MitsuStyle - View Single Post - My 2005 CTS-V

**asshanson** · 09-24-2010

I finally figured out the fuel issue. I disconnected the fuel feed line and turned the pump on for 60 seconds, and I got 1/3 gallon of gas. I tried directly out of the tank and I got the same result, so nothing in the lines/filter is restricting flow. Then I took out the pump and tested the stocker, 255, and 310 pumps I had sitting around, direct hookup to the battery. The stock pump and 310 were each able to do about a gallon in 60 seconds, and the 255 was able to do more than a gallon in 50 seconds, so clearly the 255 pump is more than capable of providing the fuel required.

I put the pump back in the assembly and dropped it into my bucket of fuel to test that out, and I found where all the fuel is going: out some stupid valve I don't think should even exist.

You can see the red line connects to the pump and the mystery white plastic item. That valve thing also connects to the hose that goes outside the tank, the connection from the other pump on the opposite side of the tank (yes, there is an active pump that feeds fuel from the drivers side to the passenger side of the hump), and a plastic tube that plugs into a dead end. I really dont know what it's for. Anyway, about 2/3 of the fuel is spraying out that stupid plastic piece and not going out of the tank.

Anybody familiar enough with returnless or GM fuel systems to know what that thing is? I'm considering bypassing it and hooking the pump directly out of the tank, and having the other pump just feed the bucket the primary pump sits in. I think it's supposed to be some merger valve that combines fuel from the other pump along with the main pump, but I think it may have broken and it's just bleeding off most of the fuel.

EDIT: I added arrows to the flow. I think red arrows should be the expected flow of fuel, but the black arrows are the actual flow. I'm thinking a seal or something inside the siphon has broken.

09-24-2010	#100
asshanson immune from paybans Join Date: Oct 2005 Location: West Des Moines Drives: poorly Posts: 4,358	Re: My 2005 CTS-V I finally figured out the fuel issue. I disconnected the fuel feed line and turned the pump on for 60 seconds, and I got 1/3 gallon of gas. I tried directly out of the tank and I got the same result, so nothing in the lines/filter is restricting flow. Then I took out the pump and tested the stocker, 255, and 310 pumps I had sitting around, direct hookup to the battery. The stock pump and 310 were each able to do about a gallon in 60 seconds, and the 255 was able to do more than a gallon in 50 seconds, so clearly the 255 pump is more than capable of providing the fuel required. I put the pump back in the assembly and dropped it into my bucket of fuel to test that out, and I found where all the fuel is going: out some stupid valve I don't think should even exist. You can see the red line connects to the pump and the mystery white plastic item. That valve thing also connects to the hose that goes outside the tank, the connection from the other pump on the opposite side of the tank (yes, there is an active pump that feeds fuel from the drivers side to the passenger side of the hump), and a plastic tube that plugs into a dead end. I really dont know what it's for. Anyway, about 2/3 of the fuel is spraying out that stupid plastic piece and not going out of the tank. Anybody familiar enough with returnless or GM fuel systems to know what that thing is? I'm considering bypassing it and hooking the pump directly out of the tank, and having the other pump just feed the bucket the primary pump sits in. I think it's supposed to be some merger valve that combines fuel from the other pump along with the main pump, but I think it may have broken and it's just bleeding off most of the fuel. EDIT: I added arrows to the flow. I think red arrows should be the expected flow of fuel, but the black arrows are the actual flow. I'm thinking a seal or something inside the siphon has broken. Attached Thumbnails Last edited by asshanson; 09-24-2010 at 12:28 PM..