[W126 Coupe] Returning to the Group

[Mister McGoo]

Rob; A couple of questions about your '88 560 not starting after the engine has been running for a while... Does this happen pretty well every time you stop after driving, or just once in a while?  If it is once in a while, is the problem getting more frequent?  Has the engine ever quit while driving and subsequently won't restart?  Have you ever left the car idling for an extended period of time (10-15 minutes) and then had it suddenly quit (and refuse to restart)?  
 
The fault could be the coil although they seem to be pretty reliable.  Or it could be the ignition module itself ($1,800+) but, unlike the pre-86 modules, they seem to rarely go bad.  (Also, in my experience, if the ignition module dies, there's no magic resurrection.)
 
Before you set off, while the engine is still cold, pull the round connector on the upper left of the ignition module (facing the module).  That is the connector for the crankshaft reference mark sensor... the round black wire from that plug should head towards the back of the engine, past the fuse box and disappear behind the engine on the drivers side.  Test the center pole to the ring of the plug on the wire for resistance.  I imagine it will read something like 780-800 ohms.  (I don't know what the actual spec would be).
 
Run the car and subsequently if the engine won't restart after warm again, test the resistance from that sensor again to make sure it still reads the same.  If it still reads the same resistance as cold, you have eliminated that sensor as a possible cause.  If it reads infinite resistance, that is the culprit.  And you're right, it is engine heat that causes the faulty sensor to fail.
 
That sensor (coil) tells the ignition module that the engine is turning and locates the crank position.  If the ignition module gets no signal, it assumes that the engine is no longer turning so it shuts down not only the ignition, but also the fuel pump. 
 
-Bellamy
 
 


Date: Wed, 10 Jan 2007 21:04:54 -0800From: dentrpt9 at yahoo.comTo: mbcoupes at mbcoupes.comSubject: [W126 Coupe] Returning to the Group
Hello all...
 
After a 15 month deployment with the Army to Egypt, I am returning home and have signed back up with this group.  It's great to once again see all the technical know-how this group has, (and I will be tapping into that in a minute), and look forward to learning the ins and outs of W126 ownership.  I have an 88 560SEC that I bought back in April of 2005.  I believe I am the 4th owner and the car has stayed in the Dallas/Ft Worth area until I purchased it and relocated it to Longview, (East Texas, about 60 miles west of Shreveport, LA).  In my opinion, the SEC series has to be one of the best looking cars ever built....although I may be a little partial.
Now to tap into everyone's knowledge.  My car seems to have an attitude.  There are times when it just doesn't want to start.  Not so much out of the blue, but if I take a short drive, kill the car and get out and come back in 5 or 10 minutes and try to crank it up again, it just won't start.  Sounds like it wants to at first, but never quite fires up.  Once this happens, I usually leave it where it is and come back in 4 or 5 hours and the car will fire right up.  
 
So my question is what could be causing this?  Is heat playing a role in it?  Or is there something obvious that I am not thinking about.  Any ideas as to how to track it down and repair it would be appreciated!
Rob Dent
Longview, Texas
88 560SEC


Access over 1 million songs - Yahoo! Music Unlimited.
_________________________________________________________________
Be one of the first to try Windows Live Mail.
http://ideas.live.com/programpage.aspx?versionId=5d21c51a-b161-4314-9b0e-4911fb2b2e6d
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.pairlist.net/pipermail/mbcoupes/attachments/20070112/b92aabf2/attachment.html