Fuel Control Valves

[SSTibet]

I need to understand some more about the fuel control valves.

1. I notice the gizmo on the fuel feed line, which is called the "schrader valve", and it looks like a small black knob from the outside. What is the function of this valve??? First time I hear a valve type like this? What is a "schrader valve" in general terms???

2. I also see the "fule pressure regulator" which is (a) connected to intake manifold vacuum and (b) is located on the fuel return line. How does the regulator function with the manifold vacuum?

Cheers all Corvette Lovers

 

[c4cruiser]

The Schrader Valve on the fuel line is pretty much the same as the valve in the tire stem where you check air pressure.

The valves purpose is really for releasing fuel pressure in the system when a technician has to work on any of those components. This vale is also where a furel pressure gauge can be connected to test the pressure in the system.

The C4 fuel system is under failrly high pressure at around 40-45 pounds per sq. inch. Carburetor systems will run between 4-15 psi depending on the fuel volume requirements. Some other fuel injection systems may have pressures somewhere in between. Most all fuel injection systems have a valve like this to release pressure during servicing.

The pressure regulator uses vacuum to operate. A drop in intake vacuum which is typically caused by opening the throttle body blades as you accelerate, results in lower vacuum pressure to the valve which then opens allowing more fuel into the system. More fuel flow results in lower fuel pressure between the valve and injectors and the regulator will then allow more fuel flow and resultant pressure from the pump. The regulator is desinged to limit pressure over a sepcified range to insure that excess pressure won't occur at the injectors.

 

[SSTibet]

C4cruiser,

Thx much for the information. But I thought the fuel pressure regulator is on the fuel retun line. Therefore when more vacuum applied to this valve, increased fuel flow will go to the tank rather than to the injectors... Am I confused?

Thanks again.

 

[Ken]

It's on the return, sorta...

The regulator is found at the end of the fuel delivery rails in order to both regulate pressure and maintain that pressure on the fuel system at the injector. If it was located before the injectors you would not get the full pressure to all of the injectors.

 

[G Winter]

Am I correct in saying the fuel pressure regulator is a bypass valve? If so the the way it opperates is to release fuel pressure when it gets to high?

 

[Ken]

Yeah, I guess you could call it that.

 

[WhalePirot]

The pressure is set with zero vacuum applied, similar to full throttle. At idle, the car needs less fuel; has max vacuum, so fuel is 'bypassed' back to the tank.


Great thread! Nice explain on the Shraeder valve.

 

[SSTibet]

WhalePirot,

Thx for your compliments for the thread. I am a true believer of understanding the basics before moving on to bigger & better stuff... That's why I started this thread and got good answers. Now it is time to find a cross section of the fuel pressure regulator to understand what's inside this gizmo... You have a picture like that?

Cheers all