6mm/8mm/10mm/12mm Hand Fuel Pump Line Rubber Aluminum Hand Primer Bulb Diesel Oil Transfer Petrol for Car Boat Marine Outboard

Description

Made of rubber and aluminum material, durable, oil proof and aging resistance. For introducing fuel into the fuel pump after replacement of the fuel filter. Connects to most length of hose. One-way only function. For transfer petrol, diesel, oil, water etc. Simple and effective tool for priming diesel engines on cars, motorcycles and boats. Frequently used as a hand pump in boats for fuel supply to the out-board engine. Specification: Material: Rubber + Aluminum Alloy Color: Black Input connectors: 6mm,8mm,10mm,12mm Length (overall): 15cm

FAQ:

Unable to let gasoline flow freely, but instead blocked it and prevented gasoline from passing through... stuck and unable to work.

---The check might be stuck. Please tap the metal ends of the hand primer pump or flush it with oil or water.

Troubleshooting & Reasons for Failure of Fuel Primer Bulb Pump

(6/8/10/12mm, for automotive & marine gasoline / diesel hand fuel pump with check valve)

1. Bulb springs back quickly after squeezing, cannot harden, fails to draw fuel (most common issue)

Damaged internal check valves (root cause)The two inlet & outlet one-way check valves may get stuck by fuel impurities or gum deposits; rubber valve seats may deform or lose sealing performance due to aging. The pump cannot build negative pressure, fuel cannot be sucked in and flows back once released. The bulb will never stay firm.

Air leakage on fuel line or fittingsLoose connection between barbed metal fittings and fuel hose, cracked aging hose, or improperly tightened hose clamps. Continuous air intake prevents vacuum formation and fuel suction.

⚠️ Note for selection: The inner diameter of the hose must match the pump size (6mm pump for 6mm hose, 12mm pump for 12mm hose). Mismatched pipe size easily causes air leakage.

Reversed installation directionThere is a flow direction arrow on the pump body. The arrow must point toward the engine. If installed backwards, the check valves will lock completely and stop pumping fuel. This is a frequent installation mistake.

2. Bulb cannot be squeezed, excessive resistance when pressing

Blocked fuel circuitThe tank strainer, fuel hose or fittings are clogged by fuel gum, rust or debris. Long-stale deteriorated fuel creates sludge and blocks the pipeline, resulting in no travel when squeezing.

Clogged tank vent holeBlocked vent on fuel tank cap creates negative pressure inside the tank, so fuel cannot flow out and the primer bulb struggles to draw oil.

3. The bulb can be pressurized and harden, but no fuel supply to engine; engine fails to start

The pump itself works, yet downstream fuel line / filter is clogged and fuel cannot reach the engine.

Poor fuel quality. Deteriorated fuel after long standing forms gum and blocks the pipeline on engine side.

Fuel level is too low; the suction inlet is exposed above fuel surface and draws air continuously.

4. Cracked bulb, fuel seepage or leakage

Aged rubber bulb: Long-term exposure to gasoline or diesel, UV radiation will make rubber brittle or swollen, forming cracks and causing leakage when squeezed. Gasoline is more corrosive to rubber, so service life is shorter than in diesel applications.

Physical damage caused by sharp bending or compression of the bulb during installation.

5. Other operational problems

Wrong mounting position: Install the primer bulb between fuel tank and engine. Keep the bulb lower than the fuel level in the tank. Vertical mounting delivers best performance. If placed too high, insufficient siphon vacuum leads to poor pumping performance.

Wrong size selection: Mismatch between pump port size (6/8/10/12mm) and fuel hose causes seal failure.

Low temperature environment: Rubber stiffens under cold conditions, elasticity decreases and pumping efficiency drops.

Quick Self-Check Sequence

Confirm flow arrow on pump body: Arrow points to engine, reverse installation is forbidden.

Verify hose inner diameter matches pump fitting size. Tighten hose clamps; check for cracks and air leaks.

Check fuel level. Ensure suction end is submerged in fuel and tank cap vent is unobstructed.

Squeeze repeatedly for test: A working pump will keep the bulb hard after pressing and hold pressure without fast rebound.

If bulb springs back rapidly after release = damaged check valve, primer bulb pump needs replacement.

Check pipeline for flattening, sharp bends or blockages.

Safety Warning

Gasoline is highly volatile. Keep away from open flame during maintenance to avoid fire hazard.

Stop use immediately if rubber bulb swells or cracks to prevent fuel leakage.