Need Mechanics opinion on issue - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 01-16-2009, 09:06 PM Thread Starter
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Date registered: Jan 2009
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Fuel pump or not???

00' ML320

I am a old school jeep guy and have knowledge on old school motor issues but I am helping my nephew on his MB.

Motor running rough, would die on acceleration, idled ok, no power. Not drivable.

Bought a code reader and am getting mixed results occasionally no codes and when I get codes it is P0300, P0301 and last time it was P0300, P0301 and P0303. I understand what the codes say.

Thought coil pack but ruled that out right now. Thought fuel filter removed it, tested pump and saw good flow, and just replaced it.

Car will crank, run a few minutes die. When it died I removed the fuel line going into fuel rail, cranked motor no fuel. Reconnected.

Waited a while until it cranked and ran. Turned it off, removed line going to fuel rail, tried to crank and fuel poured out. Reconneted. Cranked engine, ran for a few minutes and it cut died.

Removed fuel line at rail turned over would no flow.

Repeated the above several times. Basically, if I checked at the fuel line t rail times it was running I would get good flow. If I checked immeadiatley after it died I would get no flow.

As an old school guy, I determine it HAS to be the fuel pump. Is there anything I might be missing that still calls that into question??

EDIT: I removed the fuel line going to the input on the fuel filter. Turn motor over and get no fuel. Fuel pump? The only question I would have is if there is some shut off to the fuel pump from the computer or other sensor? On a '72 CJ5 there is not and the answer is obviously fuel pump..MB ??

sorry for the long post..

Last edited by CJ5; 01-18-2009 at 04:48 PM.
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post #2 of 3 (permalink) Old 03-31-2009, 05:02 AM
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they had a prob with the harness check behind the L/R wheel you should see a connector seperate it and make sure the connections are good
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post #3 of 3 (permalink) Old 03-31-2009, 05:34 AM
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Crankshaft position sensor With no signal from this there is no power to the pump. Sometimes the sensor works and sometimes it fails but on the ML model it will not (always) throw a fault code.


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