Fuel psi less than 50 psi = no start (GM CPI Vortec)

Описание: This video covers the basics of fuel pump pressure, current, power and ground testing that can be applied to ANY electric fuel pump. We also go into some unique properties of the GM CPI “poppet” style injection system, and where it differs from typical fuel injection systems.
Lower than normal fuel pressure is often misdiagnosed on the central port injection system. For example: Fuel psi at 49 psi during cranking will be a no start! Just about every other fuel injection system will start and run fine with this kind of pressure. But the GM CPI needs a minimum of 50 psi to open the mechanical injector poppet nozzles.
This design was used on the 4.3, 5.0 and 5.7 engines throughout the 90s.

Engine Performance Diagnostics chapter 16 pages 2 - 6, 9 - 16

Symptoms
intermittent no start condition
starts when a fuel source is used (carb. Clean, starting fluid etc) and may continue to run normally after it starts
possible hesitation/bog on acceleration once running depending on how weak the pump is
fuel system lean trouble codes (P0171, P0174)

Fix
fuel pump replacement

Tests shown
how to check fuel pressure on a GM CPI system
how to use a GM fuel pump test connector and fused jumper wire to energize a fuel pump
using a low amp probe and scope to check an electric fuel pump
how to check an electric fuel pump power and ground
understanding the impact of a plugged fuel filter on fuel pump current

Tools used
fuel pressure gauge
low amp probe
fused jumper wire
lab scope

Playlist
(Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing
   • (Chapters 14, 15,16) Fuel Delivery and Fue...  

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