Fuel pump,/flow question, 239 8BA
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Senior User
Joined: Jun 2008
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From: Wilmington Delaware
Fuel pump,/flow question, 239 8BA
I put an electric pump on last year ( among other things ) when I was fishing for ideas to get my 51 running. I am still running a 6V system. I have the line out of tank to pump to pressure regulator to filter to carb. I picked up a new stock mechanical pump for free yesterday. I prefer stock stuff when ever possible. I want to put the new pump on and pick up the flow at/before the regulator and keep the electric pump on for back up but I dont kmow how that would effect the flow? Is it absoluteley nessesary to bypass/remove the fuel pump. My guess is its got to go.
The electric pump is a bit noisy and as you all know a 6V system is always better off with less stress on it. I wont be doing the 12v conversion till fall.
Any thoughts?
The electric pump is a bit noisy and as you all know a 6V system is always better off with less stress on it. I wont be doing the 12v conversion till fall.
Any thoughts?
Fleet Owner
Joined: Jul 2004
Posts: 27,304
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From: NM
Trying to suck through the electric pump isn't a good idea. If you want both, they should be parallel systems, with the electric delivering just downstream (towards the carb) from the stock pump. That way the mech pump's check valves will prevent backflow thru the mech system. See what I mean? Most people who do this just prime the carb with the electric to get the engine started without a lot of cranking.
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Senior User
Joined: Jun 2008
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From: Wilmington Delaware
hat way the mech pump's check valves will prevent backflow thru the mech system. See what I mean?
Do you mean" backflow thru the electric pump"?. I like the idea of priming with the electric pump. As always Thanks Ross
Mountain Pass
Joined: May 2004
Posts: 145
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From: Jonesborough, TN
It depends on what kind of electric fuel pump you have, but many/most of the new ones you can suck right through them with the mechanical pump. My 50 is set up with the two pumps in series and it works fine. I only use the electric for priming and it is available for backup if I the mechanical pump failure or vapor lock. The electric is directly below the tank with a filter.
Some of the older style pumps would require a parallel setup.
Some of the older style pumps would require a parallel setup.
Cargo Master
Joined: Feb 2008
Posts: 2,795
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From: Windermere Valley,B.C. Ca
And in more ways then one, the Carter rotary vane pump is not to used as an auxiliary because the vanes can stop in a position to block off all gas flow. Ask me how I know this and how long it took to figure out what the problem was!
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Senior User
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From: Wilmington Delaware
Nice info fellas, I got this one at NAPA 
. Store Locator | NAPA Online. Looks like its a parallel run.
. Store Locator | NAPA Online. Looks like its a parallel run.
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Post Fiend
Joined: May 2008
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From: Poway, Ca.
John, do you have a starter button, or a start position on your ignition switch?
The reason I ask is because if you use the Electric as a boost pump and the mechanical as the primary, you could run the parellel system like Ross drew up and have the electric automatically turn on when your starter circuit is powered, and automatically go off when the engine starts and the mechanical pump is pumping.
Even if the rotary vanes allow a trickel of gas to back flow, the mechanical pump should still supply enough to the carb as long as the needle valve is open. This kind of set up would be somewhat similar to a HP EFI that stays at pressure and returns gas to the tank that isn't used. You would just need a protective antibackflow valve for the mechanical pump to keep the electric pump from blowing out the mechanical diaphragm out. Make sense?
The reason I ask is because if you use the Electric as a boost pump and the mechanical as the primary, you could run the parellel system like Ross drew up and have the electric automatically turn on when your starter circuit is powered, and automatically go off when the engine starts and the mechanical pump is pumping.
Even if the rotary vanes allow a trickel of gas to back flow, the mechanical pump should still supply enough to the carb as long as the needle valve is open. This kind of set up would be somewhat similar to a HP EFI that stays at pressure and returns gas to the tank that isn't used. You would just need a protective antibackflow valve for the mechanical pump to keep the electric pump from blowing out the mechanical diaphragm out. Make sense?
Posting Guru
Joined: Sep 2004
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From: Sapulpa OK
Why couldn't you leave the stock pump in place, remove the guts from the mechanical (stock) pump, leave the diaphragm in place, remove the pushrod from the engine and plumb the rotary pump with regulator to pump through the stock pump. Nobody would know it wasn't a stock setup and you would maintain your stock appearance
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Senior User
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From: Wilmington Delaware
You got it Julie. It beyond reverb. more like Surfer Rock Reverb. Also trying to keep stress off the old 6V systerm till I convert to 12V and I just want to use the free/new stock pump since the original is toast. Very cool idea fixnair has there I'll say. I have the starter button and ignition/key.The starter button activates the starter but the ignition/key must be on for spark. I want to be able to prime so, as mentioned, I can reduce some cranking to start and then turn off the electric pump once I am running,...but be able to have the auxilery option also. Switch? Of course none of these great options came to me prior to this thread. I love this place!
Last edited by john smith jr; May 2, 2010 at 08:30 AM. Reason: I wanted to edit of course
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Senior User
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From: Wilmington Delaware
Yea Ross, I used the bushings that came with it and it was really buzzin. I looked at every possible contact point, I even wrapped the fuel line with split rubber hose. I also pulled the pump off, cut a square of rubber gasket material, and backed up the mounting plate that holds the rubber bushing and I still hear it. Maybe its because the Panel body is like a steel drum, or maybe it because that sound, in my mind, just dont fit the natural sound vibes the truck puts out. What can i say, it really bugs me