Fuel Filter Construction

[Rearanger]

I've wondered why the fuel filter has three ports and how they worked. So I cut my old one open to get a look inside - but I still don't know completely how it works - maybe someone can help.

See the pictures:

This is how it looks from the outside


This is it pulled apart



Here's how the ports align



The two center ports connect directly. The fuel inlet port (larger on left outside edge) connects to the center outlet port (on right) through the filter media then out to the fuel rail - I'm assuming.

So what is the left center inlet port for? It looks like a return line to tank.

 

[txgocartB3000]

Standard configuration of a self regulating filter.

Excess fuel is returned to tank.

Ray

 

[ianyboy]

x2 alongside txgocart, think Ford adopted that return filter in 01. My pal has a 97, and it don't got the return

 

[Rearanger]

Excess fuel is returned to tank.

Then how is pressure maintained? I can see daylight through the center ports.

 

[MPRanger]

Then how is pressure maintained? I can see daylight through the center ports.

Fuel pressure is maintained with the fuel pressure regulator via the fuel pump. There is a "check valve" that blocks off the return line inside the tank while the engine is running. That's how it was explained to me anyway.


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[Rearanger]

I have been reading my FSM, as confusing as it is. It lists three possible systems - Returnable Fuel, Mechanical Returnless, and Electronic Returnless.

Knowing your system matters.

I believe what I have is a mechanical returnless. The electronic returnless use a fuel pressure sensor to vary the voltage to the pump to control pressure.

On the mechanical returnless the fuel pressure regulator is located in the fuel pump (not on the fuel rail) and there is a pulse dampener on the fuel rail (not to be confused as the pressure regulator). That means that the extra filter port, on the same side as the fuel inlet, is the return line to the pressure regulator. So this return line would see system pressure.

 

[MPRanger]

^^ That makes sense.


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