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Thanks to anyone offering help with my question, first. I have an '04 Z06 (shares the same fuel system as the C6) and first posted this in the C5 tech section with no response. I guess it's not as fun as arguing over which oil is appropriate. haha.
So I have replaced my left and right side fuel pumps during a clutch change project. I got everything back together and figured I would check to make sure everything works as designed before moving on to putting the drivetrain back in the car. So I fill the tanks to full with gas cans, removed the shrader valve from the fuel rail, put a jumper between 87 and 30 on the fuel relay, and began draining the tanks. Both sending units seem to be fine and the fuel gauge read full.
When I put power back to the car, the fuel pump started and all seemed fine, until the fuel gauge got to exactly half tank. I found the left tank drained, but did not siphon the right tank at all. I had a bitch of a time getting the fuel lines routed and attached to the left fuel pump, so I assumed I had kinked a line or something. Today I pulled both tanks out of the car and removed the fuel pumps to make sure everything was kosher. I put the fuel system back together and put about 13 gallons in. I attached my Te ch2 to the car and found the voltage on the right side was 1.57v, and did not move while pumping gas out of the fuel rail. The left side continually lowered from 2.49v to below 1v when I stopped. So I can assumed the left side is not siphoning fuel from the right tank.
So my question is, when I jump 87 to 30 at the relay, is there a reason the right side tank would not get reference voltage and not siphon? I have yet to check the pin at the pump and am struggling to find a pinout diagram that makes sense and explains what I should look for.
After reading some more last night, I am also wondering if draining the fuel from the fuel rail with an open line, thereby with only a few pounds of existing fuel pressure, would not be nearly enough fuel pressure to allow the right tank to siphon fuel to the left. I am hoping this is the case. I am also glad I went through the exercise of removing both tanks and the crossover a second time to make sure it is installed properly.
Can you rent or borrow a fuel pressure gauge? Is the fuel dribbling out or shooting out? If you have full pressure at the schrader valve than you know the lines in the crossover tube are connected properly and the system is sealed. If you do not have fuel pressure than there is an air leak somewhere. That's where I am at currently, everything looks finalized but I have no pressure at the line so think the crossover didn't seat properly. I'm not sure yours is the same issue but thought I'd add my $.02 of reference since I'm going through my issue at the moment. A couple other notes: My understanding is that the fuel pump in the left tank provides fuel to both the rail and the right tank because of a Y in the feed. The right side is a jet pump that provides fuel back to the left tank. So I would think the problem is there.
Can you rent or borrow a fuel pressure gauge? Is the fuel dribbling out or shooting out? If you have full pressure at the schrader valve than you know the lines in the crossover tube are connected properly and the system is sealed. If you do not have fuel pressure than there is an air leak somewhere. That's where I am at currently, everything looks finalized but I have no pressure at the line so think the crossover didn't seat properly. I'm not sure yours is the same issue but thought I'd add my $.02 of reference since I'm going through my issue at the moment. A couple other notes: My understanding is that the fuel pump in the left tank provides fuel to both the rail and the right tank because of a Y in the feed. The right side is a jet pump that provides fuel back to the left tank. So I would think the problem is there.
I own a fuel pressure gauge and have 58 psi at the rail, so I am now assuming it simply won't siphon without the schrader valve taken out and no pressure building up.
I'm hoping someone can give some input on that fact at this point.
Sucks to hear you are chasing a leak. I would order new hoses for the inside of the tanks and a new crossover to do it all in one swoop. It's such an anything system to work on with here cars.
If you did not restrict the fuel at the schrader valve, it will not draw fuel out of the right side tank. In other words, if you removed the schrader valve from the fuel rail and attached a hose to drain fuel, the right tank will not drain. I use a CA1 that I get from uri.com along with a 4 foot -4 hose http://www.uri.com/is-bin/INTERSHOP....8AAAFp1KIS3MSd
If you did not restrict the fuel at the schrader valve, it will not draw fuel out of the right side tank. In other words, if you removed the schrader valve from the fuel rail and attached a hose to drain fuel, the right tank will not drain. I use a CA1 that I get from uri.com along with a 4 foot -4 hose http://www.uri.com/is-bin/INTERSHOP....8AAAFp1KIS3MSd
Perfect. That's exactly what I was hoping to confirm. You're the man!
Here is what I pieces together out of hoses I already had on hand to drain the fuel. Worked fine with no leaks.
Thanks for the input fellas! Indeed it was just ignorance on how the system works on my part. I can say I'm infinitely more familiar with the fuel system now!
Happy to say I have dropping voltage in the right fuel level sensor and holding steady on the left, so I'm confident it's transferring at this point!
I'll be slumming it in the C5 arena shall you all need anything. Haha
Last edited by CinciZ06; Dec 31, 2019 at 06:57 AM.
Fuel pump help
