During my E30 325iX rehabbing, I found that the return line into the fuel tank was plugged. I replaced the tank, but had not until now investigated the blockage.
I took the old tank to the band saw where my dad works.
Here is the return line inside the tank:
You can see that the return line comes in the side of the tank, the goes down to the bottom of the tank, then back up and over the driveshaft hump, emptying into the swirl chamber in the right lobe. The changes in the diameter of the tube are a venturi/jet pump that uses the velocity of the return fuel flow through the return line to suck fuel from the left lobe of the tank... which then flows out at the swirl chamber so that fuel doesn't get stuck in the left lobe.
Here's the line following removal from the tank:
Here's a closeup of the jet pump:
The blockage is *likely* where the small diameter inlet tube meets the profiled larger diameter outer tube at the joint on the right side of the photo, but I haven't dissected the pump any further yet at this point to determine for sure.
I took the old tank to the band saw where my dad works.
Here is the return line inside the tank:
You can see that the return line comes in the side of the tank, the goes down to the bottom of the tank, then back up and over the driveshaft hump, emptying into the swirl chamber in the right lobe. The changes in the diameter of the tube are a venturi/jet pump that uses the velocity of the return fuel flow through the return line to suck fuel from the left lobe of the tank... which then flows out at the swirl chamber so that fuel doesn't get stuck in the left lobe.
Here's the line following removal from the tank:
Here's a closeup of the jet pump:
The blockage is *likely* where the small diameter inlet tube meets the profiled larger diameter outer tube at the joint on the right side of the photo, but I haven't dissected the pump any further yet at this point to determine for sure.
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