1991 2.3ltr 190E wont start

Hi, I am having problems with 1991 190 2.3ltr Merc. Wont start. Fires up with squirt os start fluid so will presume ignition is OK. Fuel flow checks out OK. Pressure at delivery to distributor valve goes off
scale on guage (140 psi) when key is turned on then drops back to 40psi and stays there. When cranking engine the pressure goes off scale again (140psi) Fuel at cold start injector but nothing from the distributor valve to the injectors.Have checked the 2 overload fuses OK. Can anybody help please ?
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Fuel pressure is too high... Most likely pressure regulator is bad.
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Check the fuel return-to-tank line. I saw one that was nearly plugged off with rust. If fuel will not flow back to the tank, the pressure regulation will not work.

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Thanks for your replys guys. Will check your help on monday. I think I am taking my reading from the fuel line before it gets to the pressure regulator. I have since read that pressure is taken from a capped port on the distributor body, not directly from the supply inlet. Will try this and see if regulator is faulty. Thanks again. Will let you know the outcome !!
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Today I checked out the pressure regulator and it is fine, running at 75psi when cranking. Left guage connected to the test port in the distributor head,put some gas down the inlet and it fired up and kept running but only above 2500 rpm.. Bled the injectors while it was running at these revs and it ran quite smoothly. Pressure guage still showing round 75psi. Below 2500rpm the engine will die but fuel pressure remains the same. When cranking again, no fuel is coming from the distributor hesd but pressure is good. The distributor valve only seems to work above 2500rpm. Removed dist head and checked that it wasn't sticking and it moves freely. Any ideas. Would appreciate any help.
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Did you replace the EHA valve? That black box on the fuel distributor?
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Reach under the intake manifold from the front. Feel for the U hose that connects from the middle of the manifold and goes back to the bottom of the idle stabilizer. When one end of it pops off...... you get the same symtoms you have.

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Thanks Karl, you were dead right. An old guy who dismantles Mercedes told me to go there and that was what had happened. Apparently if you get a kickback into the inlet manifold it often pops this pipe off. Has no clamps on it and stops damage to the air valve plate. The so called merc experts were no help at all. I appreciate everyones help ! Thanks, Ken.
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