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Home >> Porsche >> 1989 >> 911 Turbo, 2D Convertible >> Repair and Diagnosis >> Engine Performance >> System >> Basic Testing >> Fuel System >> Fuel Pressure

Fuel Pressure

Basic diagnosis of fuel system should begin with determining fuel system pressure.

CAUTION: High fuel pressure may be present in fuel lines and component parts. Relieve pressure before attempting to open system for testing or component replacement. Do not allow fuel to flow onto engine or electrical parts or allow an open flame in area while testing fuel system components.
  1. Locate fuel pipe cap nut at end of fuel rail. Remove cap, being careful that sealing ball does not fall out. Connect Test Pressure Gauge (P 378).
  2. Start engine and maintain idle speed. Pressure gauge should show 29 psi (2.0 kg/cm2 ). Disconnect vacuum line at pressure regulator. Pressure gauge should show 33-39 psi (2.3-2.7 kg/cm2 ).
  3. Pinch fuel return line of pressure regulator. Pressure gauge should show a minimum of 59 psi (4.1 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. 3. If good, remove DME relay and bridge terminals No. 30 and 87b. Pressure gauge should show 33-39 psi (2.3-2.7 kg/cm2 ).
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