Test Description

Test Number 1)  Pressure, but less than 9 psi falls into two areas:

• Regulated pressure but less than 9 psi - Amount of fuel to injector OK but pressure is too low. System will be lean running and may set Code 44. Also, hard starting cold and poor overall performance.
• Restricted flow causing pressure drop - Normally, a vehicle with a fuel pressure of less than 9 psi at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine could surge and stop when pressure is too low.

Test Number 2)  Restricting the outlet side of the gage allows the pump to develop its maximum pressure (dead head pressure). With battery voltage applied to the pump test terminal, fuel pressure should rise to 13-15 psi as the pressure gage outlet hose is gradually pinched.

Test Number 3)  This test determines if high fuel pressure is due to a restricted fuel return line or a throttle body pressure regulator problem.