I am under the assumption that you should only use MB formed low pressure hoses, is this correct or can I go to a parts store and purchase low pressure plastic hose and still be safe?
Right now can't get the 220D started, put new pump in and changed hoses, still can't bleed all air out. Bubbles stay in lines without moving. Only if I open small set screw in injector pump do the air bubbles move, but they move in the wrong direction. They move back towards the main fuel filter. Any suggestions would help,(is this a sign that there is still a leak?)
Thanks

Are you talking about the 3.2 mm leak-off lines between the injectors or larger supply lines from the pump? The leak-off lines flow back to the return side of the fuel filter housing...so your bubbles may be going in the right direction...if I understand the question.
Regards,
Randy D.

I was talking about the larger supply lines. I put clear lines on and now I can see an air bubble that does not move. This bubble is located just before the injector pump. It neither moves when the hand pump is actuated, nor when you turn the vehicle over.
Is the injector pump drawing fuel in? If it is can you monitor the draw?
Thanks
Joseph

Hi Joseph,
It sounds like there is either a cracked line or the supply pump (the part the hand pump screws into) is bad. You can check the supply pump with a vacuum gauge while cranking the engine to see if it's working.Yhe supply pump is available as a separate piece.
Regards,
Randy D.

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W.R.Durrance
ASE Master Tech
Mercedes Tech 21 Years
68 250SE
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5
81 300TDT
W.R.Durrance Engineering

You were right Randy, Fix the leak now have good pressure up to number one injector. But the sad part is number 2,3,4, are all dry. I've pumped so much that I can feel the hand pump getting very hard to pump.
Is there a problem with the injector pump?
How can I test it?
Glow plugs are new, I have a bad relay?
Thanks for the help, greatly appreciate this forum and its members helping me to get this started.
Joseph

Joseph,
Are you opening the venting screw on the main filter so the air (and some fuel)can escape from the system while you are using the hand pump?

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Ted
1979 240D
160,000 miles

Yes I opened the vent to bleed the system.

Might you have a blockage in the flex hose between no. 1 and no. 2 injectors? Perhaps the safest thing would be to replace these lengths of hose between the injectors. Also, don't forget to replace the plug at the end of no. 4 injector.

Replaced all hoses in system, except for the steel lines. Replaced all filters. Today fuel came out of number two line, but not number 3 or 4. Glow plugs have battery voltage, but not sure they are turning on. Does anyone know where the relay is on a 73 220D? Thanks so much for the help, I think I am almost there with starting it.
Joseph

You may have improperly installed one or two of the fuel valves. A fuel relief valve should be installed on the injection pump's fuel return circuit. This is located on the pump side close to the engine block, and near the front.

Next, an air bleed valve (with an orifice) should also be installed on your fuel filter's return fuel circuit.

Have you checked your in-tank strainer and fuel pre-filter (nearest the feed pump) for blockage?

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Jake

I not sure what a fuel valve is? I replaced most lines. Now that I think of it there were lines that went to the side of injector pump that I did not change. Could they be blocked inside.
That is the second time I was told to check fuel pump and I haven't, That will be checked tomorrow.
Thanks
Joseph
Glow plug relay? Location

Opened the system up to check pump. Results, approx. 4" of vaccum at inlet. Outlet the highest on gauge was 5 and that was immediately pegged. So I am figuring the pump is good. I want to check to see if the lines are clogged at tank. Although one of the operations I did prior to all this was to drain tank contents. Would the tank operations cleared the lines of unwanted materials?