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Any Thoughts?

5K views 19 replies 9 participants last post by  oefvetw124lover 
#1 ·
How do I change my igniton coils on my W140 (1993 400sel V8) ?

Any thoughts will be appreciated.

Adam
 
#7 ·
No... older models have ditributor(s) which distribute spark to cylinders, ignition coils recieve signal from ecu and send spark. Coils are mounted on top of the cylinders and theres one per cylinder, and v8s have 2 distributors that are mounted off the cams.... these are two different ignition systems, you cant have both.
 
#4 ·
My car is starting to jerk when I try to accelerate (feels like its in limp mode), but ASR light is NOT on.

Have a look at this link (it shows how to change seals and distributors):

http://www.benzworld.org/forums/w140-s-class/1280220-replacing-camshaft-seals.html


Is there anything I should know before doing this?
Things to Avoid?

I'm scared my car won't be able to start after I change these?

What do you guys think?

Thanks,

Adam
 
#5 ·
I think its worth a shot, but id make sure your distributor caps are good, also check your wiring harness. Also what kind of plugs are you using? My uncle has the same exact thing as you and he put 4 way plugs and his car ran like shit. After he put normal copper plugs it ran okay, until his wiring harness corroded....... good luck man!
 
#8 ·
My car was running bad, so I used NGK Platinum spark plugs, and that made my car run good for a week. So I changed the NGK's to Bosch OEM sparkplugs and my car ran good for a few days, but went back to being really really sluggish. Not sure what I should be looking for to decide whether or not my distributor caps are good or bad ?
 
#11 ·
Adam,

You have 2 distributor caps, 2 rotors, 2 coils. When was the last time the caps and rotors were replaced? Coils aren't usually wear items, but they do fail. Before replacing them, it would probably do you well to install new (correct) plugs Bosch F8DC4's, new ignition wires, caps and rotors. The ignition system on your year/model is stone simple and requires only basic components. Pure copper non-resistor plugs (as mentioned above) are spec items. Less than $2 ea. All the fancy, expensive brands out there will only be a pure waste of money. Try your dealer or any one of several online sources for the plugs. They will not be available at retail part store chains. Do not believe what the counter jockey tells you about this or that being a compatible plug.

The coils are mounted next to and behind the ABS pump. Held in place by two retaining nuts. Remove the beauty covers on the left inner side, and you'll see both coils. If your upper/lower wiring harness and ETA haven't been replaced, get ready. It is only a matter of time.

Good Luck

Jayare
 
#12 ·
Thanks for the help Jayare,

Is it possible to post some pictures of where I should be looking under my hood? I'm not very familiar of the location of ABS Pump, or where the coils are (which beauty covers your talking about), etc... Pictures would really get the message across (Pardon my intelligence in W140 :(
How would I know if my ignition rotos/caps are bad ?

Adam
 
#13 · (Edited)
Adam,

What I call the "beauty covers" are the large plastic panels that run along the inside edge of the fenders, under the hood. You want to take off the panels that cover the left side (drivers). Under the forward section, you'll see the coils.

I am not at all aware of your DIY skills or how you are set up with tools. With all due respect, based on your questions it may be best for you to take the car to a qualified independant shop that you have a relationship with. Removal of the caps is a simple affair and only requires a 5MM allen socket. However if you are not mechanically inclined, you may not know what a used up cap looks like on the inside. The same goes for replacing the ingnition wires and rotors.

If you have no idea as to the age or miles on the cap, rotor, wires and plugs, it's time to change them and establish a baseline of service for your car. Likewise for the air/fuel filters, transmission fluid and filter, coolant, power steering fluid and filter, brake fluid.

Jayare
 
#14 ·
Hey Jayare,

Again, I appreciate your help on this, and I understand that I'm not a 'genius' at DIY. That being said, so far, I've changed the following by myself:

- Spark plugs
- Fuel Filter
- Fuel Pump
- All 8 fuel injectors ( which was hard :( but it worked )
- Radiator

So I'm not totally 'stupid' lol , I can do some repairs by myself..

Anyways, back to the original topic:

Here is a picture of the distributor cap:


Here is a picture of the rotor:



I know how to change distributor cap/rotors, but not ignition coils. The reason for that is because I dont really know where they are (again, I could really use some picture-help).

This is a picture I found on the internet (its a picture of s500 engine, which is not my car, but looks almost identical):

Are you talking about removing the cover that is directly behind the DRIVER SIDE headlight ? Not the one to change your headlight bulbs, but the cover directly behind that ?

And yes, I don't think rotors,caps,ignition wires,spark plug wire have ever been changed on this car.. so It's definitely time. Any thoughts of how to change ignition wires/spark wires ? Is it as simple as it looks? I'm guessing I unplug each spark plug wire from both sides and put a new plug wire (remove , plug and play) ? same goes for ignition wires?

Thanks again for your help Jayare, I really appreciate it (the only way i'm ever gonna better my knowledge with W140's is by talking to experts, so thanks again :) )

Adam
 
#16 · (Edited)
You Coil is on the left middle side acsessible from underneat the car,near the oilsump's edge,the red arrows only give you a hint where to look for them from underneat ,it's cover'd by an alloy looking cover that has 2/3 screws to them ,before you start unscrewing the coil's terminals make sure the batterie is disconnected unless you like to see sparks (party time lol) ,make sure you have the radio code handy before disconnecting the batterie .
To see more pictures go here http://www.benzworld.org/forums/w140-s-class/1589355-lower-engine-wiring-harness-v8-s500.html , there is also a diagram you could use on the 1st page .
Make sure the car is jacked up safely, use extra support if you dont know how to ,a rim /wheel, bricks ,look what i did ,the one thing i hate is to work directly underneat this 2.2 tonne monster (lol).
Adam ,if you can change the fuel injectors this is nothing in compare.
Good luck . :thumbsup:

JAYARE: are you sure there are 2 Coils because i only ever see one there , so is the lower harness connection as well since there is only 1 fitting conector for the coil 93 S500 (you got me thinking now ,lol) .
 

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#17 ·
Follow the coil wire from the center of each distributor cap to the coils. Also, take a shot of the inside of the cap and a close up of the rotor. There isn't anything you can determine by looking at the outside. There is no need to remove the rotor mount from the cam. Just the rotor. The engine bay shot you found is of a later model M119 with distributor less ignition (electronic)

Jayare

Sent from my DROID2 using AutoGuide.Com Free App
 
#18 ·
Adam, I had almost the same symptoms as you describe, on my car a 1991 600 sel. The car would run fine for a while and then all of a sudden it would feel like running on 6 cylinders, it would have some kind of shake etc. I changed the spark plugs the problem was fixed for a while. Then one day my car caught fire. Basically the ignition coil had short circuited or something. it started with violent shakes like runing on 6 cylinders. I would check the ignition coil. just my 2 cents.

Here is the full story of what happened to me: http://www.benzworld.org/forums/w140-s-class/1639955-600-sel-caught-fire.html

It may not be the same problem with your car, just please check the ignition coil, better to be safe then sorry.
 
#19 ·
When I started to have problems with my E420 it turned out to be cap and rotors! For some reason that car would eat caps and rotors?? But when I changed them the car ran like a top!!! If yours have never been changed my money is that it is gonna run much better when you get new ones on it!!


Smokie
 
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