Thanks Guys! Let me tell you a little bit more of what I have done so far. I have replaced all rubber lines both feed and return. This is the good Part! I have pretty much eliminated the tank and fuel lines as the immediate cause by building and installing with primary attached..(under the hood!..lol) an auxiliary 6ltr gas can therefore bypassing that part of the system completely temporarily of course! and still experience the same issue. This issue must be from the primary and beyond. It's a tricky one for sure! Primer pump is of the new type (Black metal head)

the car! 1984 Mercedes-Benz 300D

The newer hand primers are covered with Black Rubber.


There is some aftermarket companies like Flag that make the old style hand primers with the same hard plastic knob but it is black instead of being white. So a white knob is not always an indicator of a new style Hand Primer.


A long time ago one of our members had an issues with several of the new style genuine Bosch hand primers he got from the same store. He finally got his money back and decided that that particular store must have got a bad bunch of Bosch pumps.


He went to another one of the same companies stores and got what turned out to be a good one from there.


There is also copies of the real Bosch new type hand primer. Some by other legit companies and some may be fake.


The pic is of a new style Bosch however the part number on it may not be for a Mercedes.

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84 300D, 82 Volvo 244Gl Diesel

The one that is installed now on my vehicle is the one you are showing in the pic. Definitely a good and inexpensive place to start.. Thanks!