Fuel Lift Pump

Lift Pump:

DESCRIPTION
The electric fuel lift pump mounts on the inside of the left frame rail, and is used to deliver fuel at a low pressure (at least 3 psi or 21 kPa) at the rate of 0.24 liter (1/2 pint) in 15 seconds (15 GPH). The lift pump is controlled by the lift pump electrical circuit.

Lift Pump Electrical Circuit
When the ignition switch is in the crank position, the fuel pump relay is energized which sends voltage to the lift pump. During this time, oil pressure is building to the point of closing the contacts of the oil pressure switch. A minimum of 28 kPa (4 psi) is required to close the switch contacts.

When the ignition switch is returned to the "run" position, the oil pressure of the running engine maintains voltage to the lift pump. If engine oil pressure drops below 28 kPa (4 psi), the engine will run poorly or stall when the lift pump circuit opens.