300 Going through dizzy caps???

Hello Lenny,

The obvious place to check for me would be the spark plugs heat range and gap. If the gap is bigger than it ought to, your igniton pack is turning up the current to the coil thinking it has a high resistance. The high current could be burning the carbon in the distributor cap. Make sure you are using the correct spark plugs; if you have modified to use multi-core plugs or platinum tipped plugs, make sure they are the correct ones'.

Check the HT lead and connections between the coil and distributor tower, are these pushed in good and proper? Is the lead fine? Then check the rest of the leads, have thes voltage and resistance checked on an oscilloscope. Is the coil the right one for the vehicle?

Are you using Mercedes ignition leads or are these after market? I know M/Benz one are expensive but well worth paying the price for them. These leads come in parts of three per lead. The spark plug end, the lead and the distributor end. These screw on and resistance can be checked as a whole lead and if you get a high reading the parts can be unscrewed and relevant parts replaced as necessary. A word of warning, unscrewing an old lead could snap off an end, in which case a dealer has equipment to either fit a new end or persuade you to buy a new lead. 

A long shot, check and clean the base of the ignition module for good earthing. You will need to apply a special paste to the base before re-fitting. I do not know what it is called but you should be able to buy from a dealer.

Do keep us posted.

Hello Lenny,

If the leads and spark plugs are fine as you say, do make sure the leads are pushed in the towers at the distributor and coil.

Would you PM me your chassis number and if you can, any numbers from the coil and ignition pack. 

I must say, I have never heard of any issues for the distributor prematurely burning out; I will make enquiries.

Have your charging rate checked, I am persuming if the charge rate is high, the coil may be getting high input hence, output a high discharge. 

Copy me on the PM Lenny and i will help Rakesh with his research

No luck with selling it yet then!

Gav

Hi Lenny

Here is a list below of the part numbers that apply to your chassis number.

Hopefully you can check that you have the correct set up.

I have only 2 comments from experience…

I have seen on a few occasions damage to the Bracket that the Rotor Arm screws onto, on the end of the Camshaft, bent and or cracked in most cases. Probably through over tightening of the 3 screws that hold the Rotor Arm on, worth just checking on.

Also my view on the Bosch replacements products, and all OE quality suppliers, although the parts are of reasonable quality, I would always be fitting the genuine MB Cap and Rotor if you could afford it. It is easy for me to say this from my sofa in the Yorkshire countryside and I have no possible guarantee that it will cure your truck! But from experience the MB items are of better quality.

This I guess will not stand up in a court and I remember MB getting into hot water with a supplier a few years back for stating that the MB version of the suppliers product was different and better than the one supplied as an aftermarket OE item and that the MB ones had gone through a more stringent quality control and the rejections found their way into the OE parts network. What I can tell you is that MB constantly develops parts and over the years will modify them as issues or problems arise or manufacturing techniques change. When you buy the MB part you always get the latest version. This is not so if you go and buy an OE quality part made by the OE supplier. This could be any one of the earlier versions and may or may not really be up to the job.

Think of it like Microsoft and Windows….

The MB Genuine item will always be the cutting edge Windows 8…

The OE supplier might be supplying Windows 7, XP or 95 or 3.0, you just don’t know!!!

You could buy a new part that has an inherent failure built in that the latest MB item has had it fixed, it will be cheaper for a reason, and there are no real bargains anymore, in effect your buying New Old Stock.

Obviously this will be OK for some parts, but any safety critical items or items that could damage the drivetrain or cause repeated failures and breakdowns, sometimes even causing collateral damage should in my opinion be avoided.

Anyway….enough of the sermon….

Distributor Cap – A103 158 00 02 X1

Rotor Arm – A103 158 03 31 X1

Spark Plug – A003 159 05 03 X6

Suppressor Plug End – A000 156 54 10 X6

Distributor Cap End – A000 159 28 42 X7

Coil Cap End – A000 159 29 42 X1

Brass Crimp Screw End - A000 159 14 38 X14

Plug Lead Cable – A110 159 18 18 X4mtr

No1 – 340mm

No2 – 420mm

No3 – 580mm

No4 – 580mm

No5 – 740mm

No6 – 870mm

Coil Lead Cable – A115 159 08 18 X1mtr

Coil – A000 158 50 03 (Original) – A000 158 62 03 or A000 158 53 03 (Latest)

EZL Unit – A008 545 36 32

Cam Drive Bracket – A103 158 08 40

Cam Drive Dust Cover – A103 158 00 88

Cam Drive Seal – A014 997 58 48

Distributor Cap Cover – A103 158 05 85

Cheers

Gav

some of us prefer XP

....or OSX 

Spider1V

Specifically Mountain Lion 

Some of us live in the 21st Century

I would renew the rotor arm, yours is tracking and also clean or replace the yellow disc shield and seal seen in photo 2. JPG. I do not know what the other side of the shield is like and cannot say from the photo if I am looking at tracking marks or dirt.

The distributor cap can be re-used, just clean the carbon from the terminals; lightly scrape using a flat blade screw driver.

Clean and wipe the rotor arm base or shoe, the metal part the rotor is attached to.

If you do have your reciept from where you had bought the rortor from, without cleaning the rotor take it back and claim under warranty, if it is less than months or have done less than 6000 miles with this rotor.

I had the same problem the year before last when the dizzys in my g-wagen and my w124 both went with in a couple of weeks of each other, I carry spares of them now

I'm sure it's not the case but for the record my experience with distributor cap problem was related to water pump front seal leak.

Water pump front seal leaked and sprayed the cooland all over the place including dizzy cap area. Result - syrup like drops inside the dizzy cap. First they looked like water drops but i tried to wipe them of they were sticky syrup-like. Most likely the coolant entered the dizzy cap through vent holes in form of fume and condensated on the cap surface.

Changed the water pump, cleaned the dizzy cap and it worked as it should.