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Dually Club #3
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Discussion Starter #1
I have developed a raw fuel smell when sitting at stop lights, or slower speeds in town. The smell dissipates at highway speeds. I have looked high and low for a fuel leak and have not been able to find one. My fuel mileage has also dropped about 2 mpg for the last two tank fill ups. Has anyone had this issue, know where to look?
 

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I would guess you are smelling exhaust and have a cracked Y pipe at one of the flex joints. You will lose some boost with a cracked pipe too affecting mileage. I would think you'd see drips on the pavement if you were leaking fuel.
 

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Dually Club #3
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Discussion Starter #3
The smell I am getting is not an exhaust smell. It is a raw fuel smell. I do not believe it is a cracked Y pipe.
 

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The most common external places to get a leak are at the filters (caps primarily) and at the regulator housing on the side of the upper filter. That being said, you should see the evidence of the leak around the filters. Are you seeing any white smoke from the exhaust? Your oil level isn't unexplainably rising is it?
 
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Stuck in Commiefornia...
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Let it idle in one place for a good 5-10 minutes. Shut it off and slide under it. Look for anything that shouldn't be wet with a really bright flashlight. You have plugs in the back of the heads, that can possibly leak, as well as flexible braided fuel lines on the drivers side that run past the exhaust manifold at the front. The other thing you can do is pull the air filter assembly out to get a really good look in there for leaks. Finally, check the coolant bottle just to be sure you don't have fuel in it. The fuel system is under higher pressure than the cooling system, so if you have a bad injector cup or issue with a head, you may find fuel in there and the cap will vent the pressure over 16psi.
 

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Dually Club #3
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Discussion Starter #6
Bismic-No to both questions.

IdahoF350-I will do what you said to check for those leaks.

So far I haven't found any leak or evidence of a leak. I will continue to investigate.
 

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I had the same thing I could smell fuel when stopped or going slow but not at highway speeds. My fuel pressure regulator was leaking, it was the perfect time to do the blue spring upgrade. The full kit comes with new gaskets and a new cover it fixed my problems.
 
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Dually Club #3
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Discussion Starter #8
I will check the fuel regulator. But I can't find any fuel anywhere on this engine. I guess it could be the exhaust up-pipes but just doesn't smell like exhaust.
 

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Stuck in Commiefornia...
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Ok, so you have fuel from the HFCM on the drivers frame rail to just forward of the engine crossmember, up to the upper fuel filter at a Banjo bolt with two copper washers. From the fuel filter assembly you've got two hard lines, attached with banjo bolts and copper washers at the filter housing and the cylinder head. The fuel passage runs the length of the head and is plugged with a single copper washer to seal it. The filter housing has it's plastic cap sealed with an o-ring and on the front of the housing there is the fuel pressure regulator which seals to the housing with a molded o-ring. The fuel return line then follows the feed line back to the HFCM. Just about at the same level as the exhaust manifold there are two quick connect fittings and some braided flex line, the fittings have o-rings in them to seal the connection, as do all the quick connect fittings on the HFCM and at the tank.

That is your fuel system, if you check all of the points mentioned and there is no sign of fuel loss, then you will want to look closely at the bellows on the up pipes for signs of exhaust leaks, also the EGR cooler v-band and turbo to y-pipe v-band connections as it is possible to have a misalignment and a small exhaust leak from those points. Unlikely to be the exhaust manifolds at the heads, but still give a look there, especially the passenger side as it's closer the the cowl vent, and inspect the connections at the up pipes to the exhaust manifolds to see make sure you don't have any broken bolts.

It's quite a lot to check thoroughly, but can be done in an hour or so, and a cell phone video camera with a light can aid you in looking at areas that you simply can't see because you can't get to them with anything more than your hands. And if you have to use your hands, buy a pack of nitrile gloves, play proctologist and stick various fingers in dark places. When you check your fingers on the glove, if you see black soot, or a fluid that ends up smelling of diesel, well, then you've found the source of your fuel smell.

Good luck, keep up posted of your findings!
 

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Dually Club #3
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Discussion Starter #10
I have finally found the leak. It is the fuel regulator on the fuel filter. It has been dripping down on the radiator hose to the where I assume the thermostat is on the drivers side of the engine. The heat from the coolant hose has been causing the diesel to vaporize and "dry" so I was not finding any drips. It has gotten worse now and the entire area is "wet" with diesel. I have ordered the blue spring upgrade from Amazon for $61. So do to the leak I get an upgrade as well!! Thank you all for the help. This one stumped me for awhile
 
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Good call Bismic and wvsdmf11!

Harry
 
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Dually Club #3
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Discussion Starter #12
Yes, Good call to both of them!!! Just took a while for the evidence to show itself!!
 

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Dually Club #3
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Discussion Starter #13
I found the blue spring upgrade rebuild kit on Amazon for $58. Installed today, started up, no leak. Was doing a thorough once over of the engine and found that the turbo out boot was very oily. Removed it to clean it and found a large split in it. Hadn't even notice a boost leak. With a bad as this leak is, it was leaking boost and decreasing my performance.

Question is: replace all boots with a kit, or go to Ford and buy just this boot? I found a few on Amazon and do not like the how they look. There is no ridge inside to help hold the boot in place.

FYI, I am running stock intake and tubes.
 

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I went with a complete kit from BD I like the boots and clamps better than OEM.
 
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The Riff Raff boots seal very well and are reasonably priced. Clay at Riff Raff is a great guy.
 
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Junior Member
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Had a similar issue

I have developed a raw fuel smell when sitting at stop lights, or slower speeds in town. The smell dissipates at highway speeds. I have looked high and low for a fuel leak and have not been able to find one. My fuel mileage has also dropped about 2 mpg for the last two tank fill ups. Has anyone had this issue, know where to look?
I had a similar issue and it turned out to be the O-rings and gaskets on the fuel pressure modulator. Apparently, Ford reused the old gaskets when they replaced the spring in the fuel pressure modulator.
 
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