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Re: [GMCnet] Fuel Pump Poll [message #239269] Sun, 09 February 2014 07:56 Go to previous message
Jim Bounds is currently offline  Jim Bounds   United States
Messages: 842
Registered: January 2004
Karma:
Senior Member
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

-------- 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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