Fuel Pressure: Testing and Inspection

INSPECTION
- Make certain that there is fuel in the tank.
- Check for leaks at all fuel connections from the fuel tank to the carburetor.
- The engine should be running.
- Tighten any loose connections.
- Check all hoses for flattening or kinks that would restrict the flow of fuel.
- Check for air leaks or restrictions on the suction side of the fuel pump. Leaks on the suction side will seriously affect pump output.

FUEL PUMP FLOW TEST
- Remove the fuel supply line from the carburetor and insert it into a suitable container.
- Crank the engine.
- The fuel pump should supply 237 ml (0.5 pints) or more in 15 seconds.
- If the flow is insufficient, check for a restriction.
- If there are no restrictions, check fuel pump vacuum and/or pressure.

FUEL PUMP PRESSURE TEST
- Disconnect the fuel inlet line at the carburetor.
- Install a low pressure gage to the line.
- Start the engine.
- Fuel pressure should be 27.5 to 44.8 kPa (4 to 6.5 psi).
- If the pressure is low, check for restrictions in the fuel tank sender unit filter, lines and hoses.

CAUTION: Hold the carburetor fuel inlet nut while tightening the fuel line fitting to prevent carburetor damage.

- Connect the fuel inlet to the carburetor.

FUEL PUMP VACUUM TEST
- Disconnect the inlet hose at the fuel pump and connect a vacuum gage.
- Crank or run the engine until the maximum vacuum is reached.
- If the vacuum is less than 50.6 kPa (15 inches Hg), replace the fuel pump.
- If the vacuum is 50.6 kPa (15 inches Hg), check the fuel lines and hoses for leaks, kinks, or splits by disconnecting each section of line and connecting a vacuum gage. Crank or run the engine until the maximum vacuum is reached. The vacuum should be at least 50.6 kPa (15 inches Hg).