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Home >> Porsche >> 1985 >> 928 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - BOSCH LH >> Testing >> Test 20 >> Fuel Pressure
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Fuel Pressure

  1. Unscrew cap nut on end of the injection line. Be careful that sealing does not fall out. Connect Pressure Tester (P 378 or VW 1318) on adapter. Start engine and run at idle speed. Test pressure should be 29 psi (2.04 kg/cm2 ).
  2. Clamp return hose of pressure regulator slowly with a hose clamp (on fuel level transmitter). If pressure is less than 58 psi (4.8 kg/cm2 ), check fuel filter and replace fuel pump, if necessary.
  3. If engine will not run. Pull off relay "XX" and bridge terminals 30 and 87 on socket. Fuel pump should run. Fuel pressure should be 33.3-39 psi (2.3-2.74 kg/cm2 ).
  4. If engine is hard to start with at operating temperature, check pressure regulator for leaks. Check fuel pump check valve for being defective. Check fuel injectors for leakage.
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