First time EFI fuel line prime question

[rjrobin2002]

I am getting ready to start my EFI conversion and have ran all of my fuel lines and pump. Today I put gas in my tank and directly ran my fuel pump with a 12V jumper pack. I disconnected the fuel line and have gas flowing to the fuel rail, but I have my return line by the tank disconnected to flush the lines out and no fuel is returning to the tank.
Should fuel pass through the rail and return without the engine running or does the regulator keep fuel from passing without a vacuum pulling on it?
I have a fuel pressure gauge hooked to the rail and am not getting any pressure either.

 

[rjrobin2002]

I also guess I should ask which of the lines on an Explorer fuel rail is the feed and return.

 

[brianstrange]

I also guess I should ask which of the lines on an Explorer fuel rail is the feed and return.

The smaller I.D. connection on the rail, is the return line. How is your system designed. Do you have an in tank pump?

 

[browngr5]

The return fuel regulator won't open if you just cycle the power to the fuel pump. Start the engine to provide vacuum to the regulator.

 

[rjrobin2002]

I have an external e2000 pump that is moving fuel fine. I just do not have pressure to my gauge or return fuel. I thought the pump should prime the fuel rail without the engine running so there would be pressure for the initial start up. That is why the pump is suppose to run 2-3 seconds when you turn your car on.

 

[rjrobin2002]

So the regulator is positioned after the fuel pump has pressurized the rail and vacuum controls fuel return to the tank?

 

[70_Steve]

You should have pressure on the gauge. I have basically the same setup, with the e2000 external pump, but I'm using the truck fuel rail. The vacuum line on the regulator only trims the rail pressure proportional to the manifold vacuum. Without vacuum on the regulator you should have 39 psi at the rail and the regulator should function, passing excess fuel down the return line.

 

[Broncobowsher]

With the pump running, you should have fuel returning to the tank.
You do NOT need vacuum for the return to work, sorry browngr5, you are wrong about that. That is not how the vacuum works on the regulator. Vacuum only adjusts the point it opens to maintain a constant pressure differental across the injector, counteracting the manifold vacuum pulling extra fuel through the injector.

It is VERY common to reverse the supply and return lines. I can't count the number of times I have encountered this during an EFI swap. Fuel pump goes straight to the fuel rails, regulator goes to the return line. It must be that way. Since you have no pressure in the rails, this is likly the cause. The pump is deadheading against the regulator. If anything is getting past the regulator it has an open and unrestricted path back to the tank.

 

[rjrobin2002]

I reversed the lines and it has return flow to the tank now.

 

[broncoitis]

That is correct about the lines! Ask me how I know? I had them reversed and was about to pull my hair out and then I thought maybe the lines are reversed? Ta Dah!!!

If you have it backwards you won't get any fuel pressure reading. You are basically pushing the fuel through the rail backwards and pushing the regulator shut with the fuel is how I thought about it.

Just remember that the 3/8 is the input and the 5/16 is the return and you should be good to go!

 

[browngr5]

With the pump running, you should have fuel returning to the tank.
You do NOT need vacuum for the return to work, sorry browngr5, you are wrong about that. That is not how the vacuum works on the regulator. Vacuum only adjusts the point it opens to maintain a constant pressure differental across the injector, counteracting the manifold vacuum pulling extra fuel through the injector.

It is VERY common to reverse the supply and return lines. I can't count the number of times I have encountered this during an EFI swap. Fuel pump goes straight to the fuel rails, regulator goes to the return line. It must be that way. Since you have no pressure in the rails, this is likly the cause. The pump is deadheading against the regulator. If anything is getting past the regulator it has an open and unrestricted path back to the tank.

Broncobowsher, Sorry to make the mistake. I assumed "electric relay" cycles pump off after 2 sec. not long enough for fuel to travel past closed fuel relay and come back to rear tank.Thanks for calling me out.

 

[POOH BEAR]

Are you running the factory tank?

 

[rjrobin2002]

I am running a 24 gallon Aero tank.