Subject: [TR] Gas line filter placement.

From: Angelo Graham <[email-masked]>
Date: Mon, 09 Jul 2012 11:44:48 -0400

Hello List:
After rebuilding my carbs (again) and getting them back on the car, I 
was advised to fit an in-line gas filter. I have sourced a generic nylon 
bodied see through type with what appears to be a paper filter inside. 
Was also advised to fit this in-line before the fuel pump to prevent 
damage to the fuel pump valves. I was going to install it before the 
carbs on a convenient stretch of the metal gas line.
Any comments on installing the filter before the fuel pump? Should I 
install another before the pump as well?
Interested in others' experiences.
Thanks for any advice on this one.
Angelo Graham

** [email-masked] **

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From: "Randall" <[email-masked]>
Date: Mon, 9 Jul 2012 10:39:55 -0700

> Any comments on installing the filter before the fuel pump?

I'm sure opinions will vary, but I've heard that running a paper element
filter before the pump can aggravate any tendency towards vapor lock as the
resistance of the filter lowers the pressure slightly.  Likely not enough to
worry about, but I've never seen a car with that configuration as original,
so perhaps there is something to it.

Anyway, after years of running with just the factory sediment bowl and
screen, I finally added a paper element filter at the carbs.  No more "sand"
in the bottom of the float bowls.

-- Randall

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From: Wbeech <[email-masked]>
Date: Mon, 9 Jul 2012 14:17:55 -0500

Electric pump, put it before.  OEM pump can go after.  For $10 i got nice
glass inline filter with a replaceable element. It's nice to be able to see
the fuel and the crud.

Sent from mobile Bill

On Jul 9, 2012, at 10:44 AM, Angelo Graham <[email-masked]> wrote:

> Hello List:
> After rebuilding my carbs (again) and getting them back on the car, I was
advised to fit an in-line gas filter. I have sourced a generic nylon bodied
see through type with what appears to be a paper filter inside. Was also
advised to fit this in-line before the fuel pump to prevent damage to the fuel
pump valves. I was going to install it before the carbs on a convenient
stretch of the metal gas line.
> Any comments on installing the filter before the fuel pump? Should I install
another before the pump as well?
> Unsubscribe/Manage:
http://autox.team.net/mailman/options/triumphs/[email-masked]

---

From: Chris Simo <[email-masked]>
Date: Mon, 9 Jul 2012 15:33:59 -0400

I put my filter in the flex line near the gas tank. My rationale was it's a
big filter and my motorcycle ran fine with a gravity fed fuel system
through an absolutely tiny filter.

I have not had issues other than it filling up with rust.  Nice thing -
it's out of sight. Bad thing - its out of sight so i rarely replace it.....

I can believe a pump would cavitate with a really clogged filter installed
my way.  So far i haven't been inconvenienced by it. ( I now even have a
clean and coated tank... )

---

From: David Templeton <[email-masked]>
Date: Mon, 9 Jul 2012 19:42:40 +0000

Angelo

I added a glass one with replaceable filter to the '3, I found that under
driving it was good, but a little spirited driving actually caused issue.
Mind you I did at that time have the OEM pump and the filter was by the tank (
before the pump )

David

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Angelo Graham
Sent: Monday, July 09, 2012 11:45 AM
To: [email-masked]
Subject: [TR] Gas line filter placement.

Hello List:
After rebuilding my carbs (again) and getting them back on the car, I was
advised to fit an in-line gas filter. I have sourced a generic nylon bodied
see through type with what appears to be a paper filter inside.
Was also advised to fit this in-line before the fuel pump to prevent damage to
the fuel pump valves. I was going to install it before the carbs on a
convenient stretch of the metal gas line.
Any comments on installing the filter before the fuel pump? Should I install
another before the pump as well?
Interested in others' experiences.
Thanks for any advice on this one.
Angelo Graham

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Archive: http://www.team.net/archive
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From: [email-masked]
Date: Tue, 10 Jul 2012 03:17:32 +0000 (UTC)

> Any comments on installing the filter before the fuel pump?

Yes.  Do it.  Especially if it is an electronic fuel pump like a Facet,

Also, mount your Facet as low as possible.  Uncle Jack loses prime now and again, so I'm going to check into a lower mounting.  Real soon now...

> resistance of the filter lowers the pressure slightly.

Stuff and nonsense.

> in the bottom of the float bowls.

If you find that you are getting junk from the fuel pump, yes.

Phil Ethier West Side Saint Paul Minnesota USA
1973 Triumph Stag LE22439UBW "uncle jack", Sapphire Blue
2004 Suburban 8.1, Sport Red, the only automatic of the bunch
2005 Lotus Elise, Bordeaux Red Pearl
2007 Saturn Ion 3 2.4, Berry Red
pethier [at] comcast [dot] net
http://www.flickr.com/photos/pethier
http://www.triumphtransamerica.org.uk
http://www.mnautox.com

---

From: "Randall" <[email-masked]>
Date: Tue, 10 Jul 2012 21:30:02 -0700

> > resistance of the filter lowers the pressure slightly.

Vapor lock happens when the gasoline in the line leading to the pump
vaporizes.  (The lock part comes in because the pump cannot pump vapor very
well.)  The pressure at which the gasoline vaporizes depends on the fuel
blend and fuel temperature. 

A little quick poking around shows that US law restricts gasoline to no more
than 9 psia Reid vapor pressure.  This means (approximately) that it will
start to boil at 100F when the pressure drops below 9 psia.  Since 1
atmosphere is roughly 14.7 psia, that gives us a 5.7 psi margin for pressure
drop in the inlet tube.

But, the vapor pressure goes up rapidly with temperature, and even the fuel
in the tank can easily be hotter than 100F.  I'm too lazy to work out the
equation (and I couldn't find a chart for it), but you can see some typical
curves here:
http://goo.gl/yI6ci
Remember the fuel line goes under the car, where it both gets the hot air
blown back by the radiator fan when sitting stopped in traffic, and heat
from the exhaust system.

And I have seen paper element filters that had over a 5 psi drop at a
reasonable fuel flow.  Granted, that was a sign that they needed to be
changed, but I've never been very good at changing them before they needed
to be changed.  And in probably 300,000 miles in an assortment of TR3s all
with rusty gas tanks and no filter in front of the pump, I have never had a
fuel pump quit because of dirt.

I find it interesting that you have trouble with the Facet pump on uncle
jack.  I've also got a Facet pump in my Stag (the one I drove 5000 miles
round trip to VTR 2005), mounted in the stock location, and it never had any
trouble picking up fuel.  My guess is that you have a leak or restriction on
the inlet side.  Facet pumps don't have check valves, but they should be
able to pick up fuel from at least 24 inches.  Here is a video of one
picking up more than 36":
http://www.youtube.com/watch?v=upZqF7y97h0

-- Randall