Starting Issue, 1974 280 SE

Carl,
If there is any confusion, it is the the translation Mercedes used for the pump suction damper. They call it a "damper cage". Could have been, say "damper/reservoir" indicating it performs two functions ?? It is there to dampen both pressure fluctuation in suction line as well as reduce pump noise and possible vapour formation. There are many patents on such devices. The one below is used on a kjet and some mercedes diesels. It has a more obvious diaphragm and also includes a fuel return port.
www.ecstuning.com/ES1663654/

Hallo again,

'Dämpfer' ist der Begriff, den Mercedes verwendet. Für mich enthält dieser Begriff aber den Hinweis auf ein technisches Element, das dämpfend wirkt.
Ich erkenne auf dem Bild eine Dose, die mit Hartlot verlötet ist. Die dazu nötigen Temperaturen schließen aus, dass da drin eine Membran verbaut sein kann.

Mercedes kann diesen kleinen Tank (Reservoir, Vorratsbehälter) natürlich nennen wie sie wollen - aber für mich ist ein Tank ein Tank und ein Dämpfer ein Dämpfer.

- Mittlerweile habe ich wohl herausgefunden, warum die Dämpfer teilweise einstellbar sind. Sie sollen ja bestimmte schwingungen mildern, die um einen bestimmten Druckbereich herum auftreten.
Für andere Druckbereiche (z.B. L-Jetronic) brauchen die Dämpfer daher eine andere Grund-Vorspannung.

'Damper' is the term used by Mercedes. For me, however, this term includes the reference to a technical element which has a damping effect.
I recognize in the picture a can that is soldered with hard solder. The necessary temperatures rule out that in there a membrane may be installed.

Mercedes can name this small tank (reservoirs) as they want, of course - but for me, a tank is a tank and a damper is a damper.

- Meanwhile, I have probably figured out why the dampers are partly adjustable. They are supposed to alleviate certain vibrations that occur around a certain pressure level.
For other pressure levels (e.g. L-Jetronic), the dampers therefore need another pretension.

Norbert

Hello Carl888,
I just wonder if the problem is due to the fuel pump losing pressure and then having difficulty self priming. I had starting issues and removed the pump, connected power and dipped the suction hose in a pool of fuel and it took a few goes to get it to suck fuel. Once it did the fuel came gushing out. My fuel pressure drops off readily after the engine is stopped which may suggest that the non return valve isn't working. Also, I once changed the fuel line from the tank to the pump and had a struggle getting the car to start and at the time put that down to the pump struggling to prime itself, as once it was going I had no further issues.. This may be due to wear in the pump.
My car also takes quite a few seconds to start when it has been sitting for a while (longer than an hour), but starts almost instantly if I start it within half an hour of stopping. I may have the same problem, but less severe.
And, rather than set it on fire give it to me!
Regards,
Lance.

So, thinking further, the solution might be to install a non-return valve. There is information on the net from Pierburg showing how they should be plumbed in. Look at the following:
www.pierburg-service.de/ximages/pg_si_0044_de_web.pdf

Hi Lance,

it is correct that Pierburg has these non-return valves that I also recommend in article fuel pump as replacement for broken original ones on the pump. However a broken non-return valve would not prevent a car froms starting. It would just take longer to build up pressure on fuel line but finally it would start.

I fear that Carl has lost his motivation on his car. So we better wait until he has forgotten about his frustration.

Hi,
I once found an alternative part for the Pierburg valve.
Produced by Sytec, made of alloy and brass - not plastic. Price is almost the same.
Search for ' Sytec valve ' at ebay platform.

Regards
Norbert