LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 1988 >> Seville Base >> Repair and Diagnosis >> Engine Performance >> System >> DFI ECM Tests W/Codes >> Chart A4A - Fuel System Diagnosis
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Chart A4A - Fuel System Diagnosis

The DFI system requires that fuel pressure be 9-12 psi and steady under all driving conditions. Fuel Pressure Gauge (J-29658/BT8205) should be attached to fuel line service fitting with a Schrader valve fitting from Gauge Set (J-34730-1). This set up will give the technician a more precise and more responsive reading.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Fuel pressure should be 9-12 psi and steady. If not, go to CHART A4B - FUEL PRESSURE OUT OF RANGE.
  2. If fuel pressure drops (leaks down) with key off, either the fuel pressure regulator cannot hold pressure or the fuel pump check ball is not seating. This branch of trouble tree will determine which is causing the fuel pressure leakdown.
Fig 1: Flow Chart A4A Schematic, Fuel System Diagnosis
G57237
Fig 2: Flow Chart A4A, Fuel System Diagnosis
G57238
Fig 3: Flow Chart A4A, Fuel System Diagnosis
GB0048483