So I was riding on the highway and the car died suddenly. I have a fuel pressure gauge on the fuel rail showing no fuel pressure. I heard no noise coming from the fuel pump. So I had it towed home and ordered a fuel pump. My fuel guage level readings were dropping to zero then going to a half a tank. When I would clear the code, the fuel reading was accurate so I assumed the fuel sending unit electronics were on their way out. I knew it could be something else but I figured the fuel pump was 20 years old. Might as well replace that. After dropping the Tank, I realized the driver side tank was bone dry, but I had filled up 30 minutes prior. The passenger side tank is 100% full. I know that the way the fuel system operates it’s supposed to run the passenger side out of fuel first so I’m not really sure where to start. I know the driver side fuel pump pressurizes the lines through the crossover tube to get the pump in the passenger side tank to send fuel back over, so I’m not sure why it would be full unless the pump in the passenger tank is bad or there was some kind of vapor lock or issue with a broken fuel line. I’m going to drop the passenger side tank today. Any advice on what to look for? Thank you guys.

 

.....and what were the codes?

 

I believe it was a P1431 fuel sensor code was the one I could reset to get the fuel gauge back to an accurate reading. That worked for a few weeks but then at some point it would only reset to half a tank, but it didn’t throw a code when it died it just ran out of fuel on the driver side.

 

I just hooked up the battery and put it on a charger and I’m seeing some historical codes for the bcm column lock but I install the lock elimination years ago that doesn’t cut fuel does it?

 

I should probably give you some more information on the vehicle. It has an A&a dual fuel pump kit with the return line and regulator by the fuel rail. The factory pump is on it BAP because it’s a supercharged vehicle.

 

So your profile says you have a 2004....but the P1431 is an older PCM DTC....if I recall correctly.
What is the history here? When is the last time the car ran without issue?

 

The car ran fine up until this issue. I deleted the code unfortunately to correct the fuel level without documenting it. I was going off an article I had saved after the issue which is why it wasn’t correct. The gauge issue began a few months ago after going over some rather large speed bumps I deleted the code and the gauge issue didn’t come back for a few weeks until 30 mins after going across a road with a bunch of pot holes was when the car died. Don’t know if this is related to the issue. If the proper code is essential for diagnosis I can reinstall the tank and crossover put some fuel in it and try to run the car to get the code to come back up. Sorry about the bad information.

 

I just plugged in the pump harness with the pump out of the driver side tank and cycled the key forward without starting. The pump runs for a few seconds so I’m getting voltage with the key forward so it’s not a fuse, relay or ground issue.

 

Ok. It did not make sense, which is why I asked. Codes are not required ...just helpful putting the story together. Good luck getting it solved.

 

Not familiar with the a&a dual fuel pump system. You will have to find out why the driver side tank ran dry while the passenger side was still full. On stock cars the fuel pump creates a siphon condition that pulls fuel from the passenger side fuel tank, there is no fuel pump in the passenger side fuel tank.

 

I just dropped the passenger tank and found the 6 of the 10 pins that contact the card were broke off. If this tank thinks it’s empty will it stop it from pumping over to the other tank with the pressure regulator? That’s the only wiring that goes into the unit to the regulator.the only other thing I can think of is maybe the evap selenoid is bad and it’s vapor locking it?

 

On a stock c5 the fuel level sending units only send a voltage level to the pcm which then sends a voltage to drive the gauge, there is no control function associated with fuel levels. There is a small orifice in the drivers side fuel tank that creates the siphon that draws fuel from the passenger side fuel tank.

 

Usual problem is that the jet pump in right tank is clogged and not pumping fuel to the left tank, but this is not consistent with left tank being bone dry so soon after refueling.

The right tank jet pump gets its motive flow from tubing running from the left tank electric pump discharge. I would be suspicious of a broken or disconnected motive flow line in the right tank resulting in the electric pump pumping fuel from left to right.

If the PCM senses improper amount of fuel between the tanks, it will drive the gauge to zero and throw a code. It is easy to mistake this for a sensor problem and run out of gas with fuel trapped in right tank. Ask me how I know.

 

So I think I had two separate problems occurring. The pins on the float arm that contact the level sensor card broke off going over the pot holes which was giving me the sensor code. Secondly the turbo smart vacuum controlled fuel pressure regulator provided with the A&A kit has a return system. I think that the secondary regulator was allowing the fuel pressure to hang below 54 psi at low rpm cruising. I believe it was running through the return line instead of pumping to the siphon pump on the passenger side. It seems to be enough of an issue with running a vacuum controlled regulator that racetronix and lingenfelter sell factory regulator block off plugs to deal with this exact issue. I will keep you guys posted if this corrects the issue when they arrive.