Chart A-4A Fuel System Diagnosis

Chart A-4A:

DFI Fuel Pump Circuit:

DESCRIPTION:

The DFI system requires that fuel pressure be 9.0-12.0 PSI and steady under all driving conditions. The J25400-300 or equivalent (0-60 PSI) pressure gauge may not show small variations in fuel pressure. For a more precise and more responsive gauge reading, use the 0-15 PSI gauge head (from the essential tool gauge number J29658/BT8205) attached to the hose with schrader valve fitting from the essential tool gauge J34730-1 or equivalent.

NOTES ON FAULT TREE:

1. Fuel pressure should be 9.0-12.0 PSI and steady. If the fuel pressure is not in this range, go to CHART A-4B to diagnose fuel pressure out of range.

2. If the pressure drops off (leaks down) at key off, either the fuel pressure regulator cannot hold pressure or the fuel pump check ball is not seating. This branch of the trouble tree will determine which is causing the pressure leak down.