On 6-Jan-2004, "Geoffrey Freer" wrote:

I am new to diesel engines, well new to sailing for that matter. I want to
replace both filters on my diesel engine.

By both filters I assume you mean the engine and prefilter. A good idea if
you want to establish a base history of filter changes, you don't know when
they were last changed, it's been a several months, or you know you've got
contaminated fuel and it may have passed through the engine. On my boat I
change the prefilter every 200 hours or 3 months. The engine filter gets
changed every other time I change the prefilter. If you don't have a
prefilter, install oen. It'll pay for itself by keeping the fuel going to
the engine filter cleaner and provide a visual indication (if you install
one with a clear sediment bowl) of the condition of the fuel.

If you're going through the trouble to change the prefilter I'd make sure
the bowl was clean and empty. In my experience, when filters come with
o-rings they you should replace the old ones with the new ones.

I know that air in the system creates problems. Do I fill the filters with
diesel first before reconnection?

I do primarily because the pump that will fill the engine filter is very
inconvenient to use and takes a lot of pumps to fill an empty filter. By
prefilling it with clean fresh fuel I can minimize this effort. A fair
number of prefilters have pumps on them to assist you with that part also.

Do I bleed the filters when connected?

It depends on the engine but in general you would make sure that the air was
out of the fuel system from the prefilter to the high pressure pump.

Do I bleed air one filter at a time?

Again it depends on the engine and their procedure but yes, I do.

I am also replacing the hoses. Do I fill the hoses with diesel before
attempting to start?

If you're replacing the hoses that go from the tank to the engine, you've
added a lot of work. In that situation I'd install a dc powered external
fuel pump between the fuel tank and the prefilter. It will make filling the
empty fuel lines and bleeding the fuel system easier. And making onerous
chores easy insures that you'll do the filter changes when they're due
rather than when they're needed.

I'd carefully replace the hoses (and double clamp them) with approved hose
material for the type of fuel you're using. Then I'd replace the filters,
filling the bowl or filter(s) with clean fuel. Once that was done I'd crack
the bleeder nut on the prefilter, turn on the pump, and with a bucket under
the filter to collect the fuel overflow, run the pump until fuel comes out
of the bleeder and no air is present. I'd then close the bleeder nut on the
prefilter and crack the one on the engine fuel filter. Turn the pump on and
wait for bubble-free fuel to come out of the filter. When that happens you
know there is a good chance no air is present in the fuel system from the
pump to the engine filter.

From then on, I'd do what the engine manufacturer suggests. On my old
Perkind 4-108 diesel, I'd have to crack the input to the high pressure pump
and bleed it before heading on to the injectors.

Good luck and remember safety. Have an extinguisher nearby as well as a good
source of ventillation. Dispose of fuel soaked rags properly and have plenty
of absorbent pads to mop up. And you might as well change the oil and
filters, as well as the air filter, check the antisiphon valve, and give the
engine a general checkout.

rws

Any help, advice or suggestion would be
appreciated. Geoff