1991 190E hard start when warm
 

This unit is new to me, my sister in-law had the car serviced in Vegas and after that it began its hard start when warm deal what could the dealer have gotten out of adjustment to cause this, what happens is it will hit and fire then stall all in just a fraction of a second the next attempt will turn over excessively then try to start and stall, if you let the key stay on for as much as thirty seconds it seam to try to start, if you step on the fuel it just cranks away then it seam to catch slowly then brings itself to a point Ware you can get throttle response. I feel that we are looking at a fuel delivery problem when warm and only on start up when it is running it has great response. JNT :rolleyes:

What work did the dealer do? Why did she take it there?

This sounds like classic a "hot soak" problem, but you did not say how "warm" the car needs to be. If you drive it 10 min and then park and restart is it a problem? Does it have to sit a minimum amount of time to get the problem? For example, if it is hot and you shut of for 10 sec does it start fine or not?

Try to sub the OVP relay and see if it makes a difference.

I admit the symptoms he states seem to indicate the problem you describe. However hot soak (if that is even the condition he is describing) can also cause crank sensors, coils, modules etc to go bad as well. I do not like to throw out suggestions until I feel I clearly understand the specifics of the problem (usually...)....

normal operating temp.
 

once the car is at norm temp of 80 to 90 C and the restart trouble begins, some times if you restart it in 30 seconds or so it restarts just fine but most of the time it will sit for ten or more min. and the hard start shows up.

are you suggesting the center valve in the fuel distributor?
 

I have a 420sel that has the center valve leaking but that just blows black for a second till it clears out then runs fine, but the baby benz turns over trys to start and stalls, the next attempt to start it, it just cranks till it gets the fuel and slowly comes to life, I dont know what service was performed on the car my sister inlaw did not say.

fuel supply
 

I have tried to turn on the key and just let it set for half a min. or so and some times it starts, but not that frequently. I am thinking of looking at the EHA to see what the readings are, the car runs fine and gets 23 city, we use it much more than the big benz, I just wish it had the same ride, but we keep the big dawg for the longer trips.

Well it's a hot soak problem of some kind. If you doubt that then next time it is fully warmed up, park it with the hood up. When you go to start it it will start fine because the heat didn't build up. That will prove it is hot soak. As far as the other symptoms it does sound like the boiling fuel problem that was stated previously. My Supra had the same problem. Basically there was a window between 20 min and 40 min when it would be hard to start. Luckily I usually was parked either less or more than that, or not fully warmed up. I would think other people with the same car would report the same symptom though.