While my wording (working from memory) may not have been exact, the service manual will tend to disagree with your thoughts on the check valve. While there is an anti-siphon hole there is also a reverse flow check valve in the left tank pump assembly....it is item 16 in the photo in eboggs link.

From the service manual:

 

The fuel is maintained fairly level in the two tanks during consumption. The fuel is fed from the left to the right on filling and taken from both on consumption. There are two sender assemblies, one in each tank.

 

You are correct that there is a check valve from the fuel pump and it does appear before be before the line to the jet pump. First, clearing the discussion - there are 2 pipes in the jet pump system. The one from the left to the right is the one showing the check valve inline and the one from the right to the left is the one with the hole to break the vacuum and prevent siphoning. Now, back the the pressure line from the left to the right, the idea that the check valve is between the fuel pump and this line seems incorrect since this would allow the pressure in the fuel rail to force fuel backward toward the fuel tank but then down the line to the venturi pump. The check valve would be effectively bypassed. I have to believe the line to the jet pump comes off BEFORE the check valve that maintains fuel in the line to the engine -OR- there is a second check valve in the secondary pressure regulator in the left tank which would cost more and be another part to fail. That leads me to believe either the diagram is incorrect or I have a great idea for a way GM can save some money unless there is already a check valve in the secondary pressure regulator in the right tank.

Actually there is probably no need for any anti-siphoning measures in this pressure pipe since it is a very small pipe compared to the low pressure return line which has the hole. This line DOES need to be isolated from the fuel rail to maintain pressure and fuel in the line to the engine but it isn't going to flow a lot of fuel at zero pressure.

Now I'm going to really disagree. Imagine if the jet pump were to pump a little less than the engine requires. The left tank would go dry while there was still fuel in the right pump. The dry sump around the fuel pump in the left tank would prevent fuel from being pumped to either the engine or the jet pump so the fuel in the right tank couldn't be used. Now imagine if the jet pump delivers a little more fuel than the engine requires. Now the left tank fills to overflowing while the right tank level drops. The fuel pump always has fuel as long as there is any fuel in either tank.

The design is for the jet pump to pump more fuel than the engine would normally need. This ensures that all the fuel in both tanks can be used. If the design was to keep an even level in both tanks then there would be no need for the anti-siphon hole. Instead of letting air into the line the design would be to pump fuel to a common line to ensure it was always full both tanks allowing both tanks to siphon to each other all the time.

Another issue that would come up with even levels is what would happen if you ran the tank near empty and then added just 7 gallons? When you fill the tank, very little fuel splashes up to the overflow pipe at the top of the left tank. It almost all goes initially into the left tank. Without the ability to siphon it across and with a jet pump trying to drain any remaining fuel in the right tank, how do you get it balanced again?

When the gauge reads half a tank the left sensor is reading full and the right sensor is reading empty and the computer knows that means 1/2 a tank. If anyone thinks otherwise, come on back. I've still got some more nails for the coffin.

 

Well, I have neither the inclination nor the ability to disagree with you. Of all of the systems on the Corvette, the fuel delivery is one area where know the very least.

What I posted was my understanding of the system from various conversations that I've been involved in and I just don't have the technical knowledge of the system nor information at my disposal to dispute your post. I'm not inclined to agree with you regarding the balancing of the tank for a couple of reasons, I just don't have the ability to back up my beliefs. I'll do a little more digging and see if I can't give you a little more sport next time around.

 

I'm pretty sure it has something to do with the "flux capacitor"

 

See the link I posted - http://www.hessh.de/Corvette/FuelTankSystem.pdf
I don't recall any question on the fuel system ever posted here that wasn't answered in depth on that link.

From a performance standpoint it is desirable to balance the weight between the tanks (a full tank has over 60 pounds of fuel) but from a design standpoint it is difficult without a pipe under the drive shaft.

 

thanks for the explanation! also now that the mystery of the 2 fuel sending units explained i understand. see i was trying to figure out how both tanks stayed at the same level, and now i see they don't!
a crossover tube at the bottom would have been my first guess. simple in design!

 

i wonder why the system has the RH tank empty first and keep the LH tank full. you'd think with the driver in the seat that it would want the fuel kept on the opposite side.

but fine with me, as my SC head unit and battery are over there.

 

One reason there is no crossover at the bottom of the tanks and under the drive shaft:



I totally agree. Maybe that is why GM hasn't hired us to design Corvettes.

 

The corner balance w/driver doesn't work like you'd think. Adding my 169#'s to my '05 Z51 M6 Coupe w/less than 1/4 tank added 51# to the LF 72# to the LR, 16# to the RF and 30# to the RR. Cross weights were 50.7% before drivers weight and still 50.7% after! Started out 54% Front, 46% Rear, added my weight and ended up w/53% Front and 47% Rear. Since the tanks are behind the driver, adding gas (to the right? tank) PROBABLY would balance F to R AND L to R even closer.

Strangely enough my '08 Z51 A6 was closer to perfect, 50.0% cross weight and 51% F and 49% R w /1/4 tank.