e250 Diesel 1995 (non turbo)

team45

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Oct 22, 2007
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Hi Everybody,

After changing the fuel filter, I had a problem with the adjustment knob on top of the fuel filter on e250 diesel 1995 ( non Turbo). When I closed the adjustment knob clockwise the car loses power, very diffult to drive but the engine still runs. However if I loosen the adj knob a little bit, the car drives normal but consumes alot of fuel.

I would like to know what is the function of the adjustment knob and what the correct setting should be.

Thanking you in advance.
 
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team45

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Oct 22, 2007
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I would like to know what is the function of the adjustment knob and what the correct setting should be.

Many thanks
 

SilverSaloon

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Mar 16, 2004
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1994 W124 E300D Estate, 1985 R107 280SL
as nick says is the fuel shut off. turn it as much as you can anti-clockwise (unscrew), but not tight as it can damage the valve.... and leave it there, otherwise the fuel will not flow correctly. there is no adjustment on it..... if the car is using more fuel than expected, check the timing maybe? what do you consider high fuel consumtion? these old diesels are not very fuel efficient.....
 
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team45

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Thank you very much for your helpfull reply SilverSaloon,

I am only comparing fuel economy with before I service the car. It just seems to me car is spending more fuel after servicing the car and lost pulling power. I didn't know where this nobe should stay I left it loose (unticlockwise) and noticed no power and I tried to thigten it (clockwise) and same stall and no power only if release it little bit from thigten (clockwise) position I get reasonable performance. But car was better before replacing the fuel filter. I asked my local garage who replace the fuel filter he told me that this nobe should stay thigtened (clockwise). I think he doesn't know what he is talking about.

Many thanks.
 

SilverSaloon

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1994 W124 E300D Estate, 1985 R107 280SL
yeah - try a different mechanic!!! it even has an arrow ontop of it that says "STOP". (clockwise!)

anyway, i think you have an airleak. are there any bubbles in the clear (yellow) plastic fuel lines around that area?

if so, you need to replace the oring seals. the mechanic should of also replaced the smaller oring on the shut of valve bolt aswell when he did the filter.

the valve itself can leak.... but i suspect there is air getting in the system since its been disturbed, especially if the mechanic doesnt understand the system.

tightening the bolt does nothing but block the fuel line, undoing the bolt simply makes the hole that runs in it in the right position to allow fuel to flow though.
 
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team45

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Oct 22, 2007
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Hi SilverSaloon,

Yesterday I unscrew this valve until the end as you advised and draw the car couple of hours. When I inspected after driving I saw lots of fuel leak around this valve and fuel filter was completly wet because of this leak. Do you think my mechanic forgot to put some part after replacing the fuel filter. By the way there is no air bubles in those clear fuel lines.

Many thanks.
 

SilverSaloon

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Mar 16, 2004
Messages
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Car
1994 W124 E300D Estate, 1985 R107 280SL
i'm surprised you have no bubbles in the clear pipes with a leak at the valve, but maybe its not enough.

try tightening the filter bolt a bit more.

try undoing the bolt and unscrewing the filter, keeping it upright. then remove the valve bolt and check there is an oring on it.

then tighten it up and see how it goes.
 

Number_Cruncher

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Jan 14, 2008
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Location
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Car
1995 E300D
i'm surprised you have no bubbles in the clear pipes with a leak at the valve, but maybe its not enough.

try tightening the filter bolt a bit more.

try undoing the bolt and unscrewing the filter, keeping it upright. then remove the valve bolt and check there is an oring on it.

then tighten it up and see how it goes.
The secondary filter is on the pressure side of the lift pump rather than on the suction side, so, I would expect leakage rather than drawing air.

DON'T over-tighten the filter bolt - it will achieve nothing but damage.

As Nick suggested, make sure the 2 O rings are OK and in place on the outside of the bolt.

If necessary, the filter / stop bolt can be disassembled, and the tiny O rings inside the tap renewed.

As has been mentioned, the valve is a stop valve, and usually should be simply left open - fiddling about with it will only cause leaks - sorry!, you know that now!
 

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