1971 220 with Weber Carb Fuel Flow Direction

tompat42

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I am installing a Purolator F21124 in-line fuel filter WITH NO direction arrow to show fuel flow direction. Does fuel flow from the tank (via a push electric fuel pump mounted at the tank) into the fuel filter end with the element, thru the element and then into the fuel filter cavity and to the carb or vice versa? Newbie to site so bear with me if I am not creating this thread properly.
 
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Number_Cruncher

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Your Mercedes
1995 W124 E300D TE
I would expect the fuel should flow in the direction which tends to push the pleats of the filter out against the inner surface of the filter housing rather than the flow pushing the filter in on itself, leading to collapse.
 
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tompat42

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That is the way I have it mounted. I noticed that when I shut off the engine, fuel flows from the carb side back thru the filter until it is empty. Is this normal? There is not a fuel return line for the Weber as was the case with the original Stromberg. I am trying solve what appears to be a fuel starvation problem. Fuel pump checks out ok. Engine starts and idles fine but spits and sputtersnunder load and acceleration. Plugs, ignition, wires, coil are all new and timing is set properly. Any ideas?
 

Number_Cruncher

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Your Mercedes
1995 W124 E300D TE
What pressure is your fuel system running at?

I ask because it will be easy for an electric fuel pump to create enough pressure to overcome the float valve in the carb - especially if the system was originally designed to work with a fuel return system.

It's a broad brush figure, but, I would become wary if there's much more [or less!] than 4 psi of fuel pressure at the carb when the fuel pump is running.

The fuel running back might indicate that the one way valves in the fuel pump aren't sealing properly - they may be being held open by grit, or maybe worn out?
 


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