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Old 06-29-2008, 07:12 PM
MB Diesel Nerd Trainee
Join Date: Oct 2007
Location: Salem, Oregon
Posts: 75
Fuel leak, but not from lines (as far as I could see)

A few days ago during a hot day, my car got hotter than normal when sitting in traffic. However once I got rolling and air flowed through it cooled off- this repeated several times through rush hour traffic. Later on I took a drive out of town to work, and noticed my fuel gauge was going down down down but thankfully made it there.

I took a look, thinking a return line bursted or one of my halfway done wvo setup lines had disconnected, but everything was intact. I checked under the car, and the fuel was leaking from out the oil pan ... an odd place in my mind.

Only today did I begin to think that the heat cracked something, and the fuel is leaking from the engine. Is this likely? The temp didn't get all the way to the 120C mark, but uncomfortably close. Hell, anywhere past 80 or 90ish would make me cringe. But I'm guessing it got to 100C...

Either way I look at it, even if the heat didn't ruin anything, I still have no idea where the fuel could be leaking from. It was still dripping out steadily, minutes after the car was shut off. Let me know what you think, I believe no matter what I'm taking it in to a local Benz shop because this is beyond my scope.

Thank you,

1981 300SD, odometer stopped at 188,000
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Old 06-29-2008, 08:49 PM
Diesel911's Avatar
Registered User
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 30,901
Check your oil level to see if it is high and see if it is diluted with fuel.
The only place that I can think of that could get fuel into the engine are a Fuel Supply Pump (O-ring on the pin that pushes the pump piston), internal leaking of IP where the Elements are (plunger and barrel assemblies). (Did you recently change the Delivery Valve Holder O-rings?). Lastly if an Injecto Nozzle Pintel was stuck open and pouring raw fuel into the cylinder (but you would have a really bad miss if this was happening).

For the falling fuel gauge; if you have 2 tanks maybe the fuel is going into the tank without the fuel gauge. Another possibilty is the Fuel Tank Sending unit is shot or you have an electrical circuit problem between the fuel gauge and the sending unit.

If your lube oil level is not high and there is no fuel contamination in the lube oil you have an external leak somewhere.
84 300D, 82 Volvo 244Gl Diesel
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Old 06-29-2008, 09:01 PM
Registered Hack
Join Date: Mar 2008
Posts: 4,625
Does it take a few cranks before start-up? This might help where the leak is coming from, such as a pressurized source indicated by the leaking after shutoff.

If it takes a few cranks or runs rough at first then pressure is is being restored in the fuel system.

I have no good suggestions except to trace the leak after cleaning the area


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