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Old 08-11-2019, 06:55 PM
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Electric Fuel Pump Plumbing?

I am currently running a mechanical fuel pump on my 383 SBC. I am thinking about going to an electric fuel pump. It's probably a good idea to install a return line at the same time. That is where the problem is. My fuel tank has no fittings except for the rollover valve and the fuel outlet at the bottom of the tank. My question is: Could the return line be T'ed into the fuel line just below the tank and before the pump? I don't know if the head pressure of the tank would keep the return line from pushing bypassed fuel into the tank. Any body have any experience here?

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Old 08-11-2019, 07:51 PM
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I would think you would just end up pressurizing your return line, no ?

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Old 08-11-2019, 08:17 PM
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Quote:
Originally Posted by jaw22w View Post
I am currently running a mechanical fuel pump on my 383 SBC. I am thinking about going to an electric fuel pump. It's probably a good idea to install a return line at the same time. That is where the problem is. My fuel tank has no fittings except for the rollover valve and the fuel outlet at the bottom of the tank. My question is: Could the return line be T'ed into the fuel line just below the tank and before the pump? I don't know if the head pressure of the tank would keep the return line from pushing bypassed fuel into the tank. Any body have any experience here?

You can do that, it's not the best of form but it is ahead of self bypassing pumps that do it internally.


Self regulating pumps that use an internal bypass have no distance to allow the bypass fraction to cool after being pumped. This often leads to such pumps getting the return fuel hot enough to vaporize inside the pump which with rare exception stalls the pump. The biggest problem comes at slow speeds where most of the fuel (especially with high capacity pumps) is being bypassed.



If you place a bypass regulator in the engine compartment away from heat sources as practical then run the bypass return the distance back to the pump this does provide some time for the bypass fuel to cool before entering the pump again.


There is a third option of Pulse Width Modulated (PWM) pumps that control pressure by on to off time, this of course introduces electronic complication but eliminates the regulator and return.


Bogie
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Old 08-11-2019, 08:49 PM
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I guess we all have our favorite ways of plumbing the fuel system, so I'll chime in with mine. First of all, the return line should allow the excess fuel to just "fall" into the top of the main fuel tank. If you have to remove the tank to make a hole, then you have to remove the tank to make a hole.....get over it. The regulator can be installed either before or after the carburetor, but I prefer it after the carb and before the tank, as shown in figure 3 here......
https://documents.holley.com/199r11227.pdf
This installation will do the best job of keeping the fuel cool.

Plumb your fuel pressure gauge into the line between the carburetor and the bypass regulator. Begin at under 5 psi for an Edelbrock by turning the pressure adjustment screw counter-clockwise. The course filter before the pump will prevent jamming up the line and fraggin' the pump from overheating. The fine filter after the pump will catch fines that would jam up the carburetor. BULLETPROOF.

Mount the pump in rubber. Never bolt an electric fuel pump to anything metal on the car. The droning will make you nuts in short order. I used to use lengths of muffler-hanging rubber that had white fabric molded into it to help hold its shape. Bolt the rubber to the car and then bolt the pump to the rubber. Use a short piece (less than 2" long) of non-metallic line immediately before and immediately after the pump to isolate the supply lines from the steel of the car. I like to tie the line down with rubber-insulated Adel clamps about every 12 inches from the tank to the motor. If you are going to drag race your car, DO NOT run the fuel line(s) in the driveshaft tunnel, the Tech Inspector won't like it.

Here's a plethora of rubber products that could be used to mount an electric fuel pump. Use your imagination.
http://exhaustdirect.com/Brackets-and-Hangers/?page=5
.

Last edited by techinspector1; 08-11-2019 at 09:15 PM.
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Old 08-12-2019, 05:14 AM
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What is the vehicle and what is the arrangement of the fuel tank?

Is there a short rubber hose connecting your fuel filler/cap to the top of the tank? If there is, there may be space to install a pipe with a return fitting in that section of hose. Also, what does the tank use for a sending unit? Some sending units bolt into the top of the tank, and have space to drill an extra hole for a return fitting.

Bruce
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Old 08-12-2019, 11:17 AM
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Quote:
Originally Posted by 75gmck25 View Post
What is the vehicle and what is the arrangement of the fuel tank?



Is there a short rubber hose connecting your fuel filler/cap to the top of the tank? If there is, there may be space to install a pipe with a return fitting in that section of hose. Also, what does the tank use for a sending unit? Some sending units bolt into the top of the tank, and have space to drill an extra hole for a return fitting.



Bruce
+1, this is what I have done before.

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Old 08-12-2019, 11:25 AM
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https://www.summitracing.com/parts/v...SABEgI-WPD_BwE

This anywhere in the top of the tank will do just fine.
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Old 08-12-2019, 12:10 PM
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I had a Stewart-Warner 240A fuel pump on my 1955 Chevrolet, 1970 455 Pontiac engine with two Holley #4224 (660 CFM each) carburetors. The SW pump would run until the pressure built up in the single fuel line to the carburetors. Apparently that pump was a Pulse Width Modified type that Bogie referred to. It would only run until the system was pressurized and then quit pumping.

When I finished a WOT 1/4 mile run, the pump would run until the system was fully pressurized again. Apparently that fuel pump was internally regulated.

Shelby Cobras we’re equipped with a StewartWarner 240A electric fuel pump.

Last edited by MouseFink; 08-12-2019 at 12:17 PM.
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jaw22w (08-13-2019)
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Old 08-12-2019, 02:33 PM
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This is the tank and car in question. The car is literally built around the tank. I am talking MAJOR disassembly. It can be removed, but I would rather forget the idea of an electric pump than have to remove that tank. Hind sight says I should have added a couple of bungs when I built the tank. I had to build it to fit the available space. I never even considered an electric pump while building this car. And the thought of welding bungs on a used gas tank scares the hell out of me. I have been welding for more than fifty years and I have made a point of never welding on gas tanks unless new. Maybe one of the reasons I am still here.
As I am not going to disassemble half of the car to install a fuel pump, my only real option is to plumb the return line T'ed in. I think the pump pressure would over come the head pressure of the tank, I am worried that the pump might overheat if it has to work too hard to overcome the head pressure.
Edit: Whoops pics didn't come through. I'll try again.
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Old 08-12-2019, 02:37 PM
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Quote:
Originally Posted by johnsongrass1 View Post
https://www.summitracing.com/parts/v...SABEgI-WPD_BwE

This anywhere in the top of the tank will do just fine.
Yep! That will do it. Thanks!
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Old 08-12-2019, 02:55 PM
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I will try again
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Old 08-12-2019, 05:56 PM
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Quote:
Originally Posted by jaw22w View Post
As I am not going to disassemble half of the car to install a fuel pump, my only real option is to plumb the return line T'ed in. I think the pump pressure would over come the head pressure of the tank, I am worried that the pump might overheat if it has to work too hard to overcome the head pressure.



For a decent pump this isn't an issue as a performance pump will have plenty of excess capacity. My preference for street rods with carburetors is to use an external low pressure TBI pump which has an output in the range of 15 to 20 psi. Since a carb only needs 5 to 6 psi with a bypass regulator the pump has plenty of capacity to deal with the return on the bypass. In reality the entire system will see the bypass pressure setting. The volume in the bypass side will change with usage by the carb and the flow pressure and volume will also be adjusted by the regulator for changing fuel level in the tank,


Obviously the best setup is to return to the tank above the fuel level, but for a few inches of fuel height in the tank any bypass back pressure from the fuel level is nominal.


Bogie
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Old 08-14-2019, 07:43 PM
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Look at he first few pics in this album. It shows my recent evolution of electric pumps. There were several others before these. I have run all of these with no return. I live in the SoCal desert. Find the captions.

After the pumps there are switches to both provide a low oil pressure light and break power to the pump if the engine stops in a collision.

I have lately been putting 2 micron Racor filters before the pumps on everything. I recently managed to stuff one behind the left rear tire along with an inline fuel pump when I installed EFI. On EFI I put a 30 micron filter after the pump to catch busted pump parts.

https://goo.gl/photos/LJNV4esgmYmSzKdL8
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Old 10-11-2019, 09:24 AM
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In my opinion it all comes down to practicality. Does the car run alright with a mechanical pump? If so, problem solved, keep the mechanical pump.
If you believe it has to have an electric pump,bite the bullet and remove the tank and do it right.
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Old 10-11-2019, 02:28 PM
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I agree that you should determine whether you really need an electric pump but it looks to me that it would not be that difficult to drill a hole in the top of the tank near the sender unit and put an AN bulkhead fitting in place. Yes you would have to drain the tank but the opening for the sender unit would allow you stick a shop vacuum hose in the tank and collect any metal shavings that drop into the tank. A 90 degree connection and line to the pump would finish off the project.
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