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Discussion Starter · #1 ·
I didnt pay attention in any science class so if one of you who did can answer this Id appreciate.

if you have a fuel pump thats mounted below the fuel level but above the sump is it still being gravity fed as long as the pump is below the fuel ?
 

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If you put a straw into a glass of water but not to the bottom, you can still "suck" the water up the straw. Most people assume that you are drawing in the water, but it's actually being pushed up the straw by 14.7 pounds (at sea level) per square inch of ambient air pressure.

Most mechanical pumps create "suction" or a low pressure like the straw example. Atmospheric pressure pushes the fuel into this low pressure.

Electric pumps are better at pushing fuel out than "sucking" it in, plus they need a steady supply of fuel to keep the pump cool. That's why you see in-tank electric pumps. Pump is kept primed and cool.
 

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low pressure area

the fule pump is creating a low pressure area on the inlet to the pump , pressure goes from high to low so the fluid will go toward the low pressure. Then once the pump is primed it should keep ok. The pump would do better with more " head pressure " by being located at the same height as the sump.
 

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Paul Wright said:
If you put a straw into a glass of water but not to the bottom, you can still "suck" the water up the straw. Most people assume that you are drawing in the water, but it's actually being pushed up the straw by 14.7 pounds (at sea level) per square inch of ambient air pressure.

Most mechanical pumps create "suction" or a low pressure like the straw example. Atmospheric pressure pushes the fuel into this low pressure.

Electric pumps are better at pushing fuel out than "sucking" it in, plus they need a steady supply of fuel to keep the pump cool. That's why you see in-tank electric pumps. Pump is kept primed and cool.
Yep, that's just what I was thinking.:D
 

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On my car when I ran the electric pump it was above the sump but below the fuel in the tank. The weight of the gas in the tank would push fuel out of the line going to the pump. It worked fine until the tank got really low on fuel then it would go dry. The pump inlet was 2-3 inches above the sump.
Getting the pump low enough to work right without putting a fuel cell in the trunk is one of the main reasons I went to a mechanical pump.
 

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Discussion Starter · #7 ·
the fule pump is creating a low pressure area on the inlet to the pump , pressure goes from high to low so the fluid will go toward the low pressure. Then once the pump is primed it should keep ok. The pump would do better with more " head pressure " by being located at the same height as the sump.
hey thanks. now I understand what PW was trying to say.
 

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Discussion Starter · #8 ·
On my car when I ran the electric pump it was above the sump but below the fuel in the tank. The weight of the gas in the tank would push fuel out of the line going to the pump. It worked fine until the tank got really low on fuel then it would go dry. The pump inlet was 2-3 inches above the sump.
Getting the pump low enough to work right without putting a fuel cell in the trunk is one of the main reasons I went to a mechanical pump.
thanks for the info. this is what I wanted to know
I think I will go ahead and do it (I want the pump in the trunk instead of under the car.)

how low did the fuel have to be in the cell for the line to go dry? 2-3 inches?
 

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If you put an electric pump in the trunk it will sound very loud. The trunk will act like an echo chamber. You'll want to mount the pump low enough to stay primed.
I think there are places that offer in tank fuel pump conversions. .
 

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Getting the pump below the sump is a pain. Specially if its a stock tank. But... I think even stock modern systems with the pump in the tank are above the bottom level quite a bit. Unless they are sitting at the bottom, without a pick up tube.

I have an electric pump and fuel injection. I wanted the head pressure to always be there for the pump. So I mounted my pump below the sump.

A lil easier for me cause my 20 gal. tank is a cell mounted high. But look at my pictures. That huge tank hanging down is mostly air, prolly 6 inches. I surrounded the aluminum tank with steel to protect it from road debris. The reason the steel case is so low is I have two large filters and the pump inside of it, to the right, all enclosed and lower than the fuel cell, I didnt want those pieces out in the open either. I could have made the tank case smaller and made a separate case for the fuel pump and filters but it would have looked uneven and the pump case would have been just as low as it is now. I wanted the piece of mind knowing the pump was always under fuel. First concern for me with this car is dependability and driveability (SP?). It might look better when the bumper is on, who knows. JR

This is without the bumper. But see how far it hangs down, and Im flat on the ground taking this pic so you wont always be seeing this.


I have had the bumper on and it hangs down a lil lower than the top slice of this pic, the bumper hides the frame rails.


Fuel cell in the trunk.
 

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This explains why my old pump could only draw about 10 or 11 gallons out of the tank. It was mounted on the frame rail at about mid level of the tank.
 

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Discussion Starter · #12 ·
If you put an electric pump in the trunk it will sound very loud. The trunk will act like an echo chamber.
I had not thought of this. thanks.

Im still gonna mount it in the trunk though. Im not comfortable having a 500 dollar pump and filter setup hanging in the air for all to see.

is there anything that can be done to cut down on the sound?
 

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Do you have a cell in the trunk? If so, why not just build a stand out of 1x1 steel tubing that you can get at the local hardware store adn mount the entire cell, sump and all, in the trunk. Then you'd have nothing hanging down outside the car, and wouldn't have to worry about this problem. I used a couple peices of 2" square tubing that I laid down on the trunk floor, then ran the bolts thru my cell straps, thru the tubing, and thru the trunk floor, bolting it all together and to the trunk floor at the same time. The only thing showing under the car was 4 bolt heads. Then I ran my fuel line out thru a body plug.
 

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Aeromotive has a new Stealth kit that mounts the pump inside the sump. You can remove the pump for service or change the 100 micron prefilter without draining the tank.

I think they even now have new Nova tanks with the sump and pump installed. A1000 pump supports over 1,000 hp and if that's not enough they have 2,000hp kits
 

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Im not comfortable having a 500 dollar pump and filter setup hanging in the air for all to see.

is there anything that can be done to cut down on the sound?
?????????? what's wrong if someone see's it? You would have to be looking for it, on your hands & knees, or driving behind you.

I rubber shock mount mine and it cuts down the noise a lot. I've done it on three cars now. They are still somewhat noisy but that's just the nature of the beast...I don't even notice it unless someone else asks what that noise is.
 

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What cha say mike???????can't hear ya, your damn pump is too loud! :d can't you hear that! Rm
 

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What cha say mike???????can't hear ya, your damn pump is too loud! :d can't you hear that! Rm
Haa!! Now thats funny. Why?? Cause hell, when my engine is running you dont hear the fuel pump. LOL All you hear (and feel) is engine, its not a Honda. Guess if I had a honda engine I would be thinking about fuel pump noise. But NOPE, the small block makes enough sound to drowned out any simple fuel pump noise.

If the loudest noise a guy hears in his ride is the fuel pump then the cam isn't large enough, plain and simple. JR
 

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Discussion Starter · #18 ·
Do you have a cell in the trunk? If so, why not just build a stand out of 1x1 steel tubing that you can get at the local hardware store adn mount the entire cell, sump and all, in the trunk. Then you'd have nothing hanging down outside the car, and wouldn't have to worry about this problem. I used a couple peices of 2" square tubing that I laid down on the trunk floor, then ran the bolts thru my cell straps, thru the tubing, and thru the trunk floor, bolting it all together and to the trunk floor at the same time. The only thing showing under the car was 4 bolt heads. Then I ran my fuel line out thru a body plug.
Ive thought about this, but I have a plastic cell and I heard that its not a good idea to not have it well supported.

do you think this would work to just have two pieces of 1x1 or 2x2 holding up the cell?
 
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