How to Check for Suction on a Vacuum Fuel Line

Proper pressure is required in fuel lines so that the fuel maintains proper compression and travels appropriately through the line. Proper pressure creates a vacuum that pulls the fuel through the line at the proper rate. Leaks disrupt the process and are sometimes challenging to detect. Checking for suction in a vacuum fuel line helps ensure that the system works properly and that leaks are not a danger.

Screwdriver
Vacuum gauge

Instructions

- 1
  Disconnect the suction line by either gently pulling the line off at its end with pliers or by unfastening a clamp that holds it in place. It depends on the specific engine and some clamps require a screwdriver to remove while others come off manually. If the line has a cam-lock connector, it comes off with a push and a twist. Top off the fuel tank with fuel. Plug a vacuum gauge into the inlet port. The end of the gauge should slide or twist right into the port opening.
- 2
  Turn on the motor and loosen the bleed valve by turning it counter-clockwise with a screwdriver to allow some air into the system. Only turn it a quarter-turn at first and then open the valve more as needed.
- 3
  Read the gauge and close the bleed valve once the gauge reading reaches 15 inHg (inches of mercury).
- 4
  Turn off the system and watch the valve. If the line has proper suction, it should hold the vacuum reading on the gauge for 5 minutes.

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