MB 250 SE - 66 idle/start problems - Mercedes-Benz Forum

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post #1 of 23 (permalink) Old 06-25-2009, 12:12 PM Thread Starter
p74
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Exclamation MB 250 SE - 66 idle/start problems

I just bought a nice MB 250 SE -66 to have as summer recreation car but it turns out to have problems to start and also runs very bad/not at all when its warm??

Starting when cold is no problem and the car runs proper but as soon as its gets warm the it´s almost impossible to start?

Has anyone had a similar problem?

Would be very grateful for hints...
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post #2 of 23 (permalink) Old 06-26-2009, 01:27 PM
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It would appear that you have a bad warm-up regulator. On the top of your injection pump is a tower with two water hoses coming out of it. Remove the two screws securing the tower, and remove the brass cylinder with the pin on the end. This is the thermostat for the injection pump that progressively leans out the mixture as the engine is running. It is a simple maintainence item. Make sure to replace the gasket as well. Good luck and welcome aboard!

Mark in Spokane, WA, USA
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post #3 of 23 (permalink) Old 06-27-2009, 12:47 PM Thread Starter
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Thanks for the tip! I will replace the thermostat for the injection pump and see what will happen to the idle when the motor gets warm.
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post #4 of 23 (permalink) Old 06-27-2009, 01:45 PM
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Very welcome. A common replacement part, just like your thermostat. BTW, which I would replace as well. They both use the same wax and it is probably ready to bail as well.
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post #5 of 23 (permalink) Old 06-28-2009, 05:09 PM
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Post Thermostat could be jammed

After driving for a while; see if the bottom of the raditor is hot, if hot then the thermostat OK; if not then take thermo out and test it by dipping in boiling water. If the lid moves up and down then thermostat OK if not you may have found the problem.

Let us know how it goes.
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post #6 of 23 (permalink) Old 06-30-2009, 12:49 PM Thread Starter
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I dismantled the thermostat house on the injection pump and it does not look very healthy..
I will try to find a replacement housing.
Is the injection pump/thermostat housing the same as used in the later 280SE >72 since they seem to more common around here?
I attached some pictures of the thermostat housing. I guess there should be a rubber seal instaed of the grey stuff they used to fix the thermostat?
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post #7 of 23 (permalink) Old 06-30-2009, 01:07 PM
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You are correct. It is a rubber o-ring IIRC. Those are an easy find at a boneyard, you definitely need a new one. Yes, they are all the same on the 6-element pumps
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post #8 of 23 (permalink) Old 07-01-2009, 04:50 PM
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Unhappy You need a new one

yup, tht thing is unrepairable. Sure you must have been leaking water - did you notice it?
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post #9 of 23 (permalink) Old 07-02-2009, 04:20 AM Thread Starter
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No that´s the funny thing that it did not leak any water!!
I have had the car in the garage and could not spot any water on the floor but i guess it was just a matter of time before that would happen.
I am now hunting for som spare thermostathousing.
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post #10 of 23 (permalink) Old 07-03-2009, 11:41 PM
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Update?
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