Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1985 Porsche 928 AutomaticFACTORY OEM SERVICE PROCEDURE
Fuel Pressure
- 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 ).
- 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.
- 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 ).
- 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.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.