Need to know where to purchase a fuel pump?

There are two pumps one is the primary transferer pump while the other is the main pressure pump on the engine here is the feed pump you need from Rock Auto.

https://www.rockauto.com/en/catalog/volkswagen,1981,rabbit+pickup,1.6l+l4+diesel,1367737,fuel+&+air,fuel+pump,6256

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

Looks like I may be seeing the same issue you are having. I am finding an inline pump but not one in the tank. Here is a link to one common site that has them:

https://www.rockauto.com/en/catalog/volkswagen,1981,rabbit,1.6l+l4+diesel,1285062,fuel+&+air,fuel+pump,6256

Worst case scenario I would start contacting salvage yards and find out if they have any vehicles with this fuel system that may contain an operating part.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Unfortunately, on these older vehicles we are held to what we can find out of donor vehicles if we don't have a current supplier.

Hopefully this helps. Thanks