Sudden Engine cut-off, 1970 280 SL Automatic

[signalred280sl]

While adjusting the settings of the venturi control unit vacuum governor according to the instructions in the Haynes manual , with the engine having been on idle for maybe fifteen minutes total time, with several ons and offs, the engine suddenly cut off and would not re-start. The engine would turn over but apparently no spark. After about ten minutes and several tries, I heard a "click" in the engine compartment. I rushed to try to start it again and magically it started fine. This has happened to me twice in traffic before - very dangerous - embarrasing - etc. Can anyone tell me precisely where the relay, temperature switch, solenoid , or whatever, is that causes this to happen. Certainly there is a way to bypass the culprit long enough to get you off the road until the engine cools down or whatever it does that allows it to restart. If you have the circuit diagram involved I would appreciate your sharing it with me and any other information that will help with this problem.
Thanks,
Les

[Tom]

Les,

Just a guess, but try taking the wire off the deceleration solenoid at the back of the Fuel Injection pump.  Sudden fuel cut-off in traffic may be linked to the decel solenoid.  Your model year should have just one solenoid on the back of the FI pump, which was related to emissions (I think).

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1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
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[signalred280sl]

Tom,
Thanks for the input. Removing the wire from that solenoid was the first thing I tried when the engine shut off but with that wire disconnected, the engine still would not start. Once before when that happened I was not able to get a spark from the ignition, seeming to indicate that the temporary refusal of the car to run was due to the ignition system being interrupted for some reason.
Les

[hands_aus]

Anything to do with the adavnce / retard springs in the distributor?

Did it cut off at idle or were you revving the engine a bit?

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[signalred280sl]

Bob:
It cut off while at idle. I tried to repeat the situation this weekend but was unable to get it to cut off this time but I did notice that the "click" noise I had heard the time before was probably just a contraction of the exhaust as it cooled off a bit rather than a solenoid or thermo switch. I'll check the distributor and make sure the advance mechanism has a little oil on it.
Thanks,
Les

[n/a]

Here is another scenario to consider:
I have a 71 280 SL with factory electronic ignition. It always started quickly and generally ran smoothly until it warmed up. Then the engine sometimes ran rough; also died at idle at stop lights, etc. It always started up quickly again. One day after I put it in the garage it refused to start again (no spark.) I had to correct the problem by replacing the electronic control unit and the condenser (just in case). Now the car runs better than every before and so far I have not had any problem with rough running or dying at idle.

The company that rebuilt the electronic control unit also offers a bench test of your unit before you buy another, if you want to find out if that is the problem.

details at www.programainc.com