That would require me to have 2 pretty much independent polishing
systems. I don't really have the room for that and the extra
expense would be hard to justify.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Tue, 2 Dec 2003 23:41:45 -0500, "Doug Dotson" wrote:

That may be true, and as long as it stays there the engine still
runs fine. If it does get shaken up, the a polishing system will
do its job while lessing the crud going through the engine filtering
system. Once initial polishing is done, I will be alternating between
tanks. One running while the other polishing. Getting things shaken
up is the best thing I can hope for.

Why not just always leave the polishing system in-line? Allow for a
bypass to change a filter or if it develops a vacuum leak, but other
then that, there's nothing wrong with always using "just polished" fuel.

Steve

Pretty sure I posted a link early in this conversation that shows a diagram
of a polishing system based on a GCF F-1 filter that allows either polishing
or running with the F-1 as the first filter before going into the Racor
while running. If I didn't, or you can't find it, here it is again:
http://www.trawlerworld.com/features_06.htm

"Doug Dotson" wrote in message
...
That would require me to have 2 pretty much independent polishing
systems. I don't really have the room for that and the extra
expense would be hard to justify.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Tue, 2 Dec 2003 23:41:45 -0500, "Doug Dotson" wrote:

That may be true, and as long as it stays there the engine still
runs fine. If it does get shaken up, the a polishing system will
do its job while lessing the crud going through the engine filtering
system. Once initial polishing is done, I will be alternating between
tanks. One running while the other polishing. Getting things shaken
up is the best thing I can hope for.

Why not just always leave the polishing system in-line? Allow for a
bypass to change a filter or if it develops a vacuum leak, but other
then that, there's nothing wrong with always using "just polished" fuel.

Steve

On Wed, 3 Dec 2003 17:21:58 -0500, "Doug Dotson" wrote:

That would require me to have 2 pretty much independent polishing
systems. I don't really have the room for that and the extra
expense would be hard to justify.

I guess I don't understand your system. Why would it require two
independent polishing systems? Even with a single set of filters (GCF
fillowed by Racor) you can use valves and piping to plumb the thing any
way you want.

Steve

"Steven Shelikoff" wrote in message
...
On Tue, 2 Dec 2003 23:41:45 -0500, "Doug Dotson" wrote:

That may be true, and as long as it stays there the engine still
runs fine. If it does get shaken up, the a polishing system will
do its job while lessing the crud going through the engine filtering
system. Once initial polishing is done, I will be alternating between
tanks. One running while the other polishing. Getting things shaken
up is the best thing I can hope for.

Why not just always leave the polishing system in-line? Allow for a
bypass to change a filter or if it develops a vacuum leak, but other
then that, there's nothing wrong with always using "just polished" fuel.

Steve

Steve,

I understood that you were suggesting that I leave the polishing system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well. So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 17:21:58 -0500, "Doug Dotson" wrote:

That would require me to have 2 pretty much independent polishing
systems. I don't really have the room for that and the extra
expense would be hard to justify.

I guess I don't understand your system. Why would it require two
independent polishing systems? Even with a single set of filters (GCF
fillowed by Racor) you can use valves and piping to plumb the thing any
way you want.

Steve

"Steven Shelikoff" wrote in message
...
On Tue, 2 Dec 2003 23:41:45 -0500, "Doug Dotson"
wrote:

That may be true, and as long as it stays there the engine still
runs fine. If it does get shaken up, the a polishing system will
do its job while lessing the crud going through the engine filtering
system. Once initial polishing is done, I will be alternating between
tanks. One running while the other polishing. Getting things shaken
up is the best thing I can hope for.

Why not just always leave the polishing system in-line? Allow for a
bypass to change a filter or if it develops a vacuum leak, but other
then that, there's nothing wrong with always using "just polished"
fuel.

Steve

On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson" wrote:

Steve,

I understood that you were suggesting that I leave the polishing system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well. So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install vacuum
gauges, one before the GCF filter, one between the GCF and the Racor and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return lines.
Then there's a T where the engine return and the polishing system return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve

Steve,

Just a quick reply since I'm about ready to hit the sack. I think you are
saying that the polishing system should be something that can be switched
inline on the way to the engine. That amounts to just more pre-engine
filtering.
What I want is a system that can recirculate fuel independent of the engine
system. From what I gather, recirculating fuel through a filtering system
will
result in clean fuel so that the engine system will not be stressed (lift
pump).
Also, much crud is built up while just sitting in the slip or on the hard
over
the winter. Better to clean it up prior to offering it up to the engine than
hitting the engine filters all at once.

Your ACSII schematic came across totally skewed. That is a problem
with proportional fonts and TABs

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson" wrote:

Steve,

I understood that you were suggesting that I leave the polishing system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well. So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install vacuum
gauges, one before the GCF filter, one between the GCF and the Racor and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return lines.
Then there's a T where the engine return and the polishing system return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve

On Wed, 3 Dec 2003 23:44:05 -0500, "Doug Dotson" wrote:

Steve,

Just a quick reply since I'm about ready to hit the sack. I think you are
saying that the polishing system should be something that can be switched
inline on the way to the engine. That amounts to just more pre-engine
filtering.
What I want is a system that can recirculate fuel independent of the engine
system. From what I gather, recirculating fuel through a filtering system
will
result in clean fuel so that the engine system will not be stressed (lift
pump).
Also, much crud is built up while just sitting in the slip or on the hard
over
the winter. Better to clean it up prior to offering it up to the engine than
hitting the engine filters all at once.

With the system I described below, what you can do is, while the engine
is not running (there are long periods when it's off, right?) shut off
the valve to the engine intake. Then you have your system that can
recirculate fuel through the filtering system and clean the fuel in the
tank without it going to the engine. Leave the pump on for a few days
or until the filters clog, whichever comes first, before opening the
valve to the engine. Then open the engine valve to run it and it'll get
the freshest filtered fuel possible because it's drawing it right from
the polishing system.

Of course, the disadvantage of doing it this way is that if you don't
install polishing system bypass valves, you have to run the walbro pump
whenever you're running the engine. I've found that to be not all that
much of a disadvantage and the advantage is that fuel is being polished
whenever the engine is running. You can always wire it into the
ignition switch with a double solenoid relay so that the pump can be
controlled via the ignition switch or another switch with a 12 hour
timer so you can set it and leave the boat and it'll turn off on it's
own after running for 12 hours.

There sre so many different ways you can plumb the thing. The more
flexability you want, the more valves and piping you need. The
disadvantage to making it too flexable is that it becomes too complex
and prone to operator error as well as developing a vacuum leak
somewhere.

Your ACSII schematic came across totally skewed. That is a problem
with proportional fonts and TABs

I know. I didn't use tabs though, just spaces. So if you cut'n'paste
the schematic into a word processor and choose a fixed width font it'll
look fine.

Steve

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson" wrote:

Steve,

I understood that you were suggesting that I leave the polishing system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well. So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install vacuum
gauges, one before the GCF filter, one between the GCF and the Racor and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return lines.
Then there's a T where the engine return and the polishing system return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve

Good suggestions. I'll try and clean up the schematic and take a
closer look at it.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 23:44:05 -0500, "Doug Dotson" wrote:

Steve,

Just a quick reply since I'm about ready to hit the sack. I think you are
saying that the polishing system should be something that can be switched
inline on the way to the engine. That amounts to just more pre-engine
filtering.
What I want is a system that can recirculate fuel independent of the
engine
system. From what I gather, recirculating fuel through a filtering system
will
result in clean fuel so that the engine system will not be stressed (lift
pump).
Also, much crud is built up while just sitting in the slip or on the hard
over
the winter. Better to clean it up prior to offering it up to the engine
than
hitting the engine filters all at once.

With the system I described below, what you can do is, while the engine
is not running (there are long periods when it's off, right?) shut off
the valve to the engine intake. Then you have your system that can
recirculate fuel through the filtering system and clean the fuel in the
tank without it going to the engine. Leave the pump on for a few days
or until the filters clog, whichever comes first, before opening the
valve to the engine. Then open the engine valve to run it and it'll get
the freshest filtered fuel possible because it's drawing it right from
the polishing system.

Of course, the disadvantage of doing it this way is that if you don't
install polishing system bypass valves, you have to run the walbro pump
whenever you're running the engine. I've found that to be not all that
much of a disadvantage and the advantage is that fuel is being polished
whenever the engine is running. You can always wire it into the
ignition switch with a double solenoid relay so that the pump can be
controlled via the ignition switch or another switch with a 12 hour
timer so you can set it and leave the boat and it'll turn off on it's
own after running for 12 hours.

There sre so many different ways you can plumb the thing. The more
flexability you want, the more valves and piping you need. The
disadvantage to making it too flexable is that it becomes too complex
and prone to operator error as well as developing a vacuum leak
somewhere.

Your ACSII schematic came across totally skewed. That is a problem
with proportional fonts and TABs

I know. I didn't use tabs though, just spaces. So if you cut'n'paste
the schematic into a word processor and choose a fixed width font it'll
look fine.

Steve

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson"
wrote:

Steve,

I understood that you were suggesting that I leave the polishing
system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well.
So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes
to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install
vacuum
gauges, one before the GCF filter, one between the GCF and the Racor
and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return
lines.
Then there's a T where the engine return and the polishing system
return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also
use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve

Good suggestions. I'll try and clean up the schematic and take a
closer look at it.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 23:44:05 -0500, "Doug Dotson" wrote:

Steve,

Just a quick reply since I'm about ready to hit the sack. I think you are
saying that the polishing system should be something that can be switched
inline on the way to the engine. That amounts to just more pre-engine
filtering.
What I want is a system that can recirculate fuel independent of the
engine
system. From what I gather, recirculating fuel through a filtering system
will
result in clean fuel so that the engine system will not be stressed (lift
pump).
Also, much crud is built up while just sitting in the slip or on the hard
over
the winter. Better to clean it up prior to offering it up to the engine
than
hitting the engine filters all at once.

With the system I described below, what you can do is, while the engine
is not running (there are long periods when it's off, right?) shut off
the valve to the engine intake. Then you have your system that can
recirculate fuel through the filtering system and clean the fuel in the
tank without it going to the engine. Leave the pump on for a few days
or until the filters clog, whichever comes first, before opening the
valve to the engine. Then open the engine valve to run it and it'll get
the freshest filtered fuel possible because it's drawing it right from
the polishing system.

Of course, the disadvantage of doing it this way is that if you don't
install polishing system bypass valves, you have to run the walbro pump
whenever you're running the engine. I've found that to be not all that
much of a disadvantage and the advantage is that fuel is being polished
whenever the engine is running. You can always wire it into the
ignition switch with a double solenoid relay so that the pump can be
controlled via the ignition switch or another switch with a 12 hour
timer so you can set it and leave the boat and it'll turn off on it's
own after running for 12 hours.

There sre so many different ways you can plumb the thing. The more
flexability you want, the more valves and piping you need. The
disadvantage to making it too flexable is that it becomes too complex
and prone to operator error as well as developing a vacuum leak
somewhere.

Your ACSII schematic came across totally skewed. That is a problem
with proportional fonts and TABs

I know. I didn't use tabs though, just spaces. So if you cut'n'paste
the schematic into a word processor and choose a fixed width font it'll
look fine.

Steve

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson"
wrote:

Steve,

I understood that you were suggesting that I leave the polishing
system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well.
So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes
to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install
vacuum
gauges, one before the GCF filter, one between the GCF and the Racor
and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return
lines.
Then there's a T where the engine return and the polishing system
return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also
use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve

On Wed, 3 Dec 2003 23:44:05 -0500, "Doug Dotson" wrote:

Steve,

Just a quick reply since I'm about ready to hit the sack. I think you are
saying that the polishing system should be something that can be switched
inline on the way to the engine. That amounts to just more pre-engine
filtering.
What I want is a system that can recirculate fuel independent of the engine
system. From what I gather, recirculating fuel through a filtering system
will
result in clean fuel so that the engine system will not be stressed (lift
pump).
Also, much crud is built up while just sitting in the slip or on the hard
over
the winter. Better to clean it up prior to offering it up to the engine than
hitting the engine filters all at once.

With the system I described below, what you can do is, while the engine
is not running (there are long periods when it's off, right?) shut off
the valve to the engine intake. Then you have your system that can
recirculate fuel through the filtering system and clean the fuel in the
tank without it going to the engine. Leave the pump on for a few days
or until the filters clog, whichever comes first, before opening the
valve to the engine. Then open the engine valve to run it and it'll get
the freshest filtered fuel possible because it's drawing it right from
the polishing system.

Of course, the disadvantage of doing it this way is that if you don't
install polishing system bypass valves, you have to run the walbro pump
whenever you're running the engine. I've found that to be not all that
much of a disadvantage and the advantage is that fuel is being polished
whenever the engine is running. You can always wire it into the
ignition switch with a double solenoid relay so that the pump can be
controlled via the ignition switch or another switch with a 12 hour
timer so you can set it and leave the boat and it'll turn off on it's
own after running for 12 hours.

There sre so many different ways you can plumb the thing. The more
flexability you want, the more valves and piping you need. The
disadvantage to making it too flexable is that it becomes too complex
and prone to operator error as well as developing a vacuum leak
somewhere.

Your ACSII schematic came across totally skewed. That is a problem
with proportional fonts and TABs

I know. I didn't use tabs though, just spaces. So if you cut'n'paste
the schematic into a word processor and choose a fixed width font it'll
look fine.

Steve

"Steven Shelikoff" wrote in message
...
On Wed, 3 Dec 2003 21:10:23 -0500, "Doug Dotson" wrote:

Steve,

I understood that you were suggesting that I leave the polishing system
running while running the engine. Since I have 2 tanks it seems to me
to require two polishing systems to keep polishing while running. The
system I have designed allows me to polish either of the two tanks
at any time and run the engine out of either tank at any time as well. So
I can polish the same one I am running out of if I wish. I guess the
choice of which to polish while running is up for grabs.

I think I'd route it so that I can route either tank to the polishing
system then 'T' the polishing system to the engine and the return to
either tank. Just make sure you're returning to the same tank you're
drawing from. A simplified version (without bypass plumbing which is a
pain to draw) looks something like this: (view with fixed point font
like courier)

-------------- /--------------------------T---------|
| Y select / return to tanks | |
---------- | --------------- |
| | |(to tank 2) | check valve | |
| Tank 1 | --------------- |
| |---------- ------------- | |
---------- | | Polishing | -------- | ----------
|from | filters | | | | \ | |
Y select /----| with |-| Pump |-T- \-| Engine |
---------- /tanks| bypassing | | | | |
| | | ------------- -------- ----------
| Tank 2 | |
| |----------
---------- out

If the above ascii drawing looks horrible, sorry. But basically, the
supply from both tanks goes to a Y valve which feeds either to the
polishing filters. That's where you'd put the bypass valves so you can
go around any filter (GCF or Racor). Then to a T where one side goes to
a shutoff valve then to the engine. The shutoff valve is so that you
can turn off fuel to the engine while you're priming the system after
changing filters so air won't get in the engine. You can also plumb it
so that the engine can draw from the tanka bypassing the filters so you
can prime them and run the engine at the same time if that's a
requirement. I didn't care about that since I don't run the engine all
that much (sailboat.) Also not shown is that you want to install vacuum
gauges, one before the GCF filter, one between the GCF and the Racor and
one after the Racor before the Walbro pump. Any difference more than a
few psi across a filter means it's time for an element change.

The other side of the T goes to a check valve. That's there so that if
the electric pump fails the engine won't suck air from the return lines.
Then there's a T where the engine return and the polishing system return
join and go to another Y valve to select where to return the fuel to.
Just make sure both Y valves are in the same position. You can also use
this as a fuel transfering pump if you want to, by putting the Y valves
in different positions. But be careful you don't overflow the tank
being filled.

Steve