i have a problem with ml320 loosing fuel presure
fitted new pump, filter.
not loosing power to pump
no codes come up in scanner

If you connect a guage & the pressure drops immediately after shutting of the engine then either 1 of the parts are defective OR 1 of the injectors must be leaking.

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MERCEDES Benz Master Guild Technician (6 TIMES)
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Retired Moderator

In ML320, does the fuel rail get pressurized in key position 2 (ignition) or key position 3 (start)?

Mine doesnt get pressurized till it starts cranking and the engine usually starts on a second try.
I swapped the relays around but no joy so far.
The problem is exactly like the one described here: http://www.peachparts.com/shopforum/showthread.php?t=225790&highlight=fuel+rail+presure

Anyone knows?

Your fuel system should still be pressurized from the last time you ran it. Probably the check valve in the fuel filter is bad, mine was. Replacing the fuel filter fixed it.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C