LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Porsche >> 1985 >> 944 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> DME System >> Testing >> Fuel Pressure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Fuel Pressure

  1. Locate fuel pipe cap nut at end of fuel rail. Remove cap being careful that sealing ball does not fall out. Connect a test pressure gauge (P 378 ).
  2. Start engine and maintain idle speed. Pressure gauge should show 29.4 psi (2.06 kg/cm2 ). Disconnect vacuum line at pressure regulator. Pressure gauge should show 33.8-39.7 psi (2.37-2.78 kg/cm2 ).
  3. Pinch fuel return line of pressure regulator. Pressure gauge should show a minimum of 59.0 psi (4.13 kg/cm2 ). If fuel pump does not meet specifications, check fuel filter or replace fuel pump and retest.
  4. If engine will not start, check fuse No. 2. If okay, remove fuel pump relay "U" and bridge terminals No. 30 and 87b. Pressure gauge should show 33.8-39.7 psi (2.37-2.78 kg/cm2 ).