Newb checking some questions about a 75 240d.... - Mercedes-Benz Forum
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post #1 of 2 Old 02-23-2005, 10:58 PM Thread Starter
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Newb checking some questions about a 75 240d....

Hi all, just registered here cause i'm picking up a 1975 240d. I'm a member of VWvortex (vw forums) and i've found online forums invaluable as far as information and advice go...

So here goes, the car is super clean considering its age, with only one minor issues...smoking..imagine that ....basically, here's the information i know, i'm friends with the current owner so he gave me a great rundown...the smoking was pretty bad through all condition so he took it to a local shop (Benz friends, located in seattle)...they told him that the leather diaphragm in the fuel pump was shot after looking at it for a minute or so....they then put a rubber stupper in a vacuum port heading out of the throttle body over to the injection pump on the driver side of the block...this cured alot of the smoking problem, however it still smokes quite bad when you're slowing down via motor compression, and a puff on shifts...

my question is, how hard will that fix be? i've had plenty of wrench time on VW's and audi's...and i'm not scared about jumping into an unknown car, but the whole diesel system makes me want to make sure i know what i'm getting into...the shop also said that there was somthing else that was worthwhile replacing while having the fuel pump pulled, but my friend couldn't remember waht they had said...any ideas on what that may be? and how does this overall diagnosis sound?

thanks very much in advance
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post #2 of 2 Old 02-28-2005, 01:08 PM
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Welcome to the forum!

This is a difficult one. It would likely benefit you to find out just what it is that was blocked off, and check a vacuum diagram for the proper routing of all the other lines.

As for the fear of working on a diesel, don't worry about it! The old benz diesels are as easy if not easier than you vw's and audis to work on.

Now to your smoking problem: Is the car buring motor oil? It sounds as though some fuel is getting in when it shouldn't, or possibly oil. Let's hope that it is not the latter, but a compression check might do you some good. Also check the valve seals.

If it is fuel, then you might have a fouled or faulty injector. Try running some Lubro-Moly Diesel purge through the system (directly, not in the tank) and see if you benefit from that before trying anything else.

It is difficult to say if the mechanic saw something needing to be replaced while he was in there, but there are a number of things that can be serviced on the IP while you are in there including delivery valve seals and the fuel shutoff. I don't really recommend replacement of these until they fail.


\'87 Mer-B 300D (220,000 miles) (sold)
\'93 Mer-B 300D (173,000 miles) (sold)
\'87 Porsche 928 (101,000 miles)
\'98 Dodge Ram quad-cab (250,000 miles)
\'2001 CLK430 Cabrio (50,000 miles)

Past cars: 1969 mercedes 250, 1981 300D, 1972 220D
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