Monday, December 19, 2005
One of the problems you can face while converting a car from a carb to fuel injection is what to do about the gas tank. On a car designed for EFI, if the engineers have done their job right, the fuel tank will have baffles to prevent the fuel from sloshing around on corners. If you are working with a fuel tank not meant for EFI, the fuel can run to one side while taking a hard corner, and the pickup will be sucking air. Not good. So, if you don't have these baffles, and plan to do any hard cornering with your fuel injected car, you will need to find a way to prevent air bubbles from reaching your fuel rail.
There are three ways to deal with this. If you are lucky, you'll be able to bolt in a fuel tank from an injected version of your car. Or, you can modify your fuel tank to add baffles or a sump so as to prevent fuel slosh. The last option is a bit of a complicated one: Use a low pressure pump to transfer fuel out of your main fuel tank to a smaller surge tank. This surge tank separates out bubbles and has a deep sump that can feed into a high pressure tank.
Well, I can't weld very well, wouldn't want to weld a gas tank anyway, and there are no factory fuel injection tanks out there for A-bodies. Plus, I already have a low pressure electric fuel pump. So I decided to build a surge tank. Big thanks to Lamrith, who showed me how to use a fuel filter as a surge tank. My version has just a few twists added when it comes to flow control. As they say, if it's worth doing, it's worth overdoing.
I started with a Goldenrod industrial fuel filter from Tractor Supply. I then tapped the center of the spin-on mount for a 3/8" pipe that reaches to the bottom of the filter. At the top, I drilled a hole in the inlet side so that air bubbles can escape out the top and unneeded fuel can flow through the return. This return hole leads to a tee where it joins the return from the fuel pressure regulator and goes back to the gas tank. Many installations use fuel filters to restrict flow to prevent the low pressure pump from sending gas up the return line; I've substituted a one way check valve. I've also put a needle valve in the return to ensure enough fuel pressure to push fuel through the filter - I may wind up moving the needle valve from the return outlet to in between the top of the fuel filter and the tee, particularly if it creates a spike in fuel pressure. We'll have to see how this works out.
Now, I will have to find a way to mount this vertically and above the fuel pump.
Labels: Dodge Dart
What's the difference if the low pressure pump could or would pump some fuel up the return line, The high pressure pump would instantly overcome the low pressure and fuel will flow to th main tank. If the check valve was being held shut by the low pressure pump the same thing would happen, the high pressure pump return would overcome the low pressure and fuel would flow back to the main tank.
The needle valve is not necessary for fuel to flow through the filter. As long as you have about 1 ti 2 psi pressure difference across the filter, fuel will flow. It makes no sense to put UNNECESSARY restrictions in the fuel system, especially on the return line.
Squido says, "when in doubt, leave it out".
As you have it all the usable fuel will be filtered. Any unfiltered return from the low pressure pump will/can be mixed with the high pressure return to the main tank. The high pressure return is also free to return to the surge tank if needed, and be filter again.
I would put a coarse filter in the surge tank and add a fine filter after the high pressure pump.
I can think of many situations where that would be bad.
"do we need parachutes?"
doctor during operation "i dont remember taking this out"
Do I need condoms?