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Distributor Cap, Rotor and Wires Removal
 
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Pelican Technical Article:

Distributor Cap, Rotor and Wires Removal

Kerry Jonsson

Time:

3 hours3 hrs

Tab:

$350

Talent:

***

Tools:

3mm, 5mm Allen head sockets, pliers

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Distributor cap, rotor, spark plug wires

Hot Tip:

Replace each wire one at a time and route it properly

Performance Gain:

Smoother running engine, extended engine life

Complementary Modification:

Change the spark plugs at the same time

Once the ignition module triggers the coils the high energy ignition passes through two coil wires to the distributor cap. From the center of the cap the high energy voltage passes through an ignition rotor to the outer distributor cap towers. From there the high energy ignition voltage passes through the spark plug wires to the spark plugs where it ignites the air/fuel mixture. Over time these components can wear as the spark arcs across contacts. Spark plug wires can become brittle with engine heat and age. If cracks develop in the spark plug wires the high energy ignition can take the easier path and arc to ground. When this happens the cylinder will not fire and you will have a rough running engine. In this tech article we will go over all the steps to replace your distributor cap, ignition rotor and spark plug wires.

Make sure the car is off and the keys are out of the ignition before you start working.

ThisPicture illustrates the number one coil that fires the right side bank of cylinders numbers one through four.
Figure 1

ThisPicture illustrates the number one coil that fires the right side bank of cylinders numbers one through four. Twist the coil wire first before attempting to pull it off of the coil tower.

ThisPicture illustrates that we are at the number two coil that fires the left side bank of cylinders, numbers five through eight.
Figure 2

ThisPicture illustrates that we are at the number two coil that fires the left side bank of cylinders, numbers five through eight. Once again twist the coil wire first before attempting to pull it off of the coil tower.

ThisPicture illustrates the front of the right side cylinder head.
Figure 3

ThisPicture illustrates the front of the right side cylinder head. Place your fingers under the bottom of the distributor cap cover and pull outward and upward. This will unlock the clip and allow the cover to slide upward. You will have to perform these same steps on the left side cylinder bank if you are changing the distributor cap and rotor.

Continue to slide the cover upward noting the position of the locating tab so you can put it back in the same place during installation.
Figure 4

Continue to slide the cover upward noting the position of the locating tab so you can put it back in the same place during installation.

Now working at the front of the right side cylinder head looking at the distributor cap, you can remove the distributor cap while leaving the spark plug wires attached or you can remove all of the spark plug wires.
Figure 5

Now working at the front of the right side cylinder head looking at the distributor cap, you can remove the distributor cap while leaving the spark plug wires attached or you can remove all of the spark plug wires. Remove the three 4mm Allen head fasteners (green arrows) hidden behind the spark plug wires. One of them is hidden recessed under the distributor cap (yellow arrow) As you can see here the wires have a numbered tag on each one to identify what cylinder they are routed to. If you are worried about mixing up the wires simply replace each plug wire one at the time.

Here is a close up view of the distributor cap wiring.
Figure 6

Here is a close up view of the distributor cap wiring. Notice the white tabs that identify the cylinder numbers so that you cannot improperly route the spark plug wires. Cylinder and number one (green arrow), cylinder number four (yellow arrow), cylinder number six (blue arrow) and cylinder number seven (red arrow).

ThisPicture illustrates a close up view both the left side cylinder bank distributor cap.
Figure 7

ThisPicture illustrates a close up view both the left side cylinder bank distributor cap. Cylinder number three (green arrow), cylinder number two (yellow arrow), cylinder number five (blue arrow) and cylinder number eight (red arrow).

ThisPicture illustrates the front of the left side cylinder head.
Figure 8

ThisPicture illustrates the front of the left side cylinder head. You can use a pair of pliers to squeeze the top of the spark plug wire. Twist the spark plug wire first before attempting to pull it off of the distributor cap.

With the distributor cap out of the way remove the three 3 mm Allen head fasteners (green arrows) that hold on the ignition rotor.
Figure 9

With the distributor cap out of the way remove the three 3 mm Allen head fasteners (green arrows) that hold on the ignition rotor.

Pull the ignition rotor off the end of the driver flange.
Figure 10

Pull the ignition rotor off the end of the driver flange.

ThisPicture illustrates the right side cylinder head with the ignition wire cover removed.
Figure 11

ThisPicture illustrates the right side cylinder head with the ignition wire cover removed. Pull out each of the spark plug wires from their spark plugs. If you're worried about mixing up the wires replace only one spark plug wire at the time.

The spark plug wires are routed in plastic sheathing.
Figure 12

The spark plug wires are routed in plastic sheathing. The wires are held in place by plastic clips. Place a small flatblade screwdriver under the clip and lever it off. Both sides of the clip can come off and the clip can go flying. Hold it in place while removing so you don't lose it.

Once the clips are removed you can start removing the spark plug wires from the plastic sheathing.
Figure 13

Once the clips are removed you can start removing the spark plug wires from the plastic sheathing. You may want to replace each wire one at a time or if you feel comfortable you can remove all of them and route the new wires individually. You will have to route the wires underneath brackets and linkages to get them to their proper location. Once the wires are at their proper location fit them into their spark plug holes and press down firmly on them to make sure the clip on the spark plugs. At the other end of the wire properly position them on the distributor cap. Fit the ignition rotor and tighten down the three fasteners. Install the distributor cap and tighten down the three fasteners. Route the coil wires to their proper coil and fit them on to their coil towers. Install the spark plug wire covers on the valve cover and install the distributor cap covers on the front of the cylinder heads. Start the engine and verify that it runs smooth.

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Comments and Suggestions:
Bobby Comments: Headlight with housing for 1990 mercedez benz 500 sl
March 12, 2015
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