| Re: [GMCnet] Fuel Pump Poll [message #239269] |
Sun, 09 February 2014 07:56  |
Jim Bounds
Messages: 842
Registered: January 2004
Karma: 0
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Senior Member |
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There is deeper thought put into our mod. Â The pump goes before the selector solenoid so we will have an unobstructed "home run" circuit from the main rear tank to the mechanical pump. Â That's what a "sucker" type of pump need to do its best job. Â Only a few electric fuel pumps come with no check valve function the presents an obstruction to fuel flow when off. Â The small Facet pump we use has no check valve so evrn if it ever fails it will not totally stop fuel flow. Â I still though do not want it in the fuel flow when on "main" selection. Â When flipping the system to "aux.", not only do you switch to a different tank and pickup tube you also throw in a pump that pressurizes the fuel system that not only throws fuel at you mechanical pump but also pressurizes the system effectively thanginy the conditions that could cause vapor lock and will effectively destroy the conditions that set up vapor lock and remove that problem form you. Â It works great and not only that you also have a primer system that will help quickly prime the mechanical pump that may have to suck air until it cam pull fuel from your tank. Â Each time I fire up a coach that has been sitting, I prime the mech pump with this system. Â Motor will start easier without all that dry cranking. Â Only use the system when you need it, always leave your coach and drive in "makm" tank selection and yyou do not have to go through all that stuff with fuel shut off pressure switches. Â If yoy still feel you need to protect your coach from yourself, power the circuit off the center terminal on the battery isolator but that really is limiting the positive use of the circuit. Â If you only select it when you need it you will be safe.
Jim Bounds
-------- Original message --------
From: mike foster <mafoster1@bellsouth.net>
Date: 02/08/2014 7:42 PM (GMT-05:00)
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Fuel Pump Poll
pyolet wrote on Fri, 07 February 2014 21:26
> In tank pumps selected with gauge switch. No more hot day, high altitude cavitation issues, even on E10.
>
> W.
Back in 1981 I was rebuilding my brother-in-laws 1975 280/Z engine and while going through the Robert Bentley service manual I noticed a statement about the EFI fuel pump:
"The fuel pump maintains pressure of 37 PSI (that might not be THE number...it has been 33 years), vapor lock is not a problem."
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| Re: [GMCnet] Fuel Pump Poll [message #239319 is a reply to message #239269] |
Sun, 09 February 2014 16:29  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
Not that Jim needs ME to do so but I can vouch for everything he's noted; he installed one of those little Facet pumps in Double
Trouble five years ago and it works GREAT! I use it just like he outlines below.
I do have one recommendation; when driving through the mountains I recommend you fill up with gas JUST before you stop for the night
or the first thing in the morning BEFORE you start climbing. If you don't you can get into a situation where there isn't enough fuel
in the AUX tank when heading up hill for the Facet pump to work. Been there done that!
Below you will find the specs for the pump:
12 VOLT FACET® CUBE FUEL PUMPS
PART #: 40104
MIN - MAX PSI: 1.5 - 4.0
GPH: 25
INLET/OUTLET THREAD SIZE: 1/8-27 NPT
MIN. DRY LIFT: 12"
CHECK VALVE: NO
I did a quick search on the Internet and here's the best price I found ($36.85) and they will ship using USPS.
http://www.aircraftspruce.com/catalog/eppages/facetpumps.php
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: gmccoop
There is deeper thought put into our mod. The pump goes before the selector solenoid so we will have an unobstructed "home run"
circuit from the main rear tank to the mechanical pump. That's what a "sucker" type of pump need to do its best job. Only a few
electric fuel pumps come with no check valve function the presents an obstruction to fuel flow when off. The small Facet pump we
use has no check valve so evrn if it ever fails it will not totally stop fuel flow. I still though do not want it in the fuel flow
when on "main" selection. When flipping the system to "aux.", not only do you switch to a different tank and pickup tube you also
throw in a pump that pressurizes the fuel system that not only throws fuel at you mechanical pump but also pressurizes the system
effectively thanginy the conditions that could cause vapor lock and will effectively destroy the conditions that set up vapor lock
and remove that problem form you. It works great and not only that you also have a primer system that will help quickly prime the
mechanical pump that may have to suck air until it cam pull fuel from your tank. Each time I fire up a coach that has been sitting,
I prime the mech pump with this system. Motor will start easier without all that dry cranking. Only use the system when you need
it, always leave your coach and drive in "makm" tank selection and yyou do not have to go through all that stuff with fuel shut off
pressure switches. If yoy still feel you need to protect your coach from yourself, power the circuit off the center terminal on the
battery isolator but that really is limiting the positive use of the circuit. If you only select it when you need it you will be
safe.
Jim Bounds
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Fuel Pump Poll [message #239366 is a reply to message #239319] |
Mon, 10 February 2014 00:32 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Proper procedure is everything.
Low wing gasoline aircraft have the exact same setup. An electric pump before the mechanical pump. It is a Facet interupter type pump like we have on the Onan.
The procedure is:
1. Prior to starting turn on the electric fuel pump and check the pressure. Turn pump off.
2. Start the engine then check the oil pressure and fuel pressure running just the mechanical pump.
3. Taxi to a run up area and check engine power under load (a run up on mechanical pump only)
4 Pre-take-off check list - turn the electric fuel pump on.
5. After climb out - turn fuel pump off.
6. Pre-landing check list - Turn fuel on.
In any kind of engine related emergency:
1. Electric fuel pump on
2. Carb heat on
3. Mixture full rich
As you can see the electric fuel pump is used solely as a back up device much the same as we use it in the GMC.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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