How do I test a mechanical fuel pump off the vehicle?

Flush the pump in a fuel bath while operating the rocker arm, then drain the fuel. Block the inlet port and confirm the pump arm does not move; release the inlet and listen for a suction sound; block the outlet, build air pressure with the rocker arm, and confirm pressure holds for two or three seconds; finally, with pressure built up, submerse the pump in a fuel bath and check for air leaks.

How long should a good fuel pump hold pressure with the outlet blocked?

After building up air pressure with the outlet port blocked, the pressure should remain for two or three seconds.

What should happen when the inlet port is blocked?

With the inlet port blocked off, the pump arm should not move.

How is a fuel pump checked for air leaks?

Put a finger over the outlet port, build up pressure in the pump, then submerse the pump in a fuel bath and check for air leaks (bubbles).

What confirms the pump produces sufficient suction?

After blocking the inlet port, remove your finger and listen for a suction sound, which confirms sufficient suction was produced.

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Nissan Micra Mechanical Fuel Pump Inspection Procedure - EF & EC-10

Fuel pump inspection procedure with suction and air-leak test steps and figures

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Step-by-step fuel pump inspection procedure checking suction, pressure hold, and air leaks.

AI caption June 2005 · Photo 110 of 412

This service manual page describes the bench inspection procedure for a mechanical fuel pump. It is a single page (EF & EC-10) from the Engine Fuel & Emission Control section of a factory service manual. The procedure lists five steps: (1) flush the pump by immersing it in a fuel bath while operating the rocker arm several times; (2) drain fuel, block off the inlet port, and verify the pump arm does not move; (3) remove the finger from the inlet port and listen for a suction sound confirming adequate suction; (4) block the outlet port, operate the rocker arm to build air pressure, and confirm the pressure holds for two or three seconds; and (5) block the outlet port, build pressure again, and submerse the pump in a fuel bath to check for air leaks. Two line drawings (reference codes SEF881A and SEF867A) show a technician holding the pump and blocking ports by hand while working the rocker arm; one callout reads "Dose not move" (does not move). A reader learns how to verify a mechanical fuel pump's valve sealing, suction, and pressure-holding capability without special tools.

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Frequently asked questions

How do I test a mechanical fuel pump off the vehicle?: Flush the pump in a fuel bath while operating the rocker arm, then drain the fuel. Block the inlet port and confirm the pump arm does not move; release the inlet and listen for a suction sound; block the outlet, build air pressure with the rocker arm, and confirm pressure holds for two or three seconds; finally, with pressure built up, submerse the pump in a fuel bath and check for air leaks.
How long should a good fuel pump hold pressure with the outlet blocked?: After building up air pressure with the outlet port blocked, the pressure should remain for two or three seconds.
What should happen when the inlet port is blocked?: With the inlet port blocked off, the pump arm should not move.
How is a fuel pump checked for air leaks?: Put a finger over the outlet port, build up pressure in the pump, then submerse the pump in a fuel bath and check for air leaks (bubbles).
What confirms the pump produces sufficient suction?: After blocking the inlet port, remove your finger and listen for a suction sound, which confirms sufficient suction was produced.