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Old 08-19-2014, 09:24 PM
outofspec outofspec is offline
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Join Date: May 2006
Location: Hudson WI
Posts: 178
1999 ML320 Substantial Fuel Leak

Hello ,

On a recent trip my 1999 ML320 developed a major fuel leak in the rear of the car. The leak is only apparent when the car is running and shortly thereafter. It completely stops, apparently after fuel pressure is bled down.
I took out the drivers side wheel well, to expose the fuel filter and the fuel lines. I also took out the rear seat and lifted the carper to expose the top of the fuel tank and the hose connections. All appeared dry and not leaking. I started the car and there was again, a massive fuel leak. It was hard to trace the origin and appeared to be running down the tank from the area of the filler neck inlet. I question whether it is possible for the filler neck to only leak with the car running and the system under pressure. Additionally, I cant find the end of the small fuel line that runs from the fuel filter to somewhere on top of the tank in the area of the spare tire carrier. I see there are two large lines that run from the filter to the tank, as well as one large line that appears to run to the front of the car. Then there is a small, low pressure mystery line that comes off the filter to an unknown point over the fuel tank.
I replaced the fuel filter with an updated version and lines about 5 years ago without incident. Vehicle has been running fine to this point.
Any ideas? Does the mystery line go to a vent or canister that s clogged? Could the fuel filler neck be defective?

Thanks for your kind attention.
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