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1996 E300D fuel leak

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zak
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Bernardsville, NJ
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Joined: January 26th, 1994

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1014

Vehicles
2002 G500
1999 E300 Turbo Diesel
1987 300TDT
1967 250SL

I was smelling fuel around the car for the last few weeks. But I thought I would deal with it at next oil change- in about 1000 miles. But last week I go to leave in the morning and the engine won't start. It cranks fine. I know glow plugs are new and in order. It almost started a few times , but wouldn't. It seemed that it was starved for fuel.
I had the car towed to my MB dealer and their diagnosis was that there was a leak at the fuel shut off valve and pressure was bleeding off. 3 other leaky fuel lines were also replaced.
The car now runs better than ever. The engine seems a bit more responsive. Just prior I was feeling a bit of a lag during hard acceleration.
I checked under the car a few times for drip spots when I started smelling the fuel and never saw a drop on the ground. So how could a leaky fuel shut off valve leak so much as to render the engine unstartable and show nothing on the ground?
Something doesn't sound right. But the car is now running like a champ.
Any insight would be appreciated.

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Anonymous
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I am going to check that on my car, also a '96 E300D. When the tank is below 1/4 full it will not start without lots of cranking if it is parked on any kind of an uphill incline. I have mentioned to my mechanic that I feel like the fuel is running back into the tank and he did not believe me. I am going to mention the fuel shutoff valve, see if I can get it checked.

zak
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zak's picture
Bernardsville, NJ
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Joined: January 26th, 1994

Posts:
1014

Vehicles
2002 G500
1999 E300 Turbo Diesel
1987 300TDT
1967 250SL

Thanks Marshall, you gave me what I wanted. A reasonable answer that I can understand. And within 2 minutes of my post....
Do you think that the leaky valve was negatively affecting engine performance? Would it possibly affect MPG's , as well ?

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nhdoc (not verified)
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Don't let appearances fool you...

Your car has a "belly pan" which cleverly catches most drips and holds them, at least until you drive away and centripetal acceleration and wind disperse them. Unless you have a constant leak or one which is very severe you would not see a puddle under the car. That's why you smelled it but may not have seen any drips. When you shut the car down and the fuel in the lines leaks out it takes quite a bit of cranking to re-prime it to start again. Your car would have eventually started but you would have to crank it much longer than normal to get there...so what you did was the right thing...if you smell diesel, have the leaks fixed!

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Hold a light behind the clear plastic fuel lines and check for air bubbles. Since the engine driven fuel pump "sucks" fuel forward from the tank, it will also pull in air if the line seals are compromised. Sometimes you get a fuel leak and sometimes you don't. Replace the plastic lines and use a dab of silicone on the seals before you install. Also check the electric fuel shut-off for leakage.

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sur5er wrote:
Hold a light behind the clear plastic fuel lines and check for air bubbles. Since the engine driven fuel pump "sucks" fuel forward from the tank, it will also pull in air if the line seals are compromised. Sometimes you get a fuel leak and sometimes you don't. Replace the plastic lines and use a dab of silicone on the seals before you install. Also check the electric fuel shut-off for leakage.

That would be silicone LUBRICANT :D

zak
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Bernardsville, NJ
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Joined: January 26th, 1994

Posts:
1014

Vehicles
2002 G500
1999 E300 Turbo Diesel
1987 300TDT
1967 250SL

Thanks Dick. I will have my trusty flash light out this saturday.

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nhdoc (not verified)
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The only line you should see a bubble in is the one which feeds the pre-filter. On every one of these cars I have seen a small bubble develops there after shutdown and it is apparently normal. If you see more than just a small bubble there or air anyplace else in the lines then you probably have a leak.

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