This post is pretty much a cross post from my other thread "Another AEM Infinity ECU Install on a Coyote" and I'll cover my fuel tank specifics here and not hi-jack my other thread.
I have been on the quest to convert my fueling system over to a FlexFuel setup so I can run either gasoline or E-85 on my fuel injected Coyote motor. I have pretty much upgraded most of the fuel system including, lines, filter, injectors, pump, ethanol sensor, etc. Engines will generally consume 30% more E-85 than gasoline due to the difference in fuel Stoich. Thus, being more thirsty it pushes and returns more fuel than typical for gasoline and the fueling systems needs to be able to handle this.
I took the roadster out last weekend and had all kinds of fueling problems leaving me on the side of the road 4 or 5 different times. At first, I thought it was the injectors since I had just swapped them out. With any amount of load on the engine it would start to die and stall. Even on the freeway. After limping back home later that morning, I began to pour through the data logs. The engine was going way lean. Upon further review, the injector pressure was dropping causing the lean condition caused by oscillations in the fuel pressure, and in some cases dropping to about 6 psi. It should be running at 55 psi.
After all the troubleshooting this is what I found. With the larger fuel pump (320 lph) in preparation for E-85, and the modifications to the return line on the in-tank pump hanger ports (I brazed in a 3/8" return line with an open dump instead of the stock 1/4" with the flapper valve), the problem had to be somehow related to this change. Theory 1 - no flapper/check valve at the end of the return line to create a little back pressure on the return line and the increased size from 1/4" to 3/8" was causing a loss in pressure (didn't seem reasonable but grasping at straws at this point). Theory 2 - I had met up with David Borden that morning and he provided this theory - the larger pump and lack of flapper/check valve may be creating a bunch of turbulence. Possible cavitation.
When running the pump with the engine off you can hear the fuel just really pouring back into the tank. Very likely aerated turbulence was causing the issue. I then swapped out the hanger for the original 1/4" return with flapper and the problem went away. In pulling the pump I had noticed that the fuel level was just shy of about 1/4 full. So I decided to pull the old hanger and replace it with the new modified hanger with the 3/8" open dump return and filled the tank up further. Turbulence went away and had solid fuel pressure. So, my unscientific conclusion is that when the tank falls below 1/4 the fuel return creates too much turbulence around the pump inlet port causing it to suck up air with the fuel. This would also explain why it was working fine earlier before the injector swap - it had more fuel in the tank. I either go back to the puny return and/or smaller fuel pump (neither of which I want to do), keep the tank above 1/4 full at all times or figure out a way to get this new setup to work.
I am using the Factory Five "complete kit" supplied Mustang fuel tank. And I'd say the baffling is nowhere near satisfactory especially when the tank is less than 1/4 full. This coupled with me running E-85 and being the tank is steel (not stainless) it will be prone to rust. I would probably need to treat it with some sealer.
I am going to upgrade the tank to deal with this issue. Here's the solution - Dave Boyd (Boyd Welding)!
I spoke to Dave Boyd about building me a tank as he has an EFI tank option for the Factory Five Roadster. However, I wanted some specific modifications to his tank.
Objectives: better baffling, sump, more resistive to high ethanol content fuel, larger fuel capacity.
Dave is going to make the tank to accept the new Aeromotive Phantom Flex pump assembly that I want to go with. In addition to Dave building the new tank with good baffling, this Aeromotive universal drop in unit comes with its own baffling/sump system that should further improve the situation. This tank is estimated to carry 22 gallons, doesn't drop down any further the the factory tank and mounts without the use of the tank straps. It bolts to the two vertical 3/4" tubes in the front and the horizontal 3/4" tube in the rear.
More info on the Phantom Flex system:
https://aeromotiveinc.com/phantom/
The only downside is that Dave only makes aluminum tanks. I would prefer stainless since I'm running high concentrations of ethanol in my fuel and that can be corrosive to aluminum. I may have the tank hard anodized inside but since I plan on running gasoline as well as E-85 and don't expect to keep E-85 in the tank for long periods, I think the aluminum will be fine.
Trevor
I have been on the quest to convert my fueling system over to a FlexFuel setup so I can run either gasoline or E-85 on my fuel injected Coyote motor. I have pretty much upgraded most of the fuel system including, lines, filter, injectors, pump, ethanol sensor, etc. Engines will generally consume 30% more E-85 than gasoline due to the difference in fuel Stoich. Thus, being more thirsty it pushes and returns more fuel than typical for gasoline and the fueling systems needs to be able to handle this.
I took the roadster out last weekend and had all kinds of fueling problems leaving me on the side of the road 4 or 5 different times. At first, I thought it was the injectors since I had just swapped them out. With any amount of load on the engine it would start to die and stall. Even on the freeway. After limping back home later that morning, I began to pour through the data logs. The engine was going way lean. Upon further review, the injector pressure was dropping causing the lean condition caused by oscillations in the fuel pressure, and in some cases dropping to about 6 psi. It should be running at 55 psi.
After all the troubleshooting this is what I found. With the larger fuel pump (320 lph) in preparation for E-85, and the modifications to the return line on the in-tank pump hanger ports (I brazed in a 3/8" return line with an open dump instead of the stock 1/4" with the flapper valve), the problem had to be somehow related to this change. Theory 1 - no flapper/check valve at the end of the return line to create a little back pressure on the return line and the increased size from 1/4" to 3/8" was causing a loss in pressure (didn't seem reasonable but grasping at straws at this point). Theory 2 - I had met up with David Borden that morning and he provided this theory - the larger pump and lack of flapper/check valve may be creating a bunch of turbulence. Possible cavitation.
When running the pump with the engine off you can hear the fuel just really pouring back into the tank. Very likely aerated turbulence was causing the issue. I then swapped out the hanger for the original 1/4" return with flapper and the problem went away. In pulling the pump I had noticed that the fuel level was just shy of about 1/4 full. So I decided to pull the old hanger and replace it with the new modified hanger with the 3/8" open dump return and filled the tank up further. Turbulence went away and had solid fuel pressure. So, my unscientific conclusion is that when the tank falls below 1/4 the fuel return creates too much turbulence around the pump inlet port causing it to suck up air with the fuel. This would also explain why it was working fine earlier before the injector swap - it had more fuel in the tank. I either go back to the puny return and/or smaller fuel pump (neither of which I want to do), keep the tank above 1/4 full at all times or figure out a way to get this new setup to work.
I am using the Factory Five "complete kit" supplied Mustang fuel tank. And I'd say the baffling is nowhere near satisfactory especially when the tank is less than 1/4 full. This coupled with me running E-85 and being the tank is steel (not stainless) it will be prone to rust. I would probably need to treat it with some sealer.
I am going to upgrade the tank to deal with this issue. Here's the solution - Dave Boyd (Boyd Welding)!
I spoke to Dave Boyd about building me a tank as he has an EFI tank option for the Factory Five Roadster. However, I wanted some specific modifications to his tank.
Objectives: better baffling, sump, more resistive to high ethanol content fuel, larger fuel capacity.
Dave is going to make the tank to accept the new Aeromotive Phantom Flex pump assembly that I want to go with. In addition to Dave building the new tank with good baffling, this Aeromotive universal drop in unit comes with its own baffling/sump system that should further improve the situation. This tank is estimated to carry 22 gallons, doesn't drop down any further the the factory tank and mounts without the use of the tank straps. It bolts to the two vertical 3/4" tubes in the front and the horizontal 3/4" tube in the rear.
More info on the Phantom Flex system:
https://aeromotiveinc.com/phantom/
The only downside is that Dave only makes aluminum tanks. I would prefer stainless since I'm running high concentrations of ethanol in my fuel and that can be corrosive to aluminum. I may have the tank hard anodized inside but since I plan on running gasoline as well as E-85 and don't expect to keep E-85 in the tank for long periods, I think the aluminum will be fine.
Trevor