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Pelican Technical Article:

Ignition Coil Removal

Kerry Jonsson

Time:

1 hour1 hr

Tab:

$225

Talent:

*

Tools:

6mm, 8mm, 10mm socket with ratchet, swivel and extensions

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Ignition Coils

Hot Tip:

Twist the coil wire first before removing from coil

Performance Gain:

Repair engine running on one bank or no start

Complementary Modification:

Replace spark plug wires

On the Mercedes Benz 500SL and SL500 they use two ignition coils that generate spark and is sent through two coil wires to both the left and right side distributor caps. The distributor caps and wires are synchronized to distribute high energy voltage to the correct cylinder at the correct time. If one of the coils were to fail the engine could only run on 4 cylinder which is possible but dangerous. On CIS and port fuel injected engines fuel will continue to spray into the cylinders. This will eventually wash down the cylinder walls and cause excessive engine wear. Also, raw fuel will pass through the combustion chamber and will ignite if the catalytic converter is hot from running. On a cold engine the fuel will simply flow through the exhaust and out the tail pipe. In this tech article we will go over all the steps to replace the two ignition coils. They are directional so there is a left side and a right side coil so keep that in mind during installation.

You do not have to remove the air intake duct on the left side of the engine compartment but we have done so for photographic purposes.  If you decide to do if it does give you more room to work.

ThisPicture illustrates the left side of the engine compartment.
Figure 1

ThisPicture illustrates the left side of the engine compartment. Start by pulling the first coil wire off of the ignition coil mounted on the side of the ABS hydraulic assembly. Twist the wire first to break the grip of the rubber on the coil tower.

The second ignition coil is mounted on the inner fender next two ABS hydraulic assemblies.
Figure 2

The second ignition coil is mounted on the inner fender next two ABS hydraulic assemblies. It's in a tight spot. Twist the coil wire first then pull upwards to remove it from the coil.

ThisPicture illustrates the top of the first coil.
Figure 3

ThisPicture illustrates the top of the first coil. Remove the 10 mm fastener (green arrow) on the positive terminal of the coil. Also remove the 8 mm fastener (yellow arrow) on the negative terminal of the coil.

ThisPicture illustrates the top of the second coil.
Figure 4

ThisPicture illustrates the top of the second coil. Remove its 10 mm fastener (green arrow) on the positive terminal of the coil. Also remove the 8 mm fastener (yellow arrow) on the negative terminal of the coil.

ThisPicture illustrates the top of the first coil.
Figure 5

ThisPicture illustrates the top of the first coil. Remove the two 10 mm fasteners (green arrows) that mount the first coil to its bracket. Don't forget to fit the ground strap on the left side bolt during installation.

Remove the first ignition coil from the engine compartment.
Figure 6

Remove the first ignition coil from the engine compartment.

ThisPicture illustrates the second ignition coil.
Figure 7

ThisPicture illustrates the second ignition coil. Remove the two 10 mm fasteners that hold it on to the inner fender. A ratcheting wrench works great here.

It is a very tight fit to get the second ignition coil out of the inner fender.
Figure 8

It is a very tight fit to get the second ignition coil out of the inner fender. You can do this by holding the ABS wiring harness out of the way and the flexing the first brake line out of the way. This gives you just enough room to pull the ignition coil out. Installation is the reverse of the removal steps. Position the coils and install the two mounting fasteners that hold the coils in place. Fit the wiring harness to the positive and negative terminals of each coil and tighten down there fasteners. Finally fit the coil wires and crank the engine to verify it starts.

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Comments and Suggestions:
Elisa Comments: I have a 1992 500sl it is only running on 4cylanders, I was told coils were good and it is the ignition module how can I be sure it is the ignition modue before I go spending money?
October 18, 2015
  Followup from the Pelican Staff: Confirming the module is getting signal to fire coils from DME, but is not doing it. - Nick at Pelican Parts  
Mbzgurl Comments: The part numbers are different. One for the left side, and one for the right side. And, Itried the online service manuals. None of them had what I need online. I'll call. Thanks!
April 25, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
Mbzgurl Comments: The W124 500E has 2 coils. It's the same engine as the SL500. I think I have to remove the left headlight to get to one of the coils. I'm not sure if that is the coil I bought the part for. Might be the other one, but I need a diagram showing me where they are exactly. and wht tools I need, and if there is any percautions to watch out for like wiring.
April 25, 2014
  Followup from the Pelican Staff: We don't currently have that tech article. I would suggest grabbing a repair manual. It will have locations, special tools and torque specs.

I would assume both coils are the same part number. Give our parts specialists a call at 1-888-280-7799. They can tell you if this is the case. - Nick at Pelican Parts
 
Mbzgurl Comments: Would the coils in a 1992 W124 500E be located in the same spot as the 129?
If not, how do I find out? Can’t find any info on the W124 pages. I have one new coil part # 221 502 433. Can’t remember which side I ordered it for.
Thanks.
April 24, 2014
  Followup from the Pelican Staff: I believe a W124 has a single coil. Remove the engine cover, then follow the spark plug cables to the coil. - Nick at Pelican Parts  

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