I am having intermittent starting problems with my C220. Occasionally it will crank but doesn't start. I am leaning towards a fuel delivery problem.

My questions:
o Once I turn the ignition on prior to cranking should the fuel pump be running? Will it go up to pressure and then turn off?
o What is the purpose of the Fuel Cutoff Relay?

My feeling is that I should be able to tell if the pump is operating by feeling it once the ignition is on.

When you turn the ignition switch on, the pump should run for only a few seconds.

It should run whilst cranking.

Might be best to check this out with two people, one at the switch, the other observing the pump.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Thanks Jim for the quick response. Are you saying that the pump will run until the pressure is built up. What turns it off? Does the Fuel Cutoff relay play a part here?

There is a test port on the fuel rail for checking pressure and flow...

Next time it fails to start, give the OVP a few taps..

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42EB0RZRTB&year=1995&make=MB&model=C-220-001&category=P&part=Overload+Relay

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A Dalton

Can anyone explain to me how the fuel system works? I know there is a FP relay that turns the pump on and there is a Fuel Pressure Regulator that keeps the pressure constant for the injectors. It was mentioned that the pump only stays on for a few seconds when you turn the ignition on and goes back on during cranking and thereafter. I would assume that the Engine Management system tells the pump to turn off after a few seconds. I also assume that the Fuel cutoff valve in not in the loop and is only there for emergencies.

What is your question ?

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A Dalton