I have one of these engines as well. Does anyone have an idea of just
how many times per hour of normal engine operation an X gallon fuel tank
would be circulated through the filters? I burn somewhat less than a
gallon of fuel per hour at 2100 rpm and 5.5 knots with a 55 gal. tank.

I had a professional company polish my fuel this spring. The technician
indicated that an hour of polishing would recycle my fuel three times or
at a rate of roughly 150 gallons per hour.

I'm sure that normal running is much less frequent.

Last week my dock-neighbor (Gulf Star 43' trawler w/dual Perkins 6-cyl)
went on the three hour tour returning after 45 minutes because one of
his engines had quit. HIs filters had clogged and starved his starboard
engine. When he replaced the fuel filter it looked like he had used it
as an oil filter before switching it over to fuel duty. I've never seen
a dirtier fuel filter.

Joe Wood

Steven Shelikoff wrote:
On Sat, 26 Jul 2003 08:47:53 -0400, "Garry Elmer"
wrote:


Greetings!
I was wondering if anyone knew the mechanism with which the Perkins 108-4
returns un-used fuel to the tank?

I installed a new electric fuel pump in our system and set the supply valve
to one tank and the return valve to the other, trying to transfer fuel and
polish it at the same time, with the diesel off. I did not notice any fuel
being transferred so I assumed that the mechanical lift pump was in the way.

I replaced the fuel filter on the diesel yesterday and while bleeding the
system at the low pressure inlet to the high pressure pump, had plenty of
fuel flow from the electric pump. Much more than expected from the looks of
my bilge.

Where does the return fuel line "pick off"? Is there a pressure relief
valve associated with it? Should I be able to transfer fuel by using the
electric fuel pump with the diesel off?


There's a fuel rail on top of the engine that connects the injectors
together. This rail collects the excess fuel and returns it to the
tank. If there's no flow to the injectors, the fuel won't return. If
you want to polish the fuel, you need another return. You can tee it
into the return to the tank from the engine if you want. But you should
have a check valve on it.

Steve