[Alberg30] Diesels, Fuel and Air

[sousa, stephen (ENG)]

Mike,
 
Is the Racor full of fuel when this happens. I have had the same thing
happen on my diesel cars. The o-ring on the lid was not sealing correctly
letting air into the system, the bowl was partially filled.
 
Stephen

-----Original Message-----
From: Mike Lehman [mailto:sail_505 at hotmail.com]
Sent: Wednesday, July 17, 2002 2:13 PM
To: public-list at alberg30.org
Subject: [Alberg30] Diesels, Fuel and Air



Ever since I installed my diesel about 6 years ago, I have had this
re-occurring problem, so I thought I would ask for advice from the list. I
find that, after running the engine for several hours, I get a buildup of
air in the fuel lines and the engine starts to stall and run poorly. The
problem is so frequent and predictable that I keep a 10mm box wrench hanging
next to the engine so I can quickly open the bleed valve on the injector
pump and bleed off the air, then it will run fine for several more hours. It
generally coincides with a change in engine speed. This always happens at
the worst possible times, such as entering Sandy Point State Park between
the Bay Bridge and the rock jetty with a 1-1/2 knt current and 20 knts of
cross-wind while single-handing the boat. It makes you a damn good sailor,
keeps you alert and sometimes scares the s--- out of you. 

I have check everything: replaced the fuel pump, rebuilt the new Racor 500,
keep the filters clean, use biospore, removed and cleaned the tank, removed
the screen from the pickup tube, checked for water and contamination and now
I am running out of ideas. It must be a design problem! My tank is an
aluminum 18 gallon saddle tank mounted outboard in the starboard sail
locker. The lines are all USCG approved rubber fuel lines. The supply is at
the forward part of the tank and provides excellent gravity feed to the
engine below. Next in line is the Racor, then the on-engine filter then the
electric lift pump and finally to the injector pump. This all seems fine and
designed appropriately. The return line connects to the rear of the tank to
a t-fitting which is shared by the vent line. Here's my current
thought....since the engine only burns 1/2 gallon per hour and the fuel pump
feeds much more than that, a lot of fuel is being returned to the tank. Is
it possible that the ret! urned fuel is blocking the vent thereby creating a
vacuum causing the pump to suck harder and drawing in air from an otherwise
air tight system? My thought is to convert the vent/return connection and
make it "vent only". Then "T" the return line into the supply line between
the tank and the Racor filter on the suction side of the pump.

Does anyone have any thoughts on this?

Mike Lehman 

"Gilleleje" #505 

"One can never enter the same river twice. The river is always new; the man
is forever changed."


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