[W126 Coupe] Opinion on ignition parts & dust cover

[Richard Hogarth]

    Opinion on alternate branded ignition parts: 
I've been working on cars since I was 13years old and I'm 49 now and I have
rarely found alternate ignition parts to make anything but subtle
differences in the running of an engine. I've had shorted and open-circuited
plugs and rotors and caps from every manufacturer. If a box of plugs gets
dropped on the ground before it gets to you, it's likely that at least one
of those plugs will have fractures in the ceramic insulator. The result of
that could make great super expensive plugs perform like garbage. One plug
that for me was pure fraud and poor design from the get-go was the "split
fire plug". Every set that I tried in multiple vehicles always caused
problems. Blister pak plugs from Walmart of any manufacture are also
consistent losers. I have some guesses as to why that is so but no hard
evidence. There were also some "plastic" replacement dist. caps  and rotors
made to replace Bosch parts that were also consistent crap. Luckily those
Mex and Chinese import parts are long gone. 
A genereal rule of thumb is to use a cap and rotor of the same age and same
manufacturer. This is because the air gap between the rotor contact and the
cap contact is as important as the plug gap and these gaps will only be to
tolerance if parts are from the same manufacturer. 
    I'm running a Neihoff cap (from NAPA) , Neihoff rotor, and Bosch plat 2
plugs in my '91 560sel and I have smooth sailing all the up to 130mph.
I could not justify spending $100.00 on a new cap and $55 on a new rotor. 
If the engine is that sensitive to the cap / rotor / plug combos - it is
likely that other things are not right elsewhere in the system.
Electronic ignition systems are extremely robust and forgiving with respect
to the aging of ignition parts like the cap/rotor/plugs. 
Ignition wires (thigh tension cables) are another strory all together with
huge performance differences among different designs. 
 
    About the dust and moisture cover:
The dust and water cover that goes in the distributor is not a
super-critical part. If the internal dust cover is disintegrating - make
sure to remove it so that the bits and chunks of plastic that crumble don't
interfere with the mechanical advance in the lower section of the
Distrributor. Those dust shields are insanely priced from the dealer at
something like $47.00. If someone knows of a less expensive source, I'd sure
like to know about it. 
-Richard Hogarth
 

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From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Dick Spellman
Sent: Wednesday, September 14, 2005 12:04 PM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] Tune up woes


I removed cap and rotor and they look fine.  He's missing the inside
distributor cover that sits below the rotor which I told him to order just
because it has a place and reason for being there.  I'll tell you I had this
same problem on a 300SE I bought last November.  It had a new mongrel cap
and rotor and I had this pause on acceleration and an occasional miss at
speed.  I changed up to Bosch OEM cap, rotor and plugs plus put in the same
wire set this fellow now has and all was cured.
 
I asked about the fuel filter but he has no record of it ever being changed.
I'll tell him to add this to his list.
 
What do you guys think about the cap and rotor.  Re the plugs, I agree with
Richard, they have to be changed to OEM.
 
Dick

----- Original Message ----- 
From: Richard Hogarth <mailto:R_Hogarth at Foundrycove.com>  
To: 'Mercedes Coupes Mailing Lists' <mailto:mbcoupes at mbcoupes.com>  
Sent: Wednesday, September 14, 2005 12:54 PM
Subject: RE: [W126 Coupe] Tune up woes

Sounds like fuel starvation. 
Change the fuel filter asap to start with. 
-Richard Hogarth

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From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Shayegan, Richard
Sent: Wednesday, September 14, 2005 11:49 AM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Tune up woes



Isn't this exactly why people say stick to the W9DC plugs?

 


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From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Dick Spellman
Sent: Wednesday, September 14, 2005 12:45 PM
To: mbcoupes at mbcoupes.com
Subject: [W126 Coupe] Tune up woes

 

A fellow SEC type with a 500 engine had the work performed to fix a backfire
problem by a local (non-MB) shop.  They installed new wire set (the brand
and set-up are just fine), a new cap and rotor (both mongrel aftermarket not
Bosch) and new plugs (my friend thinks they have 2 electrodes or more).

 

Anyway, the car starts and runs fine but, when on the highway doing 70 or so
the engine just quits momentarily and then kicks back in.  This all started
1,000 miles after the tune-up. 

 

What are your thoughts on a path to diagnosing the problem? Regards,


Dick



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