[W126 Coupe] Vacuum problem?

[David Fatovic]

Well, here is an update as to what is going on with
the SEL.  My dad came up to Breckenridge this weekend
for my "future" brother-in-law's wedding.  He said it
was running sluggish, which I knew, but when he went
to bring the car around the hotel the day of the
wedding to pick up my mom and the car dies!  Can't
start it, nothing.  So Sunday I went to see what was
going on.  On first crank it sounds like there is no
spark.

Pop the hood and start checking the wires.  The wire
going from the coil to the distributor has a kink in
it, that kink is very soft and bubbled out.  I figure
that is the problem, that coil wire is busted and no
spark is getting to the cap.  Well, that was fun
trying to find plug wires in a small mountain town.  

So we try to jerry-rig something and it doesn't work. 
Today we have the car towed down to Denver to the shop
(the forklift dealership the inlaws own).  I decided
to get a new set of plug wires, and a new set of
plugs, replace those.  Good to go on that, we decided
to pop the cap to check the rotor.  The tip was blown
at the tip!  So we replaced that too.  

After new plugs, new wires, and a new rotor, we try to
crank it again.  Again, nothing.  From what we can
tell the coil is getting good power too it, but when
we put a test light on the negative post, it doesn't
flicker but just stays on.  We think the problem is
the coil isn't being grounded and dumping the charge
to the cap.  

Has anybody else had this problem?  Has anybody had to
change the controller that mounts on the fender? 
Bosch Part number 0 227 100 042 or MB Part number
0025452623?  I went to get the one off of my 91, but
it is completely different!  

Any ideas, it looks like the coil is not dumping the
charge and we are not getting spark.

Thanks,

David

--- Dick Spellman <spell.yy at verizon.net> wrote:

> Hi David:
> 
> I am assuming your rough idle and so on are with the
> engine at operating
> temperature.  Could be a few things.  Vacuum as you
> suggest which can be
> located on an idling engine using either propane
> seeping from a torch nozzle
> (not lit) carefully laid around the intake manifold
> or spray carb cleaner
> looking for the engine to smooth out.
> 
> Could be bad ignition wires made worse from the
> power wash.  Easy to check
> after dark to see the sparks jump.  First one to
> check is the coil wire to
> see if it's arcing to the chassis.  Then observe
> each spark plug wire run
> for arcing to chassis or to one another where they
> are bundled or cross.
> Could also be moisture under the distributor cap
> (less likely) but, easy to
> check.  Could also be a loose spark plug or plug
> wire to one of the
> cylinders.  Engine off, push pull each plug wire cap
> to see if any are loose
> and with plug wire removed just check with a socket
> over the spark plug and
> your fingers to see if any are not snugged down.
> 
> A more exact test would be to pull one plug wire
> from each spark plug at a
> time with engine running until you identify which
> wire removal does not make
> the engine run worse.  You'll need to be careful
> when pulling the plug wires
> with engine running not to get jolted.  I use a pair
> of insulated lineman
> pliers and grab the connector not the wire when
> pulling so as to not damage
> a good wire in the process.  You'll feel the engine
> worsen when a good wire
> is pulled.   Just replace it knowing it's good and
> go on to the next one.
> Eventually you'll find the one that makes no
> difference in performance.
> That's the wire or plug you need to inspect/replace.
> 
> Is there a chance you disturbed material in the air
> intake under the air
> metering plate by spraying this area hard with
> water?  This would foul a
> valve or two until it clears out.  One can of BG44K
> ($18 or so) in the fuel
> would clear this up.
> 
> I wash my engines all the time using Degreaser and
> concentrated spray from a
> garden hose.  I avoid the electronics in between the
> fire wall with direct
> spray. I avoid hard spray on the alternator although
> I clear any signs of
> oil build up on that side of the engine near the
> tensioner and front seals
> so I can see if there is an oil leak needing
> attention after a few miles of
> driving on the cleaned engine.  I cover the air
> plate with plastic wrap and
> a rubber band.  I set the spray on the hose for a
> strong tight stream and
> then simply kink the hose for on off while holding
> the nozzle just where I
> need it.  Any tough stuff I spray a second time with
> degreaser and loosen up
> with an old toothbrush or two then hose it down
> again.
> 
> I did a power wash on the V-8 just one time and too
> many gremlins popped up
> as a result of the harsh pressure including the
> rough idle you are now
> experiencing.  All were related to the ignition and
> remedied with new wires.
> Pressure washing can create breaks in old brittle
> wire insulation or tears
> you can see in the silicon plug wires, etc.  I think
> you would be much
> better off in the future with just the garden hose
> and a more accurate
> controlled spray, engine degreaser and a toothbrush.
>  You could follow up
> any wash with your wet/dry vac set up to blow it's
> hot exhaust through your
> vac hose to puddles or damp areas on the engine
> wiring harness etc before
> putting things back together again.  Compressed air,
> if you are equipped,
> works well too.
> 
> Good luck.
> 
> Dick
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "David Fatovic" <coloradocroat at yahoo.com>
> To: "MBCOUPES" <mbcoupes at mbcoupes.com>
> Sent: Wednesday, June 29, 2005 8:11 AM
> Subject: [W126 Coupe] Vacuum problem?
> 
> 
> > I was doing some work on my dads 85 500 SEL last
> > night, and one of the first things I did was power
> > wash the engine.  The valve cover gaskets were so
> old
> > and hard they were letting oil seap out on to the
> > exhaust.  So, steam cleaned the engine, then
> replaced
> > the valve cover gaskets.  Now (actually had
> happened a
> > bit before) under load from about 1400-1900 RPM
> the
> > engine spits and sputters, shimmys and shakes.  I
> have
> > a feeling it is a vacuum problem but not sure
> where to
> > start.  Once you get past about 2K RPM, the engine
> > seems smoother.
> >
> > Any ideas?
> >
> > Also the car in Drive used to idle around 1K-1200
> RPM
> > now it idles at about 650-700 RPM and shakes doing
> so.
> >
> > David
> > The MB Coupes Website!
> > W126 SEC Mailing List
> > Postings remain property of MB Coupes, L.L.C.
> >
> 
> The MB Coupes Website!
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>