MD6A: Need to cut off fuel supply before changing fine filter

[Vega1447]

Hi all.
The subject says it all(most).
I've got a replacement fine fuel filter from local diesel parts place
and plan to change filter at weekend.

It occurred to me that as my fuel tank is in cockpit locker the fuel
source is slightly higher than the location of the filter.

Unfortunately I dont (yet) have a fuel cutoff tap.

Will I just get some drips that I can collect in a basin or will I get
a lot of diesel flowing out when I remove the old fuel filter?

(I could "kink" the supply line as a poor man's fuel cutoff tap?)

Thanks,

John

Vega 1447 Breakaway

 

[vegatern]

I have a similar setup. The fuel tank is in the lazarette, above
the engine. If your system is the same as mine fuel needs to pass the
lift pump before the fine filter, and won't flow without the lift pump
running. I think you will need to prime the fine filter with the lift
pump after you have installed the new filter. You may want to fill
the new filter with clean fuel before screwing in place because it
takes a long time to fill it with the lift pump handle, then open the
bleed screw on the fine filter to clear the remaining air. You may
also need to bleed air at the top end of the injector tubes, where
they enter the engine, because fuel will probably run out the tubes
when you remove the fine filter.
If you also replace the filter in the water separator filter,
which in my system is below the tank and before the lift pump, you may
find it difficult to fill the supply line between the tank and the
filter. In my case the pick up is at the bottom of the tank but exits
at the top, then drops to the Racor filter. Removing the filter traps
air at the top of the loop making it difficult to dislodge. An
electric fuel pump at the tank would solve the problem but I found it
simpler to cut the line at the top of the tank and add a bulb type
fuel primer, the kind that are used on outboard engine gas tanks. It
is a simple matter to fill the Racor with the primer bulb, pumping
until no air shows. I am not a mechanic, learning as I go, others may
have better suggestions, but removing the fine filter did not result
is a flood of fuel.
Good luck, Craig Tern#1519

 

[Vega1447]

Thanks Craig,
my setup is I think very similar - tank is in port locker; fuel feed
pipe runs aft then passes through bulkhead into drive shaft
compartment under cockpit and forward to water trap filter, then to
fuel feed pump and then to fine filter.

I take your point about fine filter - as it is downstream of the
engine-driven feed pump it should not be a problem removing the fine
filter & replacing. Priming the new filter with diesel sounds like a
good idea.

But: as with my lubricating oil filter, I find it impossible to remove
the fine filter..

I spent an hour today trying to remove oil filter using a rubber
version of a "chain spanner" - I couldnt get the damn thing to turn.

In the end I used the Homer Simpson method, poke holes with
screwdriver and twist.. Even then it took a lot of incremental steps.
And a lot of oil splashes..

Is there a better way to remove the fine filter? It is much more
accessible than the oil filter but my "rubber chain spanner" didnt
budge it.

Finally: I tried to open fuel feed pump cover to clean the gauze
pre-filter (as in MD6A manual). I removed the hex-headed bolt that
secures the top of feed pump and fuel started to come out though the
bolt hole. But how to get the cover off???? I suspect it has never
been removed - the paint seems intact.

Maybe with a water trap before the fuel feed pump there is no
pre-filter in the fuel feed pump?

Suggestions welcome!

Thanks again,

John

Vega 1447 Breakaway

 

[coonhopper2000]

Anybody know where I can get wiring diagram for 1973 MD6A with dynastarter and alternator. Boat vandalized and robbed of all engine instruments and ignition. Vega# 2137 "Puffin" Thanks, pat

vegatern vegatern@... wrote: I have a similar setup. The fuel tank is in the lazarette, above
the engine. If your system is the same as mine fuel needs to pass the
lift pump before the fine filter, and won't flow without the lift pump
running. I think you will need to prime the fine filter with the lift
pump after you have installed the new filter. You may want to fill
the new filter with clean fuel before screwing in place because it
takes a long time to fill it with the lift pump handle, then open the
bleed screw on the fine filter to clear the remaining air. You may
also need to bleed air at the top end of the injector tubes, where
they enter the engine, because fuel will probably run out the tubes
when you remove the fine filter.
If you also replace the filter in the water separator filter,
which in my system is below the tank and before the lift pump, you may
find it difficult to fill the supply line between the tank and the
filter. In my case the pick up is at the bottom of the tank but exits
at the top, then drops to the Racor filter. Removing the filter traps
air at the top of the loop making it difficult to dislodge. An
electric fuel pump at the tank would solve the problem but I found it
simpler to cut the line at the top of the tank and add a bulb type
fuel primer, the kind that are used on outboard engine gas tanks. It
is a simple matter to fill the Racor with the primer bulb, pumping
until no air shows. I am not a mechanic, learning as I go, others may
have better suggestions, but removing the fine filter did not result
is a flood of fuel.
Good luck, Craig Tern#1519

 

[shanachie70]

Pat;
I see the diagram didn't attach. I have uploaded it to the files section, for anyone who may need it.

Don

 

[brockhaus77]

Hi,

I don't know whether you already changed your fine filter. Maybe
it's o.k. to remove it without stopping the fuel flow, but I don't think
the fuel lifter pump is a perfect barrier. In my setup (tank in the
starboard lazarette) I have a simple valve (quarter-turn to shut off)
in line with one of those "outboard fuel lines" with built-in bulb. So for
any filter change, I first close that valve, then remove BOTH the RACOR
and the fine filter. I can refill the RACOR (which is slightly lower than the
tank) just by letting gravity do its work (as long as the tank is nearly full).
To refill the fine filter, I use the bulb (squeeze gently a couple of times).
This works fine, so that shows me that with a little pressure the fuel
CAN pass by the lifter pump. I have a bleeding nipple at the top of the fine
filter, and I continue squeezing until fuel appears. That's it.
To remove the filter, I ordered a special fllter wrench (it was a different
size from that for standard oil filters ) - it's a steel band that goes around
the filter and that you can tension by twisting the handle. That usually gets
a good grip. Should be available in car supply stores.

- Sebastian (VegaLyra 1060)

 

[Vega1447]

Hi all and thanks for advice on cutting off fuel when replacing fine fuel
filter.

As subject suggests - I seem to have an airlock after fuel filter - I bled
system at fine filter and plenty of fuel came out.

I tried the usual technique to clear out the air in fuel feed lines by
loosening nuts at injectors then cranking engine (I first used starter
motor then to avoid damaging starter I hand-cranked.)

After 10 minutes no joy = no fuel at injectors.

I saw an old post (from Steve Birch) suggesting bleeding the injector pump
itself - manual doesnt mention this.

Steve suggested loosening a bolt on forward face of the injector pump.

The engine in question was a MD7A - mine is a MD6A; should this trick also
work for an MD6A?

Where exactly is the bolt?

Strange its not mentioned in the owners or workshop.

BTW I think my injector pump is Bosch - it looks like the one in the
workshop manual - perhaps only CAV pumps can be bled??

Thanks for any advice,

JohnJohn A. Kinsella Ph: +353-61-202148 (Direct)
+353-61-333644 x 2148 (Switch)
Mathematics Dept. e-mail: John.Kinsella@...
University of Limerick FAX: +353-61-334927
IRELAND Web: John Kinsella's Website

 

[vegatern]

I believe that the MD7A is just a bit larger bore than the MD6A.
The manual I have is for a 6A with a supplement for the 7A and I
don't see much difference in the basic layout. I did bleed the
injector lines at their lower end first and then the higher end.
Follow the lines from the injectors back down to where they attach to
the bow face of the injector pump and there should be a nut on the
fuel line, like a flare fitting, there. Try bleeding them there and
then at the top end of the lines. I can't remember if I used the the
hand crank or just the lift pump but either should work. Sebastian's
suggestion about using the primer bulb to fill the fine filter would
eliminate the chance of getting dirt in the fuel. I will try that
next time.
Craig Tern #1519

 

[Vega1447]

Thanks Craig.
As you and Steve Birch have independently made the same suggestion - it
must be true. :-|

Much appreciated - it was very frustrating (but good exercise)
hand-cranking the engine watching for the diesel to appear at the injectors.

All the best,

John

Vega 1447 Breakaway

vegatern wrote:

 

[groundhogyh]

I think I have the same setup as you do.
I bled mine at the fine filter as shown in the manual, then I unscrewed the connection at the top of the injectors and used the starter to crank the engine for awhile (remove compression from engine using lever). It didn't take long for me to see fuel at the injectors. Probably less than one minute. I have the electric fuel pump on my system.
roy
#1813

 

[Vega1447]

Thanks Roy.

I think where I went wrong was that I didnt fully bleed the system at
the fine filter - it was taking a long time with the finger pump - I
should have rotated the flywheel to a different position before resuming
as the manual suggests.

Then I started the engine and it ran for 15 secs which used up the fuel
in the line; creating an airlock in the injector pump - clever of me,
wasn't it?

Bleeding at the injectors didnt clear the airlock in the pump. 10
minutes of hand cranking!!

Steve B and vegatern both suggested bleeding the connector on the
forward face of the injector pump - I'll try tomorrow.

Fingers crossed and thanks for advice,

John

groundhog wrote: