add fuel to the crank case .
It's just a breather so don't plug it .
It's just a breather so don't plug it .
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Logistics Pro
Joined: Nov 2006
Posts: 3,663
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From: Fallon,NV & Bainbridge OH
Bob, now that you mention I recall these in marine applications but not as a "return" but to vent outside the the engine compartment in enclosed hull boats to avoid fuel vapor build up to prevent explosions.
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Logistics Pro
Joined: Sep 2014
Posts: 4,920
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From: Bothell & Silverdale, WA
Geez! Ok, you don't have to plug it. Some applications will have a return line to the tank. This video shows a Mercruiser that has the return back to the carb. Note the yellow line.
I see a syntax error here, and further explanation is necessary. RETURN/VENT FOR CRANKCASE VAPORS!
I see a syntax error here, and further explanation is necessary. RETURN/VENT FOR CRANKCASE VAPORS!
Believe Nothing
Joined: Jun 2004
Posts: 7,512
Likes: 394
From: W. Central FL.
If memory serves me right, marine applications require a fuel return so if the pump malfunctions, any fuel would be returned to the tank or to the carburetor. You sure don't want a fuel fume build up in the bilge.
Logistics Pro
Joined: Sep 2014
Posts: 4,920
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From: Bothell & Silverdale, WA
Quite correct. Automotive fuel pumps are vented to the atmosphere. Although in the event of a diaphragm failure most fuel would still be dumped into the crankcase because the top portion of the pump isn't isolated from the crankcase. In marine applications this is a Coast Guard and ABYC requirement.
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olddawg
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Jun 23, 2002 09:18 PM