R-Class (W251) Produced 2006-2013: R320CDI, R350, R420CDI, R500

R320 fuel leak and dead bettery

Old 02-15-2016, 06:59 PM
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2008 R320 4MATIC
R320 fuel leak and dead bettery

So I have noticed an odor of diesel fuel at night in the garage. The car runs fine otherwise. Been meaning to get around to it I have just been busy. I removed the engine cover and can see fuel on top of a small canister on top of the engine.

Recently standing in the garage I noticed a high pitched sound like the fuel pump running, an hour after I turned it off. My wife even said she heard it at 10 o'clock at night, I'm home by 530 or 6.

I just replaced the battery a few months ago and now it seems to be dead again.

So my question:
Does the R320 fuel pump try to maintain fuel pressure even when the car is off?
Thanks
Old 02-15-2016, 07:24 PM
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2008 R320 CDI, 1987 560SL
It shouldn't. I noticed an odour also, and observed black residue around injector 1 indicating a seal failure, which I am currently working on. I'll report back.
Old 02-15-2016, 09:46 PM
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Originally Posted by marc hanna
It shouldn't. I noticed an odour also, and observed black residue around injector 1 indicating a seal failure, which I am currently working on. I'll report back.
Yours may be leaking slower than mine. I can see a good bit of fuel on tip of the little round cannister on top of my motor.
Old 02-15-2016, 10:20 PM
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You may need to replace an injector. Part #A6420701387

Shop around for a price. You should be able to find them for under $200 USD.
Old 02-19-2016, 05:28 PM
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Shop says it's a leaky fitting on the fuel filter housing.

My dead/fried battery is due to a faulty rear SAM module which is trying to power up various components while the car is off. This explains the apparent fuel pump cycling while it's off.

Just so happens that it contributes to the damn fuel leak that makes the air in my garage toxic!
Old 01-25-2017, 08:05 PM
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So I got all these things in the last post fixed shortly after afterward. Now it's got another fuel leak. The aforementioned repaired fuel filter housing is dry. I can smell fuel again in the garage at night. Here's the new slightly disturbing symptom; I can see a very fine mist of fuel at night passing through the headlights. I got close and the mist definitely smells like diesel. I wonder if it could be coming out around an injector or from the high pressure pump somewhere?

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