1 hour ago, Zed Head said:

Corrosion/rust.

But I thought the inside is stainless steel/aluminum, no? If there's corrosion/rust but its running fine now, should I replace it? The pump is only a couple of years old. This is the one I got: https://www.amazon.com/dp/B00496VHGC

Leave it alone and keep keep an eye on the pre & post filters IMO.

I believe fuel will crystallize. I have a 56 beetle that was left with fuel in it. The bottom of the tank was full of ruby colored amber. Took a chisel to get it out...

Didn't mean to contradict you directly. There might have been something in the fuel that was left behind as a solid. Crystalline and solid are two separate things in the materials world. A solid can be crystalline but it doesn't have to be.

Who knows, it might have been residual fuel stabilizer, left behind when the gasoline evaporated. Most of them are a witch's brew of chemicals designed to save the metals and the fuel.

I took some chemistry courses! 🤢

https://www.lucasoil.com/pdf/SDS_Lucas-Fuel-Stabilizer.pdf

https://defender.com/assets/pdf/sta-bil/safety_data_sheet_302110.pdf