[Krokus_96F350]

Does anyone have any idea as to why on my 96 F350 I would get different mileage figures with my tanks? On the front tank I can go 310 miles, but on the rear tank I can only go 200 miles and sometimes even less.

Aren't they both the same size, 17 gallons? The engine runs the same from either tank.

I'm stumped.

 

[MilitiaAir]

the rear slightly smaller than front but only by like a gallon or 2. Thats a big diffrence!. If your running that tank till it starts to stall and you get those numbers I would drop the tank and see if the rubber boot feel off the end of the pickup. I cant think of another reason. If your trusting the gauge I wouldnt. My gauges read F at half of tank still and than skydive down to the red when empty. Its amazing to go like 140 miles before I drop below F than in 70 miles be empty! Tank is easy to drop and look tho granted the tank is empty!

 

[firman]

what mods do u have to get that kind of mileage from one tank, the best i can get with either tank is 200 miles.

 

[Believer45]

Do you run the front then the rear when you fill up? If so try running the rear first. If the rear then gets more miles you probably have an issue with your selector valve leaking fuel between the tanks. If this is what is happening then while using the front tank you may be pulling some fuel out of the rear tank as well.

Have you run the tanks all the way empty? I have done so to make sure how much fuel they hold. You need to time it so you "run out" while on the interstate (trips work great for this) so you can switch to the other tank and use the truck's momentum to get fuel back into the fuel system. You may also have an issue with the rear tank sender not being accurate - it may say empty when you still have 1/3 tank or so.

Dave / Believer45

 

[ammayernick]

I thought they were 19 gallon tanks?

 

[bbforce]

According to the owners manual...on a crew cab truck the tanks are 19 gallons up front and 18 gallons in the rear

 

[Krokus_96F350]

Re

Thanks all you guys for all the possibilities.

My F350 is bone stock except for a 3" downpipe into a 4" exhaust.
I have 233,000+ miles on it now and it still runs great. (Knock On Wood)

I always run the rear tank first, then switch to the front. I have never run either one empty, I fill them when they read 1/4 and they both seem to take the same amount of fuel when refilling.

I like the response about the sending unit maybe being bad, to test it I guess I'll run the tank dry and see how many miles it takes for the truck to starve for fuel. I just hope I don't pick up a dead squirrel or something from the bottom of the tank.

Thanks again guys, take care!

 

[bugman]

I have owned 3 Fords with dual tanks and the rear one has never read right on any of them. The only way to fix it is to pull the rear tank and adjust the float and retry. This may take quite a few times so why even do it unless you are a stickler for accuracy. The best way to figure mileage is to hand calculate it and not go by the gage. On my truck I can put 19 gallons in the rear and 21 into the front.

 

[Griz]

Another thing to consider is how full are you getting your tanks. I installed Dale's filler neck tank mod in both my tanks and was amazed not only how easy it is to fill the tanks but how much more fuel I could get in them. By not refilling them the same each time can throw out your mpg figures. Just my 2 cents.

Griz

 

[drwoodchopper]

What is your actual mpg's per tank does one get like 20 oand the other 11? Try running front then filling and checking then the back and filling and checking and don't switch over before you fill up.

 

[Krokus_96F350]

Re

Another thing to consider is how full are you getting your tanks. I installed Dale's filler neck tank mod in both my tanks and was amazed not only how easy it is to fill the tanks but how much more fuel I could get in them. By not refilling them the same each time can throw out your mpg figures. Just my 2 cents.

Griz

I'm new to this site so I am unaware of Dale's mod for the filler neck. I fill both tanks with as much fuel as I can cram in them. When I see the fuel in the fillernecks I stop. I get about 14 or 15 gallons into each tank, which nets me about one weeks worth of driving to and from work.

Is there an equalizer tube between the tanks?

 

[Believer45]

No equalizer tube, you have a fuel tank selector that chooses which tank to draw fuel from and which tank is showing fuel level on the dash gauge.

 

[Krokus_96F350]

Re

What is your actual mpg's per tank does one get like 20 oand the other 11? Try running front then filling and checking then the back and filling and checking and don't switch over before you fill up.

Great Idea! That would give me proof that an not going crazy.

 

[Snowtow]

According to the owners manual...on a crew cab truck the tanks are 19 gallons up front and 18 gallons in the rear

Cab configuration has nothing to do with it. It's the bed length that determines the tank capacity. Rear tanks are the same for both short bed and long bed. On a short bed the front tank has a smaller capacity than the rear (16.x gallons).

 

[tly]

My 83 and my 89 both had a return line for the unused fuel, if the transfer switch is not functioning correctly there is the ever so slight chance you could be pulling fuel from one tank, and the returning fuel is going to the other tank.
if this situation happens you would get different mileage from each tank, depending on which tank you took fuel from first, you could overfill the tank you are not using, this transfer switch / valve, very seldom goes bad, but it can leave you thinking your running off one tank when in fact you are on the default tank, if the switch goes out the gauges will switch tanks but your fuel draw will not, I don't remember which one is the default tank, but it would "normally" be the larger of the two.
At least that is a problem the designed out of my 07, until I put a tank in the bed.

 

[4micaman]

I'm new to this site so I am unaware of Dale's mod for the filler neck. I fill both tanks with as much fuel as I can cram in them. When I see the fuel in the fillernecks I stop. I get about 14 or 15 gallons into each tank, which nets me about one weeks worth of driving to and from work.

Dale is Dale Isley, owner of Tymar Performance in Spokanne, Washington. You'll see mention of his name and company a lot here. I just talked to him yesterday for the first time, very nice and knowledgeable fellow. Contact him at 509-922-8785

The filler neck mod is a kit to aid in faster filling of your tanks and so you can fill into the neck without spending 30 minutes doing so.

 

[MilitiaAir]

what mods do u have to get that kind of mileage from one tank, the best i can get with either tank is 200 miles.

I get about that. Sometimes I get up to about 230 miles on my front tank and about 210-220 on my rear tank. But like I said I kno exactly where my fuel tanks run out lol. All my mods are in my sig. Really thats horrible mpg compared to alot of other PSD's. I normally only shove 16-17 gal in front and 15-16 in rear for a total normally equalling 32-33 gal. Averages range from 13-15mpg depending on what all I shove in the truck. I normally tote all my recovery gear and all my tools plus 105 gal tank which always has fuel in it norm.

 

[Griz]

Dale is Dale Isley, owner of Tymar Performance in Spokanne, Washington. You'll see mention of his name and company a lot here. I just talked to him yesterday for the first time, very nice and knowledgeable fellow. Contact him at 509-922-8785

The filler neck mod is a kit to aid in faster filling of your tanks and so you can fill into the neck without spending 30 minutes doing so.

The above info is correct. If you get a chance check out your filler neck and you'll notice it really is two hoses. The inter hose is where the diesel flows into your tank and the outer tube is "suppose" to vent the tank. The problem is with diesel it foams a lot and this blocks the vent hose because it is pretty restrictive. Dale and others have designed a kit that removes the inter hose and you weld on a fitting to the neck for the new vent. Not hard to do if you follow Dale's instructions. :thumbsup: I can't weld but I took the fitting and filler tube down to a local muffler shop and they welded the fittings on for a couple of bucks.

Griz