My car was doing the exact same thing. I ALWAYS had to start it twice when the engine was warm.

I checked the lambda and it was a bit lean. I richened it to just rich of 50%. I went by the duty cycle instead of the EHA current only because I didn't want to bother with the wiring issues and air filter removal.

I have not had it require a restart one single time since. I was amazed and pleased!

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2012 E350
2006 Callaway SC560

Brew, could you tell me how to adjust my engine to that spec..

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2001 Mercedes-Benz C320 3.2
1991 Mercedes-Benz 300E 3.0

Back when these cars were new, fuels did not have oxygenate. Now in CA since about 1996 we have it year round in the range of about one to three percent O2 by mass, with the greatest amount in winter, and many parts of the country have oxygenate, at least during the winter months.

If a KE was setup for 50 percent duty cycle with non-oxygenated fuel, and you then add oxygenate, the system will think the basic setting is a little lean and the duty cycle will increase.

When I checked my car the idle duty cycle was 40-45 percent and 50-55 percent at 2500. This was with winter oxygenated fuel. I've had the occasional starting "problem" when the car is not quite cold in the past, but for whatever reason, it has not been an issue in recent years, and the idle duty cycle is means the basic setting is probably about right for oxygenated fuel - a bit on the rich side, which aids starting.

If you choose to adjust your duty cycle you should know if you have oxygenated fuel or not. If not set the idle duty at about 45-50 percent. If your fuel is oxygenated set it at about 40-45 percent. If you set it at 50 percent with oxygenated fuel, the basic setting will actually be a little lean, and you may have poorer staring qualities.

Duke

Evan, do a search. There's TONS of info to be found.

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2012 E350
2006 Callaway SC560

My '88 260e had a two-time start condition for a long time before I came upon the root of the problem.

I decided to replace the EHA because it had a slight gasoline leak that I was afraid would get worse. After replacing the EHA, the car starts on the first turn of the key.

I believe the slight leak allowed the residual fuel pressure to drop enough to cause the fuel to vaporize causing "vapor lock" under certain conditions with the engine warm and propably also required more time to build up pressure again when cold starting the engine.

My advice, in addition to setting the EHA duty cycle or current to spec's. is to remove the air cleaner after the car has been driven and sniffing around the back side of the fuel distibutor for a leaking EHA. The EHA is a little rectangular black box bolted to the rear of the throttle bodyt with two wires going to it.