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**asshanson** · 02-25-2013

I know this isn't mitsu related, but fuel systems are pretty universal, just think of this as a fuel cell. Here is a pic of the fuel system on my car as it sits today:

Right now the tank has two AN bungs on the bottom left side of the tank, one for the feed line and one for the return.

My first question is, can you have the pump after the filter? Someone told me the filter should always be after the pump, something about not having too much restriction on the inlet of the pump.

Next, the main problem with this setup is the tank is internally divided into two sections, the right 1/3 of the tank is completely separate with a few check valves that allow fuel to flow into that side, but not back into the other side. So basically with this setup there is about 2-3 gallons on the side where the OEM sending unit is (nothing hooked up there), and I can never access that fuel because it's pulling from the other side.

I have a few options that I've been considering, but I don't know enough about fuel pumps and fluid dynamics to know if it will will introduce problems.

1st solution: add a fuel pump in the stock location and Y into the feed line after the other pump. The drawback is I think the right side of the tank might empty first sine the return is going to the left side. I know there are the valves that allow fuel to flow back into the right side, but they just work on gravity and I'm not sure they can support the amount of flow that the fuel pump is putting out. So basically the left side would fill up faster than it can drain to the right side, and the right side pump would be running dry and burn out or something. Plus if it's putting out air I'm not sure how that would affect fuel pressure at the point it runs dry, there might be a drop in pressure for a second. Does that make sense?

2nd solution: weld in a bung to the right side of the tank, and Y the line right before the filter, so that the existing pump would be pulling from both sides of the tank. Again my question is what happens when the right side is empty, and the pump pulls from a full line and an empty line simultaneously? Does air get introduced, or will it just pull the fuel from the full line?

Hope this makes sense, basically you have to think of it as two separate tanks since one side could go empty before the other. I can draw pics of solutions 1 and 2 if it will make more sense.

02-25-2013	#1
asshanson immune from paybans Join Date: Oct 2005 Location: West Des Moines Drives: poorly Posts: 4,358	Custom fuel setup question I know this isn't mitsu related, but fuel systems are pretty universal, just think of this as a fuel cell. Here is a pic of the fuel system on my car as it sits today: Right now the tank has two AN bungs on the bottom left side of the tank, one for the feed line and one for the return. My first question is, can you have the pump after the filter? Someone told me the filter should always be after the pump, something about not having too much restriction on the inlet of the pump. Next, the main problem with this setup is the tank is internally divided into two sections, the right 1/3 of the tank is completely separate with a few check valves that allow fuel to flow into that side, but not back into the other side. So basically with this setup there is about 2-3 gallons on the side where the OEM sending unit is (nothing hooked up there), and I can never access that fuel because it's pulling from the other side. I have a few options that I've been considering, but I don't know enough about fuel pumps and fluid dynamics to know if it will will introduce problems. 1st solution: add a fuel pump in the stock location and Y into the feed line after the other pump. The drawback is I think the right side of the tank might empty first sine the return is going to the left side. I know there are the valves that allow fuel to flow back into the right side, but they just work on gravity and I'm not sure they can support the amount of flow that the fuel pump is putting out. So basically the left side would fill up faster than it can drain to the right side, and the right side pump would be running dry and burn out or something. Plus if it's putting out air I'm not sure how that would affect fuel pressure at the point it runs dry, there might be a drop in pressure for a second. Does that make sense? 2nd solution: weld in a bung to the right side of the tank, and Y the line right before the filter, so that the existing pump would be pulling from both sides of the tank. Again my question is what happens when the right side is empty, and the pump pulls from a full line and an empty line simultaneously? Does air get introduced, or will it just pull the fuel from the full line? Hope this makes sense, basically you have to think of it as two separate tanks since one side could go empty before the other. I can draw pics of solutions 1 and 2 if it will make more sense.