Measure the fuel inlet restriction. Install a vacuum gauge, Part No. ST-434, between the fuel pump inlet and the
gear pump inlet.
NOTE: Do not measure fuel inlet restriction with the fuel measuring device installed. This will not measure the inlet
restriction of the vehicle’s supply plumbing.
Hold the gauge at the same level as the gear pump.
NOTE: The gauge will not measure the correct vacuum if the gauge is not held at the same level as the gear pump.