Last try before I bring the car to a mechanic: fuel delivery problem

[E46m3zcp]

Okay, and there's another piece of info I'm missing. Does the line that links the left side to the right side (through which the venturi effect makes gas go) run inside the tank? (I'm trying to rule out misconnected hoses during reinstallation. It would not be fun to have to drop that tank again...).

To consider:
the car ran fine for 5-10 minutes, meaning at least the most crucial lines were connected adequately.

Another thing I was thinking is if the venturi line connecting both sides runs inside the tank, might I have messed/crunched up something by tightening the top nut of the tank (the one in the center of the car)?

The other theory is that everything is correctly connected (my buddy helped me remove the tank and we were too quick on this, I didn't take pictures and had to figure the plumbing out upon reassembly), but my fuel pump is failing, and not pumping enough volume for the jet pump to work adequately.

[eacmen]

Okay, and there's another piece of info I'm missing. Does the line that links the left side to the right side (through which the venturi effect makes gas go) run inside the tank? (I'm trying to rule out misconnected hoses during reinstallation. It would not be fun to have to drop that tank again...).

To consider:
the car ran fine for 5-10 minutes, meaning at least the most crucial lines were connected adequately.

Another thing I was thinking is if the venturi line connecting both sides runs inside the tank, might I have messed/crunched up something by tightening the top nut of the tank (the one in the center of the car)?

The other theory is that everything is correctly connected (my buddy helped me remove the tank and we were too quick on this, I didn't take pictures and had to figure the plumbing out upon reassembly), but my fuel pump is failing, and not p

I haven't ever had to repair this so I cant speak from experience but I believe that the sucking jet pump is inside the tank. This thread might be helpful: https://www.e46fanatics.com/threads/.../post-10088115

[Slideways]

How low is the fuel on the cluster and did it run for 5 min before or after you added fuel?

The siphon jet pump is inside the tank and can become disconnected if the small plastic tab on the drivers side level sender breaks off from fatigue. The fuel then won't be sent to the passenger side where the fuel pump is located. If fuel is added from a jerry can, it should go to the passengers side of the tank right where the pump is and the car should run until the fuel is emptied on that side.

[sapote]

If I understand it correctly - when the main fuel pump pumps fuel from the right side some of it gets consumed by the engine and the fuel rail but most of it gets pumped back to the tank on the left side via a fuel return line from the fuel rail. So Without the sucking jet pump the fuel pump will effectively just run the right side dry even if the engine isnt using that much fuel.

All of the returning fuel is dumped to the Right tank and part of the returning fuel is used to operate the jet pump to suck up fuel from the left and dump to the right.

"What then transfers gas from right to left? That's the part I'm missing. Is there a motor that does that?"
No fuel is moved from right to left; only when filling up the right to full, then addition fuel will flow to the left.

"I don't explain yet how the gas I put in there made it to the left side. The car didn't run long enough for the right to go dry by just consuming gas... So something drew the gas out of the right side of the tank, and into the left side of the tank. Is there an electric pump that does this, and a venturi-powered system that does the opposite?"

How much fuel you filled up the last time and how much the gauge shown the remain fuel? If not more than the right tank capacity, then there should be no additional fuel added to the left tank, unless there was fuel in there before filling up, or a part of the return line broke in the left tank and dump fuel in there.

[E46m3zcp]

Responding the questions asked above:

- A full large jerry can was added to an empty tank
- This made the tank gauge in the instrument cluster point to above 1/4 (no low fuel light)
- The gas was added BEFORE trying to start the car (be advised that the pump ran dry now because of this issue and the gas being all to the left).
- The gauge still shows approximately this.

From what I understand from the previous few answers,
- No mechanism transfers gas from passenger (right) side to driver (left) side - except when filling up.
- Gas is sucked from left to right by some passive device which uses the return line flow and the Venturi effect
- The return line dumps returning fuel in the passenger (right) tank while providing suctioning to transfer gas from driver (left) to passenger (right).

I filled with a jerry can and this fills up the right tank. There was absolutely no gas in the tank on either side prior to that (the tank was removed and all of the contents dumped to a jerry can and burnt in another car)

I’m trying to wrap my mind around how the contents of my jerry can made its way to the driver (left) side tank

I will double check all of the connections this evening to make sure I didn’t do anything dumb like plugging the return line into the driver (left) lobe. What could really help here is a photo of the plumbing on top of the tank (how lines should be connected)

[sapote]

“I’m trying to wrap my mind around how the contents of my jerry can made its way to the driver (left) side tank
”
Then the return line got loose in the left tank and dumped most of the fuel in there

[E46m3zcp]

Thanks for all the help so far. Does anyone have an image or a diagram showing what hose plugs where on top of the gas tank? Something like the following, but with some identification:


If not, I am mostly curious about the left side (driver side) of the tank. There are 2 connections there, a blue one to the left, and another one on the fuel sender cover. What is the purpose of each of them?
I'm mainly wondering if that would be possible that I screwed up and connected the return line to the wrong of the 2 possible places on the left side. This would explain that fuel is being dumped on the left side and not sucking fuel from left to right.

The way I now understand this is that the return line must be connected on the left side but the returning fuel goes to the right side through a jet pump hose that connects both sides internally (inside the tank). The movement of gas from left to right in this device is what creates the suction to transfer gas from left to right. If the return line was connected to the wrong location, then the jet pump is not doing anything. The returning fuel is flowing into the left side of the tank and there is no suction to transfer any gas.

The way I currently have it connected is: the leftmost connection in the image is connected to the return, and the one on the left sender / cover is coming from the right side (probably something going to the evaporation charcoal canister - I'm guessing). I'm starting to think it's likely that I screwed up.

[simonnim]

Is it easy to connect the wrong line? When I did subframe and dropped it. It seemed pretty straightforward on how it connects.

[E46m3zcp]

Thanks. This makes me 95% sure I messed up.

If someone can confirm that
1 is the charcoal canister (black line going towards the right)
2 is the return line (blue line going to filter)

This will confirm I have inverted them.

[E46m3zcp]

For anyone looking for this information in the future:
"2" in my previous post is where the return line goes (the one that runs on the left side of the car to the pressure regulator).

It is possible to mistakenly connect the line that should be in "1" there as it is the same size... The consequences are:

• You are no longer providing the siphon pump with any flow/volume. The pump is no longer working.
• "1" goes directly into the left side of the tank, so if your return is connected there it's dumping all the fuel there.

Expect the car to die at 1/4 tank and all the fuel to be on the left side. You'll hear the pump buzzing, will see your 12.75V at the pump, and will measure a current that makes sense. If you purge gas lines using a purge valve on a pressure gauge, you'll see a lot of air in there. That's because the tank is empty where the pump is.

Follow the procedure posted above to measure the amount of fuel in each side.

[eacmen]

For anyone looking for this information in the future:
"2" in my previous post is where the return line goes (the one that runs on the left side of the car to the pressure regulator).

It is possible to mistakenly connect the line that should be in "1" there as it is the same size... The consequences are:

• You are no longer providing the siphon pump with any flow/volume. The pump is no longer working.
• "1" goes directly into the left side of the tank, so if your return is connected there it's dumping all the fuel there.

Expect the car to die at 1/4 tank and all the fuel to be on the left side. You'll hear the pump buzzing, will see your 12.75V at the pump, and will measure a current that makes sense. If you purge gas lines using a purge valve on a pressure gauge, you'll see a lot of air in there. That's because the tank is empty where the pump is.

Follow the procedure posted above to measure the amount of fuel in each side.

So you're all squared away?

[E46m3zcp]

So you're all squared away?

After fixing the connections (which I double-checked were wrong) and adding some gas, the car is running normally and the pressure is back where it should be. Unless I damaged the pump from running it dry a couple of times (which time will tell) I am otherwise okay. Thanks for your help!! I was on the edge of giving up and bringing the car to a mechanic and now it's running smoothly. The lesson I learned is always document how things are before undoing them

[simonnim]

This is the clearer image of the return.


It's always a good idea to take pictures. In my case I only got a few hours here any there to do the subframe. So I forgot what was going on by the time I got back to it and used images as a reminder of what I needed to go or what step I was on.