Injection pump starting solenoid.

[Paul99]

My starting issue is driving me nuts now.  Starts cold perfect. Turn off the car. Hot or cold. Will not restart. There is a spark. Fuel. Wrd working perfectly. But won't start unless you leave it for a couple of hours then perfect.

If it were a modern car I would say it's the electronic security system cut off.  Which it doesn't have!

So could the starting solenoid on the injection pump do that ?  Can't find much about it in the starting aid tour.

[Peter]

First thing I would do id the tests as described in:
https://www.sl113.org/wiki/Restricted/Engine-starting-aid-tour

[Bshaunessy]

I’m having the same hot NO start issue.  Seems to be a pretty common problem.   Also seems to be related usually to the Thermo time switch and cold start valve system.
   I am waiting on a replacement Thermo time switch but in the mean time, I have grounded ( via a temporary under dash switch) the "W" terminal on the TTS.
   This work around is covered in the Tech Manual / starting aid tour.
  The net effect is that the Cold Start Valve ( CSV) injects fuel whenever the engine is cranking.  Sometimes on hot start you only want one or two seconds of CSV fuel…..as controlled by the temporary under dash switch.
   Anyway, using this hoky and manual system , I can now get my car to hot start.
   It’s taken a few tows home to get this sorted out!

   

[Paul99]

that's the problem. All tests work.  Fuel injecting into manifold when cranking (have grounded the W connection so Fuel injects weather hot or cold) ,  fuel pump pumping,  Spark at the plugs. 

Starts fine cold.  Even after 2 mins running, wont restart, even when engine is still cold.  Literally like spark/coil disconnected, yet plugs show a spark.

[rwmastel]

Any work done or changes made before this problem crept up?  Did this problem start to happened occasionally, got worse, and now happens consistently?  Or, did it just start happening consistently out of the blue?

[Paul99]

Well it was always a bit of a pain to start hot but I think they all seem to do that.  It has only just started to really be a problem so something has just happened- or just a few issues have mounted up and its the final straw. Can did run well, doesn't burn oil etc.

Now clutching at straws... 2 suggestions are : 1- The fuel injection solenoid on the Injection pump, (mine is an early 230) and 2- valve clearances when hot could be compression is a bit low so will check those.

Otherwise baffled.

[rwmastel]

1- The fuel injection solenoid on the Injection pump, (mine is an early 230) and 2- valve clearances when hot could be compression is a bit low so will check those.  Otherwise baffled.

Well, when my 230SL was running years ago, it had LOW compression.  Never had a hot start problem.  But, regarding being "baffled", all I can say is to set as many things as you can to a Known Good State and work from there with facts learned from testing.  A lot of people will hear your symptoms and say "this thing is bad, replace it" or similar.  Don't fall for that.  Test, get facts, follow the facts.  Yes, a lot of these systems have multiple components, or some systems depend on other systems to be working to have a good outcome, and it can get complicated or confusing.  Just understand the systems as best you can, set right what you can set right (for free or for little cost), and think it through.  Try to keep all the troubleshooting and updates in one thread so others can get the whole picture.

[Paul99]

So the latest is I removed the wires from the fuel injection pump solenoid and now the car starts perfectly.  It seems (as suggested) that solenoid was allowing too much fuel in and flooding the car during starting. Without it it starts fine so I will leave it disconnected.  Clearly the system which activates that solenoid has gone haywire and will try to work out how or why.

[wwheeler]

I disconnected my starting solenoid years ago because of issues starting when hot. I think it was too much fuel as well. Once I disconnected it, it start wonderfully hot. The only issue is when cold, it needs a bit more fuel. I installed a cabin switch to the CSV. I give that a push for a second or so before cranking, and engine fires right up when cold.

The CSV cabin switch s a common fix.