System Diagnosis - Fuel System Pressure Test - Carbureted Models

Fuel Pump Flow Test:
1. Connect hose from carburetor fuel feed line to a suitable unbreakable container and crank engine.
2. Fuel pump should supply 1/2 pint or more in 15 seconds.
3. If flow is below minimum, check for fuel restriction. If there is no restriction, check pump pressure and/or vacuum.

Fuel Pump Pressure Test:
1. Disconnect the fuel line at the carburetor.
2. Install a low pressure gage onto the line.
3. Start the engine.
4. Fuel pump pressure should be 4 to 6.5 psi.
5. If pressure is less, check for restrictions in fuel tank sender filter, lines or hoses.
6. Reconnect the fuel line.

Fuel Pump Vacuum Test:
1. Disconnect inlet hose at fuel pump and connect a vacuum gauge.
2. Crank or run engine until maximum vacuum is reached. If the vacuum reading is less than (15" Hg.), replace the fuel pump. If more than (15"Hg.), go to step 3.
3. Check fuel lines and hoses for splits, leaks or kinks by disconnecting each section of line and connecting a vacuum gauge. Crank or run engine until vacuum reaches it's peak. Vacuum should be at least 15" Hg. If less, repair or replace the malfunctioning line or hose.
4. If the fuel lines and pump check OK, remove tank unit, replace strainer and clean the tank.