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Discussion Starter · #1 · (Edited)
Eleminate fuel return line?

Im in the process of installing 5.0 Mustang EFI into my 68 Ranchero, and it's time to run the fuel lines. Im using a low pressure, external pump mounted close to the tank. That feeds an accumulator tank, which feeds a high pressure pump by the engine. lm using the stock 5.0 rail, so I have a return line.

My question is can I just run the return line from the rail into the accumulator tank, or do I need to run it all the way back to the tank?

Thanks
 

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The pressure from the low pressure pump to the accumulator is say 7 psi, so if the accumulator is full the return from the engine would need to be, say 10 psi, to get into it. If the pressure was that high then it would keep pushing back toward the tank and overwhelm the low pressure pump. Seems like it would be better to go back via a separate line.
 

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Re: Eleminate fuel return line?

Im in the process of installing 5.0 Mustang EFI into my 68 Ranchero, and it's time to run the fuel lines. Im using a low pressure, external pump mounted close to the tank. That feeds an accumulator tank, which feeds a high pressure pump by the engine. lm using the stock 5.0 rail, so I have a return line.

My question is can I just run the return line from the rail into the accumulator tank, or do I need to run it all the way back to the tank?

Thanks
Yes and NO You will have to run a line all the way to the tank. Or add a return line from the accumulator tank back to the tank, you cannot pressurize the return line even with 7 to 10 psi I would run it to the acc. tank then to the main tank from the acc. tank. You will also need to vent the tank the return will pressurize the tank.
 

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Discussion Starter · #4 ·
Thanks for the info. Looks like I'll be running a return line from the acc tank to the gas tank.


Sent from my Autoguide iPhone app
 

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Yep, every PSI on the return line directly adds to the pressure your rail is seeing. That throws off all your tuning and also tends to aerate your fuel significantly.
 

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+1. The circuit mus be complete to circulate cool fuel and to give the collected air bubbles a place to go. Return line to the surge tank (completes the high-pressure loop), and then on to the main tank (completes low-pressure loop). By comparison, "returnless" systems are only missing the rail return, and can do that as they have no air by then, and also run much higher fuel pressure to avoid vapor lock.

David
 
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