killernoodle

So I finally got my fuel system up and running and I'm running into an issue. Here is the system so far:
'05 CTS-V
Stock 3/8" feed line from the tank, through a regular filter with no built in regulator
Repurposed Evap 5/16" line for the return to the tank. Spliced into stock 5/16" line where the old filter/regulator were under the car.
Dual Bosch 044 in a surge tank where the airbox used to be. Only 1 pump is turned on at the moment.
Fuelab 525 regulator at the end of the fuel rails dumping back to the surge tank

Right now when I key the car on the stock pump primes and one of the 044s turns on and I can adjust the base pressure to 58lbs and it holds it just fine.

After starting the car, the pressure jumps to 70lbs and I can't adjust the pressure anymore with the regulator. It's like it has a mind of its own now. I'm starting to suspect a blockage in the return line to the stock tank but I'd like to get some feedback before I head out to the shop and start poking around in the dark.

Ollie8974

What brand surge tank did you use.
Can you post a photo of the surge tank.

killernoodle

Sorry about the garbage pics. The two -6 lines going to the back of the bay are the feed and return lines from the stock fuel tank and pump. The surge tank is something I made from this piece from integrated engineering and some 1/4" aluminum plate I had around. Both 044s are genuine. The way it's hooked up, the secondary fuel pump is hooked up to a hobbs switch and isn't activated until it sees boost. The secondary pump has a check valve before the Y, the primary does not. It's a -8 from the Y to the driver side rail, a -8 crossover, and the passenger rail terminates at the Fuelab 525 which returns a -6 to the surge tank.

Right now I don't have the regulator hooked up to the charge pipe for boost reference, it's open to atmosphere. Like I said, I can dial the fuel pressure with the car keyed on after priming, but as soon as I start it the pressure jumps to 70 lbs and no turning of the adjustment screw on the regulator changes the fuel pressure.

bumpnzx3

I think the return line is too small (the 5/16" line you're using). When there's a restriction in the return line, you will have a hard time getting the pressure down low enough. When the car is shut off, the pump is only seeing around 12v. When the car is running, the pump is probably seeing more voltage. More voltage on a brushed motor pump, means it's going to be pumping more.

Once you get the return line issue fixed, you may still have a hard time getting your pressure low enough when the second pump kicks on. The 525 inline regulator won't bypass as much fuel as the 515 series regulator. I don't know the exact flow of those two pumps combined, but it's something to keep in mind once you start using both pumps.

By design, a regulator really can't fail. About the only failure you will see is a bad diaphragm. When/if that happens, there's fuel coming out of the boost reference port. If your pressure is too high, either there's a restriction in the return line or the regulator is too small for the application. If the pressure is too low, it's a supply side problem. 99.9% of the time, the regulator is not the cause of pressure problems.

killernoodle

I figured out what the problem is:

Turns out the fuel system on the V isn't like the corvette where the regulator is in the fuel filter. The filter looks the exact same as that style and I just assumed that since there was a return line coming from it, the regulator must be in the filter.

Well it turns out the regulator is in the tank and I had to pull the bucket and yank the guts out of the regulator to get the fuel to return nicely. Everything works flawlessly now!