I have been replacing 38 yr old fuel lines and now have an annoying problem.

I can now hear my fuel pump whine fairly loudly when the engine is started. Like you can hear it over the idle of the engine.

What happened: I pulled the stinky supply line from the gas tank to the fuel pump. It appeared to me that the fuel pump inlet was a 1/2'', since my 5/16 line would not fit it and a 1/2 inch would. So I assumed it to be 1/2. Was this old line 2 sizes originally?

Got some fuel rated 1/2 line from the Truck supply house since AZ and OR didn't carry that large of lines in stock.

Put it on and now I hear the whine . Could this be from a larger fuel line capacity?

Or a coincidence since I touched the fuel pump(you touch it, you buy it!) is now going bad?

I have put some hose insulation since the new hose was pressing up on the floorboard. And this hose it DOT Truck rated line with metal mesh inside the rubber... Very stout stuff.

Car starts and runs the same, no leaks too!

Thanks.

On my '77 it's 3/8" coming out of the tank to the pump, or something metric that's close to 3/8's. From the pump foward it's 5/16". Here's something to read and then do. Z Car Tech Tips Fram G3 Filter Installation

10mm = approx. 3/8 intake

8mm = approx. 5/16 going forward.

The noise might be from your having damaged/bent/misaligned the fuel pump's rubber bushing system, so that you have metal-to-metal contact. Just a guess.

I will check out the mounting and rubber insulation next.

Here is a pic of the ?original line? You can see where the large end looks like it was molded that way, not just simply stretched around the fuel pump intake.