We have not found a solution to a main fuel pump noise that sounds like cavitation or sucking air. The fuel rail sees 40 pounds with dips in pressure and slight stumble in engine rpm when the sound occurs.

All the following: main fuel pump, fuel filter, tank fuel pump, tank fuel pump sock, tank hose, fuel pressure regulator, fuel pump relay, and fuel pump fuses -were replaced and substituted with the noise still there.

There is no fuel leak under the car or around the tank. The sender assembly is properly installed in the baffle with a 3/4 full tank. The noise continues for a second or two after the key is turned to off. We have verified the pumps are running and even used a small battery to run the main pump with the noise still present. We did not have a set of fittings to measure the tank pump output pressure while the engine is running.

Will some new tank pumps, 1) run slower than the old one, 2)run slow enough with voltage above 9V (SAE Spec Limit low) not to keep up with the main pump, or what? Next task will be get fittings to check pressure, wires, and output of tank pump unless someone has another suggestion to offer.