Can someone explain this factory fuel pump assembly?

[JOLENE_THE_RANGER]

2011 ranger 4cyl fuel pump.
im helping a friend put a fuel cell in his truck and he wants to use the factory fuel pump.
unfortunately i did not take this apart so im asking for some explanation of what ports do what up top of the unit.
i know which is which for the fuel lines, but theres two other fittings up top. one is about 3/8" and the other about 5/8. i believe the bigger one used to go to the charcoal canister?? wheres the other one go?
thanks

 

[bobbywalter]

Emmission line is fat bastard...pump line and vent line.

 

[bobbywalter]

Vent to oem filler neck....I can see where that may be confusing when I thought about it.

 

[JOLENE_THE_RANGER]

thats what i was thinking but wanted to be sure. we are getting rid of the emissions junk so ill be venting the regular vent line to the atmosphere with a one way ball valve and capping off the pump line.
thank you!

 

[Dirtman]

You can't use a one way valve on a vent line, the tank needs to breathe both in and out.

 

[sheep herder]

You can't use a one way valve on a vent line, the tank needs to breathe both in and out.

Hush! That's a secret.

 

[bobbywalter]

Do a loop and 1 psi.

 

[JOLENE_THE_RANGER]

You can't use a one way valve on a vent line, the tank needs to breathe both in and out.

youre right. i was tired this morning. shouldnt have said one way, its a ball valve that will only close if the trucks upside down.

 

[Dirtman]

Also thats a returnless style pump, but there IS a return on it... the regulator is internal so there's no return from the fuel rail itself BUT it's designed to use with a filter with a bypass valve that returns to the tank. So there is a fuel OUT and fuel RETURN. Whether you can just cap the return line I dunno.

 

[Uncle Gump]

So... it's a returnless return system. Yay!

 

[Dirtman]

So... it's a returnless return system. Yay!

Exactly!

Technically the fuel pump regulator has the return, the older systems the regulator is on the rail so fuel returns from the rail back to the tank. This pump has the regulator in the tank so the excess fuel just drains right back inside the tank.

I'm not 100% sure the purpose of the return style fuel filter. My working theory is that it works like an oil filter. If the filter clogs too much it bypasses it back to the tank in order to protect the pump?

I just know how the setup works... not why... maybe @adsm08 knows.

But there is 2 lines into the fuel filter, one out.

 

[RonD]

Yes it is a Return system as Dirtman said

This is a little better picture of the assembly: https://img.go-parts.com/catalog/wp/full/38AEED7.jpg

You can see the Pump OUT fuel line, from top of pump to top of assembly
Then you can see the Return line assembly down to FPR(round with silver center) then down to bottom of tank
FPR is set for 55-60psi

OUT is larger than Return

The fuel filter will have 3 ports: IN from pump, OUT to engine, Return to gas tank

Another picture here, same thing but different "look": https://ic.carid.com/spectra-premium/fuel-delivery/sp2133m_1.jpg

The filler Vent is usually not on the fuel pump assembly, it's either inside the filler pipe or a separate connection on the top of the tank
The EVAP is and does Vent when engine is off

 

[adsm08]

I just know how the setup works... not why... maybe @adsm08 knows.

Physics mostly. Also accountants.

The fuel is used to cool the pump. Fuel returning from the engine is hot. Fuel that doesn't make it to the engine is less hot.

That's the reason for a returnless fuel system. The reason for the mechanical returnless is that is was cheaper to build than the electronic returnless system.

The mechanical system just has a pressure bypass in the filter. The electronic one needs a pressure sensor, wiring, and often Ford used a seperate driver module, which all adds up to money.

 

[Dirtman]

 

[Dirtman]

Engines is goes vroom?