Fuel Pump The First Stop on a No Start

When the machine will not start, check the fuel first, and a broken fuel supply usually lives at this pump. The 49040-7008 fuel pump does exactly that job.

What does it do on the engine? Fuel leaves the tank, passes through this pump, and the pump delivers it to the carburetor. On two-stroke small engines such as mowers, much of the fuel supply relies on the pump rather than gravity. When the pump stops, the carburetor starves, and the machine either will not fire or runs with a choke once it does. So on a no-fuel diagnosis, the first stop is the pump.

What is the screen on the pump for? Inside the inlet tube there is a brass mesh screen, and fuel passes through it before entering the pump. The screen holds back grit, water and old fuel sludge from the tank. When the screen clogs, the pump works hard but cannot pull, and the symptom looks just like a dead pump. That is why you blow the screen first and swap the pump only when the screen is clear.

Why is the shell metal with a seal ring? The body is metal, standing up to fuel and pressure, and a soft seal ring sits in the flange, the pump butting up to the carburetor seat so the circuit does not weep. The two mounting ears, one hole each, line up with the seat studs and are tightened diagonally.

When to replace it whole? If fuel still does not come after the screen is clear, if the body seeps, if the seal has hardened, if the flange is cracked, or if the pump has changed its sound and the pull is clearly weak, swap the whole pump. The diaphragm and spring inside are not sold on their own, the pump is one unit.

What to check when swapping it? Line up the mounting holes, and the count and direction of the ports, on the new pump against the old one. Engines in the same series mostly fit, but fit is not guaranteed for every one, so comparing against the old part is the safe way. After fitting, pull the fuel a few times by hand and check the flow before you start.