Truck smells rich and getting bad mileage?? - Diesel Forum -
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 4 (permalink) Old 12-09-2010, 08:37 PM Thread Starter
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Truck smells rich and getting bad mileage??

I've been noticing that my truck just seems to be getting bad mileage and I can smell alot of diesel fuel smell, but I have no leaks any where. I'm getting about 13-14 empty and thats babying the truck around where as I used to get 16-17 running around not really thinking about fuel mileage. I have been pulling my new boat alot lately which weighs about 5500 pounds which I don't feel is all that much weight but I really notice it when pulling and only getting 9-10mpg. I've been pulling 20+ ft enclosed trailers for years and never really notice the load and would still get about 13 mpg. It just seems I have to lay into the throttle more to keep mph constant on the interstate and Im only running about 60 mph. I used to pull my 12000 lbs toy hauler 75-80 with no problems.

I checked for the tube that comes off the exhaust manifold to see if it was clogged and my truck doesnt have it on the truck (I made a post about it about a month ago). I checked to see if I had leaking manifolds and tubes going to turbo but I don't see any black soot and can not feel any leaking around the pipes when the truck is running. The truck does seem louder of a 7.3 cackle (for lack of better words) when driving down the road and takes more throttle input for it to go away.

I've been doing searchs to see if others have had similar issues but haven't seen anything. I was curious about a injector issues and did some research but I don't know. The truck starts right up, idles fine, even drives fine minus the bit low on tq. One thing that is might be worth mentioning. Running down the interstate about a month ago I was late for an apointment and I was running about 85 and the truck just started POURING black smoke out and I wouldn't really felt out of steam. I don't have any ses lights flashing so I'm not sure whats going on.

Sorry for the book and thanks for any advise.

99 f-350 CC dually
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post #2 of 4 (permalink) Old 12-11-2010, 09:32 AM
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The fuel smell makes me think it's the water/fuel separator drain valve. I had similar issues and that's what I found. Make sure to check with the truck running and pressure in the fuel system.

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post #3 of 4 (permalink) Old 12-11-2010, 10:05 AM
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It doesn't take much fuel in the valley to put an overwhelming stench in the truck, particularly when the valley warms it up and the fan pushes it back at the cab. As for the black smoke and lack of power, perhaps the two are related. Black smoke is typical of too much fuel for the available air. If your boost numbers are low, you won't be making as much power and milage will drop. Whats the condition of the air filter? There are also several spots on both the exhaust and intake sides that can be leaking, affecting boost levels. If it's on the exhaust side it can put a diesel fume smell in the truck too. The ehaust side has the manifold to the block, the manifold to the up-pipes, the up pipes to the collecter, the collecter to the turbo, and then the turbo to the downpipe. The up pipes to collecter joints are difficult to see but have a dougnut type gasket in them which can go out or simply loosen. You will see some soot around them if they are leaking. Oddly enough, an exhaust doughnut from a SB chevy will fit. On the intake side there are of course all the boots that need inspected. You cannot check them by feeling at idle since you're not building any boost at idle, and I don't recommend trying it while driving 60mph down the road. The turbo itself can receive damage and not give you sufficient boost too. There's also the wastegate on the turbo, which needs to stay closed normally.

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post #4 of 4 (permalink) Old 12-11-2010, 08:29 PM
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Climb on top of your motor and look around your fuel filter housing and into your engine valley. I had been getting a strong diesel fuel smell at start up. Turned out to be my fuel filter housing leaking diesel everywhere. I just rebuilt it and no more diesel fuel smell. My fuel milage has also been down awhile, but I only have a few days on the truck since the rebuild so I can't say whether I have gotten any milage increase. I never noticed a difference in power though. Maybe you have multiple issues and this is just one of them.
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