Distributor Cap and Rotor Replacement

Overview

This procedure outlines how to remove and replace the distributor cap and rotor on a Porsche 944 S / S2 with a 16v engine. The distributor cap directs electrical current to the spark plugs, and the rotor spins inside to distribute that current. Replacing these parts is essential for maintaining proper ignition timing and engine performance. This can be a tricky job due to the unique locking screws, but with the right approach, it becomes manageable.

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Tools Required

• 1/8 inch or 3mm hex key
• Long, thin flat-tip screwdriver (e.g., Snap-On SDD1416 with a 16 inch blade or MATCO SCM818P2)

Parts Required

• Distributor cap – 944 602 901 00
• Rotor – 944 602 902 00
• Rotor retaining screw (if needed) – 900 075 091 02

Step-by-Step Procedure

1. Removing the Distributor Cap

1. Locate the distributor cap on the front of the 16v engine, near the exhaust manifold side.
2. Using paint or nail polish, mark the bottom half of the top locking screw and the top half of the bottom locking screw. This helps you track their position.
3. Take a long, thin flat-tip screwdriver (like a Snap-On SDD1416). Place a towel on the nose panel lip to protect the paint, then rest the screwdriver blade against it at an angle.
4. Push in on the bottom locking screw and turn it clockwise 270°. The painted half of the screw head should now point toward the exhaust manifold side.
5. Push in on the top locking screw and turn it clockwise 90°. The painted half should also point toward the exhaust manifold side.
6. Gently pull the distributor cap off. It should slide out easily if the screws are aligned correctly.

2. Removing the Rotor

7. Find the rotor inside the distributor housing, attached to the camshaft extension.
8. Use a 1/8 inch hex key to remove the retaining screw. If it’s too big, switch to a 3mm hex key. (Note: Original screws are slightly larger than 3mm and may be loctited—start with 1/8 inch to avoid stripping.)
9. Twist the rotor to remove it. If it’s stuck, it may have bonded to the camshaft. You might need to break it off carefully—use channel lock pliers on the metal sleeve inside if necessary, as the rotor’s Bakelite material is brittle.

3. Installing the Rotor

10. Slide the new rotor (944 602 902 00) onto the camshaft extension.
11. Insert the retaining screw (900 075 091 02) and tighten it with a 1/8 inch or 3mm hex key. Hold the screw carefully to avoid dropping it into the distributor housing.

4. Installing the Distributor Cap

12. Hold the new distributor cap (944 602 901 00) in its normal position (one screw on top, one on bottom).
13. Turn both locking screws so their 90° tips point left (looking at the front of the cap).
14. Mark the left half of each screw head with paint or nail polish to track their position.
15. Slide the cap onto the distributor housing, centering it over the rotor. The screw tips should fit easily into the elongated holes.
16. Using the flat-tip screwdriver, turn the bottom locking screw 270° counter-clockwise. The painted half should now point up toward the center of the cap.
17. Turn the top locking screw 90° counter-clockwise. The painted half should point down toward the center of the cap.
18. Reconnect the spark plug wires to the distributor cap in the correct firing order for the 16v engine (1-3-4-2).

Post Procedure Checklist

• Ensure the distributor cap is securely locked in place and doesn’t wiggle.
• Check that the rotor spins freely when turned by hand (before installing the cap).
• Verify all spark plug wires are firmly connected and in the right order.
• Start the engine and listen for smooth operation—no misfires or rough idling.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube