37 115C fuel system woes

Posted by tsherry On 2022/6/11 17:04:10

Need some advice here.

Third year into ownership of my 115C, much of which has been spent undoing previous owner's nonsense and rebuilding stuff that should've been done decades ago.

Over the winter, I replaced the non-stock fuel tank with a correct original, and had a new tank sending unit /pickup tube fabricated. All fuel hoses were replaced. Non-stock tank was out of some 1980's car, with four lines coming out of what was probably an electric fuel pump setup for a 12v. One was used for fuel, two crimped off, one for a vent hose.

Recently the car stalled on the way home from a short trip. Restarted, but felt like it was starving for fuel. Seemed like the fuel pump had given up, so I rebuilt it. Diaphragms were worn but no obvious holes.

Today was a larger test drive. Made it to the destination and then it died again on the way home, same symptoms. Got it off the road with help from other drivers, installed a 6v pump that I'd prepared as a just-in-case.

Got it restarted, made it a few more miles and it died again.

I'm wondering if the fuel cap is sealing so tight that the pump is not able to overcome the vacuum in the tank, and if I should add a vent to the filler line.

Advice anyone?