[W126 Coupe] Hard start

[Dick Spellman]

Hi Hovsep:

With engine off maybe check a few of these basic items that can and do 
cause hard starts:

   1. Pull a couple of the new spark plugs to see if any are oil soaked
      or fouled - worn valve seals and/or guides allowing oil to seep by
      when engine is off.
   2. With a flashlight and your hand gently depress the air volume
      meter plate all the way down and look towards the pivot point to
      see if it's dry (dull black) or if it becomes shiny wet in
      appearance after a few seconds - wet suggests the fuel distributor
      rubber control piston o-ring needs replacement.  This will cause a
      hard start and you would also smell fuel from the excess in there
      from sitting.  Another sign of a fuel leak somewhere (injector or
      control piston) is having to depress the accelerator to allow more
      air while you crank the engine until it starts and burns off the
      excess fuel before smoothing out again it will smell of gas from
      running rich.
   3. Test the throttle plate switch for fully closed by reading with a
      simple ohm meter - not closed suggests carbon has fouled the two
      pivot points and it needs to be cleaned ( I had to pull my
      throttle body and tank it to clean then replace the gasket when
      done - it was not possible to clean it so the plate closed as it
      should while on the intake manifold, too dirty from many years of
      neglect) Be sure and check the manual for the correct (2) pins on
      the 3 pin plug to do this test.

I've had the hard start, the stumble, the stall when coming to a stop, 
the low idle, the persistent miss at idle, the smell of gas when you hot 
start on every M103 engine I've run.   The good news is the fuel and 
engine management systems are fairly similar between M103 and the V-8's 
in the SEC's.  I have at one time or another had to go over every item I 
just detailed to eradicate and repair only those items that had failed.  
So, plugs, caps, rotors, wires, cracked vacuum lines in a number of 
places, o-rings, injectors, control piston seals, throttle body work and 
more.  Just takes time and a plan to figure out how many different 
things are wrong.  You may well fix one only to find another.

Good luck,

Dick

Hovsep Dovlatian wrote:

> My car has been having a problem with hard starting. Ive checked the 

> fuel presure and its there. Ive checked the spark and the wires 

> they're all good. So I just wanted to know is there anythiong else I 

> should check???

>

> Thank You,

> Hovsep

>

> ------------------------------------------------------------------------

> Check out the all-new Yahoo! Mail beta 

> <http://us.rd.yahoo.com/evt=43257/*http://advision.webevents.yahoo.com/mailbeta> 

> - Fire up a more powerful email and get things done faster.

> ------------------------------------------------------------------------

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.pairlist.net/pipermail/mbcoupes/attachments/20061113/ac21c698/attachment.html