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Old 03-02-2021, 06:49 PM   #1
Slowmotoring
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Default Fuel pump installation suggestions

I recently purchased a weber downdraft, a 6v carter fuel pump and a fuel pressure regulator. I guess my first question is (and i should have asked before buying it), do i really need a fuel pump for the weber carburetor or will gravity flow enough fuel? Since i think i will probably need the fuel pump based on what i have read on other threads. Im wondering if anyone has suggestions on wiring the fuel pump. I will be adding a inline fuse (still need to find out how many amps this pump should be drawing). I plan on running the power through a relay controlled by either a toggle switch or the ignition switch. I like the simplicity of the pump being tied in with the ignition switch but i read on another thread that the gentleman was turning off his fuel pump before turning off the motor so the carburetor wouldnt flood the motor. Pretty sure a properly adjusted carburetor shouldn’t be flooding the motor while sitting, but that is why im asking for suggestions. Any thoughts?
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Old 03-02-2021, 08:06 PM   #2
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Default Re: Fuel pump installation suggestions

I run a fuel pump with 1-2 lb pressure. I have a 15 amp fuse, and pump comes on with my ignition switch. You are correct as long as your float is not sticking there is no reason to be shutting the fuel pump off before hand. Really zero issues.
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Old 03-02-2021, 11:08 PM   #3
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Default Re: Fuel pump installation suggestions

I would strongly suggest you also install an inertia switch in case you have an accident. In the case of an accident, you want the fuel pump to automatically shut off. Modern cars with electric fuel pumps are equipped this way. There are inertia switches made specifically for this application. A few years back, a local Model A owner and his wife were returning from dinner one summer evening. The car had a Weber carb and an electric fuel pump. He passed out while going down the road and veered off and hit a tree head on at speed. The engine was displaced to the rear and the fuel line was severed. The fuel pump kept running and the fuel from the broken fuel line ignited and the whole car erupted in flame. The pump kept running and fed more fuel into the fire. Neither occupant was able to exit the car resulting in 2 deaths.

I am very cautious when running electric fuel pumps full time for this very reason. I have electric fuel pumps on my early flat head V-8's so I can prime the carb after the car has sat for a time before cranking the engine. This saves a lot of battery as I am still running 6 volts. The pump is wired thru a momentary switch so I have to have my finger on it to energize the electric pump. Once running, the engine runs on the original mechanical pump.

Something to think about.

Chris W.

Last edited by CWPASADENA; 03-02-2021 at 11:11 PM. Reason: TYPO
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Old 03-03-2021, 07:12 AM   #4
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Default Re: Fuel pump installation suggestions

Both Humperhill and CW in Pasadena have good suggestions. Here is what I have.

I have the Weber carburetor and a fuel pump. My fuel pump is wired to the ignition switch. I make it a habit to turn off the fuel valve under the tank and let the carb run dry when I am going to park the car for more than a few hours. I always turn off the fuel valve even if I don't run the carb dry. Force of habit I guess.

My fuel pump is mounted between the fitting on the bottom of the gas tank and the sediment bulb on the firewall. That makes for a clean installation inside the engine compartment.

I use a 15 amp fuse. I have a fuse block that is mounted to the firewall on the engine side where it is very accessible. It is mounted with magnets so there are no additional holes drilled in the firewall.

Several people run the Weber without a pump but I have been told that there may be a problem when the tank is low.
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Old 03-03-2021, 07:51 AM   #5
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Default Re: Fuel pump installation suggestions

Hopefully, I have attached a picture of a fuel pump setup for the Model A that I would like to know more about. I saw this on the internet. If not, I will try again.

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Old 03-03-2021, 08:08 AM   #6
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Default Re: Fuel pump installation suggestions

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If you are installing an electric pump, you should investigate this FP controller, it makes installation simple, and they work great. https://www.revolutionelectronics.co...Fuel_Pump.html
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Old 03-03-2021, 11:42 AM   #7
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Default Re: Fuel pump installation suggestions

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Hopefully, I have attached a picture of a fuel pump setup for the Model A that I would like to know more about. I saw this on the internet. If not, I will try again.

John
John - That is an old school mechanical (diaphragm) fuel pump. Was very common on carburetor engines, rebuilding one was a standard lesson in high school auto shop (anyone else remember high school auto shop?). They went by the wayside in favor of electric fuel pumps with the advent of fuel injection (you need to have fuel pressure at start to feed EFI, mechanical pumps won't supply pressure until the engine is running). I had one on a boat I bought in the '80s but otherwise haven't seen one of those in years. I doubt you could easily find parts for them any more.

Looks to me that in the transition housing there is a lobed shaft that feeds off the timing gear, and that lobe is what cycles the arm on the pump. Pump output is proportional to engine speed. In theory should work fine.

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Old 03-03-2021, 09:03 PM   #8
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Default Re: Fuel pump installation suggestions

Thanks for the tip on the inertia switch. I will look into that.
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Old 03-03-2021, 09:10 PM   #9
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Default Re: Fuel pump installation suggestions

Great feedback. Thank you!
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Old 06-01-2021, 06:50 PM   #10
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Default Re: Fuel pump installation suggestions

I finally got everything installed, and it almost works! I have the relay coil wired to my ignition switch. When i turn the key on the pump runs great. Once i start the car, the relay starts clicking quickly. When i bring up the rpm’s the clicking slows and stops once i get to a certain rpm. Let off of the gas and the clicking comes back. Any ideas? Im getting to the point i think a toggle switch hidden somewhere will work just fine.
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Old 06-01-2021, 06:56 PM   #11
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Default Re: Fuel pump installation suggestions

I just removed the coil wire going to my ignition switch and hooked it straight to the battery. No clicking at anytime wether running or not. Im thinking some kind of electrical noise issue with the wire being attached with the condenser wire.
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Old 06-01-2021, 07:31 PM   #12
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Default Re: Fuel pump installation suggestions

Are you sure you are not just hearing the fuel pump clicking as it is pumping. Mine is mounted right behind my seat on my speedster, and when I first turn ot on it clicks fast, then as the line fills it slows. or stops.
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Old 06-01-2021, 08:16 PM   #13
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Default Re: Fuel pump installation suggestions

Definitely the relay. I can feel it clicking.
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Old 06-02-2021, 08:38 AM   #14
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Default Re: Fuel pump installation suggestions

My thoughts, it sounds like you wired your fuel pump to the ignition side of the coil and are getting an interruption of power to the fuel pump every time the points open.

You may need to rewire your ignition switch circuit so the switch is before the ignition coil, not after as in a stock Model A. This way you will have a "clean" 6v to the fuel pump (or relay).

Hope that makes sense...

Last edited by Y-Blockhead; 06-02-2021 at 03:41 PM.
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Old 06-02-2021, 08:16 PM   #15
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Default Re: Fuel pump installation suggestions

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Originally Posted by JayJay View Post
John - rebuilding one was a standard lesson in high school auto shop (anyone else remember high school auto shop?).

JayJay
Hey, High School was mid '60's, I lived about 35 minutes from Haight-Ashbury in San Francisco...What was the question again?
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Old 06-02-2021, 08:19 PM   #16
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Default Re: Fuel pump installation suggestions

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Originally Posted by Y-Blockhead View Post
My thoughts, it sounds like you wired your fuel pump to the ignition side of the coil and are getting an interruption of power to the fuel pump every time the points open.

You may need to rewire your ignition switch circuit so the switch is before the ignition coil, not after as in a stock Model A. This way you will have a "clean" 6v to the fuel pump (or relay).

Hope that makes sense...
You may have hit it on the head!... i will have to check it out tomorrow. The ignition switch had a wire going to the condenser and a wire going to I believe one of the terminals in the junction box on the firewall. I will have to verify this though.
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