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Volvo fuel pump puzzler

A recently podcast puzzler is about a fuel injected Volvo that won’t run well if the fuel level in the tank is below 1/2 full. This Volvo is configured with two fuel pumps, a low pressure feeder pump mounted in the tank, and a high pressure pump mounted between the tank and the fuel injection rail. I got to wondering why Volvo engineers would configure the fuel system that way? Seems unnecessarily complicated. Why not just put one high pressure pump in the tank as is done w/most modern vehicles, and completely eliminate the need for a feeder pump?

Here’s the puzzler link

https://www.cartalk.com/puzzler/pump-down-mileage

The puzzler is 30 years old, that was the common configuration in the 1970’s.

This puzzler sound like a tale, the vehicle owner was driving a car that was squirting gasoline from a leaky fuel line, enough to affect fuel economy but did not complain about the odor.