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New Ignition Wires, Rotor and Distributor Cap
 
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Pelican Technical Article:

New Ignition Wires, Rotor and Distributor Cap

Steve Vernon

Time:

2 hours2 hrs

Tab:

$200

Talent:

**

Tools:

Flathead screwdriver, spark plug socket and driver, torque wrench

Applicable Models:

Mercedes-Benz W126 (1981-91)

Parts Required:

Wires, Plugs, Rotor and Distributor cap,

Hot Tip:

Work on a cold engine

Performance Gain:

Cleaner running engine

Complementary Modification:

Check your timing

One basic tune-up procedure for just about any car on the road is the replacement of your spark plugs and spark plug wires. I recommend examining and/or replacing your spark plugs every 30,000 miles, or about once every other year. In reality, you can probably go longer than that, (most manufacturers recommend an interval of 100,000 miles) but, you never really quite know how long the plugs are going to last. A lot of factors can contribute to the plugs wearing out faster than you might expect especially as the car ages. Another part you should check is the distributor cap and rotor. In this article, we will show you how to replace your rotor, distributor cap, wires and plugs.

Begin by prepping the car. The only thing that you really need to do is to make sure that the car is cold. If you try to remove or install spark plugs in a hot car, then you may encounter problems with the spark plugs gumming up or damaging the relatively delicate threads in the aluminum cylinder heads. Make sure that the car is cold, or at the bare minimum, only slightly warm to the touch.

This article assumes that your engine has been running fine and that you are not having a timing issue. If you do not disturb the rotation or placement of the distributor itself you do not need to worry about setting the engine to top dead center and resetting the timing.

If you are only changing the plugs and rotor, it is a good idea to label the wires so you will know which goes on which. Begin by removing the air cleaner housing on the top of the engine. You could probably do the job without removing it, but the thing is huge and it makes everything simpler with it out of the way. Begin by sliding the air inlet tube away from the radiator and remove. Next undo the six clips holding the lid on as well as the wing nut in the center of the air cleaner housing. With the lid removed remove the air pump hose on the right side. Remove the two wing nuts (one on each side) attaching the air housing cover to the valve covers. Lift the housing off the motor minding the EGR hose bellow and taking care not to drop any dirt or debris into the metering plate.

With the air cleaner housing removed grab the wires by the boot and turn them slightly and pull straight out. Do not attempt to pull them out by the wires as there is a pretty good chance you will just rip the wire from the boot. The wires should be routed through a wire holder on the top of each valve cover. The right bank of wires also goes through a bracket attached to the cruise control support bracket. Use a 10mm wrench and remove it to remove the wires.

Remove the wire from the coil and feed it back through the engine bay so it can be removed with the distributor cap.

Remove the two bolts holding the distributor cap to the distributor. Use a large flat head screw driver, push the screw down and give it a half turn, it will pop up when released. You can now remove the cap and wires as one piece. Check the cap for dark and charred scorching on the inside; this can be signs of arcing meaning they may be a problem with the vacuum advance on the distributor.

With the cap off you can remove the rotor. There is a guide key that the rotor fits into that lines it up, do not try and force the rotor on any other way than sliding it into the guide key. Replace the dust seal on the dust cap while you are there.

Remove the old plugs and check for any signs of an unhealthy engine. Burnt, wet or oily plugs are all signs of engine trouble and should not be ignored. Typically, you want to see a slightly tan, burnt appearance. This will indicate that your engine is running normally. A really good idea when working around your plugs is to tape your socket and extension together. There is a small rubber grommet inside the spark plug socket that helps hold the plug in place while in a vertical position, this grommet also has a tendency to separate the socket from the extension when you don't want it to and will leave you fishing out your socket with needle nose pliers. Slide the extension all the way down until you feel the socket firmly grip the spark plug. The spark plugs should be tight in the cylinder head, but not overly difficult to remove with a little force. Install your new plugs and torque according to your engine specs.

I don't recommend using anti-seize compound on your plugs as the theory is that the anti-seize tends to act as an electrical insulator between the plug and the cylinder head. This could have detrimental effect on the firing of the spark due to the loss of a good, consistent ground connection.

Installation is the reverse of removal.

Begin by sliding the air inlet tube away from the radiator (red arrow) and remove.
Figure 1

Begin by sliding the air inlet tube away from the radiator (red arrow) and remove.

Undo the six clips (red arrows) holding the air housing lid on as well as the wing nut (green arrow) in the center of the air cleaner housing.
Figure 2

Undo the six clips (red arrows) holding the air housing lid on as well as the wing nut (green arrow) in the center of the air cleaner housing.

With the lid removed remove the air pump hose (red arrow) on the right side.
Figure 3

With the lid removed remove the air pump hose (red arrow) on the right side.

Remove the two wing nuts (red arrow, one on each side) attaching the air housing cover to the valve covers.
Figure 4

Remove the two wing nuts (red arrow, one on each side) attaching the air housing cover to the valve covers.

Lift the housing off the motor minding the EGR hose (red arrow) bellow and taking care not to drop any dirt or debris into the metering plate.
Figure 5

Lift the housing off the motor minding the EGR hose (red arrow) bellow and taking care not to drop any dirt or debris into the metering plate.

This photo illustrates where the EGR hose connects (red arrow).
Figure 6

This photo illustrates where the EGR hose connects (red arrow).

With the air cleaner housing removed, grab the wires by the boot and turn them slightly and pull straight out (red arrow).
Figure 7

With the air cleaner housing removed, grab the wires by the boot and turn them slightly and pull straight out (red arrow). Do not attempt to pull them out by the wires as there is a pretty good chance you will just rip the wire from the boot.

The wires should be routed through wire holders (red arrows) on the top of each valve cover.
Figure 8

The wires should be routed through wire holders (red arrows) on the top of each valve cover.

The right bank of wires also goes through a bracket attached to the cruise control support bracket (red arrow).
Figure 9

The right bank of wires also goes through a bracket attached to the cruise control support bracket (red arrow). Use a 10mm wrench and remove it to remove the wires.

Remove the wire from the coil (red arrow) and feed it back through the engine bay so it can be removed with the distributor cap.
Figure 10

Remove the wire from the coil (red arrow) and feed it back through the engine bay so it can be removed with the distributor cap.

Remove the two screws holding the distributor cap to the distributor (red arrows).
Figure 11

Remove the two screws holding the distributor cap to the distributor (red arrows). Use a large flat head screw driver, push the screw down and give it a half turn, it will pop up when released.

You can now remove the cap and wires as one piece.
Figure 12

You can now remove the cap and wires as one piece.

Check the cap for dark and charred scorching on the inside of the cap (red arrow); this can be signs of arcing meaning there may be a problem with the vacuum advance on the distributor.
Figure 13

Check the cap for dark and charred scorching on the inside of the cap (red arrow); this can be signs of arcing meaning there may be a problem with the vacuum advance on the distributor. This cap looks used, but fine.

With the cap off you can remove the rotor.
Figure 14

With the cap off you can remove the rotor. There is a guide key that the rotor fits into that lines it up (red arrow), do not try and force the rotor on any other way than sliding it into the guide key.

Replace the dust cap (red arrow) while you are there.
Figure 15

Replace the dust cap (red arrow) while you are there. The green arrow shows the vacuum line from the vacuum advance.

Remove your old plugs and install new ones (red arrow).
Figure 16

Remove your old plugs and install new ones (red arrow).

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Comments and Suggestions:
jay Comments: Hi need to know how to reset the distrubuter in the correct position so dat firing order can be correct
March 21, 2016
  Followup from the Pelican Staff: See this tech article: http://www.pelicanparts.com/techarticles/Mercedes-W126/11-ELEC-Replacing_Your_Distributor/11-ELEC-Replacing_Your_Distributor.htm - Nick at Pelican Parts  
dcw137 Comments: I Think that is why you label wires. Then put the cap on by itself it should feel secure.
May 22, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
gmkjr Comments: Rather than removing the wires & cap as a unit, I suggest that you leave the old cap cap next to the distributor, the replace the wires one-at-a-time, so that as you install the new wires, you follow the same pattern as the old wires. There is something of an art to arranging the routing of the new wires across to distributor cap so that they look neat and will be flexible enough to r/r the distributor cap.

Reportedly, one way to determine if you need new wires is to stop the car in a dark place, and look at the wires with the engine running to see if there is any arc-ing from the wires to the engine. If you see arc-ing, you need new wires. I don't know if this is an accurate way to determine if you need new wires.
February 20, 2015
  Followup from the Pelican Staff: I agree, that is a good tip.

Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Rolando Comments: your illustration is great for the Benz 420 SEL and mostlikely others ??
here it is when replacing the distributor ROTOR=

when you pull it out the shaft will then turn back into position 8 aprx.
so when liding the the new ROTOR into the lot
sensor Positioning shaft
then when pushed all the way into the slot
YOU MUST TURN THE ROTOR CLOCKWISE AND THEN IT WILL SNAP IN AND GOES DOWN PULLED TOWN BY THE SHAFT,
IF YOU ARE NOT DOING THAT FIRS T U MAY NOT GET THE DISTRIBUTOR BACK ON,
SECFOND IF U FORCE THE SREW BACK IN U WILL MOS T DEFENENTLY CRACK THE THE CAP
OR LATEST WHEN U TURN THAT CAR ON

SO PUSH IT INTHE SLOT THEN TURN THE ROTOR CLOCKWISE INTO POSITION 1 ,, THANKS
LEARNED THE HARD WAY
SHOULD BE EXPLAINT ON EVERY DISTRB, ROTOR
THANKS YOU FOR THE REST OFF THE GOOD TIPS
ROLAND BUHLER nyc QUEENS
October 12, 2013
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
 

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