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
Preparation For Testing
- Measure resistance values only after turning off ignition or disconnecting battery. Pull off both control unit plugs or make a firm connection between ignition coil terminal 4 and ground with a jumper wire before checking the compression.
- DO NOT replace specified ignition coil with a different ignition coil. DO NOT connect a shielded capacitor on ignition coil terminals 1 and 15. Ignition coil terminal 1 must not be used for ground when installing a burglar alarm system (ignition coil would be destroyed with the ignition switch in the "ON" position).
- DO NOT disconnect ignition lead between ignition coil terminal 4 and high voltage distributor terminal 4 while engine is running. DO NOT allow voltage to jump from ignition coil terminal 4 to ignition coil terminals 1 and 15, as control unit could be destroyed.
- To avoid damage to the ignition control unit, secondary side of ignition system must be shielded with at least a 4000 ohm resistor, and the original distributor rotor with a 1000 shielded resistor must be installed. Pull off plugs on EZF control unit and ignition control unit only after turning off ignition.
- Flashover or disruptive discharge on the distributor cap (poor insulation) could destroy the control unit. Never disconnect battery while engine is running. DO NOT mix up power supply connections or make wrong connections on battery. This could damage the LH-Jetronic control unit, ignition coils and EZF control unit. DO NOT use more than 16 volts to start engine.
Factory Service Tools
Use the Manual With the Right Hardware
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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.