MERCEDES 190E OVER-FUELING PROBLEM CAUSING NON-STARTING - HELP PLEASE!!

I have a mercedes 190E 2.0L Auto (1990 model) which was runnning beautifully until it refused to start 4 weeks ago with absolutely no previous symptoms. the car did not even try to start i.e not even a
cough or splutter. At first I cheked the usual suspects:
Ignition system - nice fat blue spark found at ech cylinder, new distributor cap fitted just in case, new rotor arm fitted, new spark plugs fitted, new air filter fitted - all functioning fine - all fuses cheked, all fine
Fuel System - blockage cleared in fuel distributor by dismanteling and rebuilding it, new fuel filter fitted, fuel pump and fuel pump relay checked and working fine - fuel at inlet to distributor was fine at high pressure, and a nice fine spray was emmited at each injector
However, none of these replaced parts solved the problem. Today however I narrowed down the problem to that of overfueling. The spark plugs are being saturated with fuel and are therefore not sparking atall. I came to this conclusion after I dried out the cylinders (by leaving plugs out for a week), and dried out the plugs too. I span the engine with no plugs in to clear any fuel in the cylinders and then replced plugs and tried to start the car with NO fuel pump relay. The car fired and ran rough for a few seconds and then cut out (probably due to lack of fuel as pump was not running), but at least it proved the car still runs. when the pump was replaced the car would try to start for about 10 seconds but not quite manage it, and then the plugs would become saturated and the car would not start atall until everything dried out again.
Another test I carried out was to crimp the fuel inlet line to restrice the flow of fuel to the engine, as well as un-attatching the cold start electrical connector. doing this I managed to get the engine running for a couple of minutes, but as soon as the crimp was released the engine cut out again, thus proving the problem to be fuel over-supply.
I think have narrowed the problem down to three possible causes:
1. Faulty fuel distributor 2. Faulty fuel pressure regulator (the part that sends unused fuel back to the tank - if not working correctly all fuel goes into engine and none back to the tank) 3. Faulty cold start valve (and/or temperature sensor) causing too much fuel to be permanently injected into the engine.
If anyone has had this problem before I would be grateful of some help in pointing me towards which of the three (or indeed any other possible causes) is causing the problem.
Thanks
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Good investigation and pursuit of the leads!
Suggest you focus on the fuel pressure regulator. It's a spring loaded valve which also has a intake manifold vacuum connection. If you remove that vacuum hose from the fuel pressure regulator and fuel drips from the regulator the cause has been found. Install a new regulator. Done. I suspect fuel is leaking into the intake manifold through the vacuum hose connected to the fuel pressure regulator, accounting for all the spark plugs' wetness.
Otherwise, it on to the cold start valve which may be stuck open, an unlikely possibility, in my opinion. Its electrical chain typically produces no current to the valve when those parts fail so cold starting is difficult, but hot starting is OK.
Good luck with it.
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Sounds like the problem I chased for months:
My best guess is a defective EHA (Electro Hydraulic Actuator), which is the small black thing with an electrical lead to it, fitted on the backside of the fuel distributor.
Unfortunately, it costs around 400$, and there is no other way (that I know of) to exclude it other than replacing it. And you have done all other things to exclude other parts.
The fuel distributor itself will mechanically adjust the mixture (pressure to the injectors) according to the air mass measured by the plate. The mixture at idle can be adjusted by screw, which is protected by a plastic plug. I assume, that you have not tried to adjust it(don't try). Next, the mixture is fine adjusted by the EHA according to the ECU's calculations based on inputs from mainly the oxygen sensor.
Of course, it could also be the ECU telling the EHA to open wide. Try to disconnect the plug from the EHA and see if it will start then. If it still won't, I suggest you replace the EHA.
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