NEED HELP!! My 300 gets 3mpg!!!

I got a 300 inline 6 with a c6 trans. It previously got 16mpg and now its gettin 3mpg. I cant figure out a bit why. It dosent run rich or leak gas. If anyone can help I would really appreciate it.

 

leaking gas tank?

 

with no obvious signs of wasted fuel, I'd be checking my math.

 

Ive checked everywere and cant find a leak. I have a 13 gallon fuel tank and can only go 47 miles before its empty.

 

Is this reoccurring or just one time? Some meat head siphon your tank?

 

Its very consistent, been gettin the same milage for 4 months...

 

One traditional hazing is to siphon a guys gas for a few days then put it back -can drive the right nuts

 

1. Someone is siphoning your fuel.
2. If you can't find leak when it sits, maybe a leak after the pump when engine is running.
3. If it has a mechanical pump, the diaphram in the pump may be leaking into the crankcase.
4. All the fuel may not be siphoning from the tank.

 

That just aint right

 

I can watch the gas gauge drop while im driving!!! And I keep monitoring the oil in the crank case and theres no change there. It has me stumped, Im starting to think the motor is killed.

 

If it isn't leaking it is consuming it, it really is that simple. So now you need to figure out where it is going. Check the oil, if it smells like gas you may have a bad mechanical fuel pump. Start the truck and look down the carb throat with it idling. Is it dripping fuel off the venturi? Is it a holley 2 barrel? Does it have a power valve? if it does it may be ruptured. There really aren't that many options, you just need to start eliminating things.

And at 3 MPG, it shouldn't be that hard to track. Thats a ton of fuel.

It's going somewhere.

 

if in 4 months you havent found the problem ...... sell it !

 

It has a 1bbl carb and it sprays a mist of fuel when idling. as far as i can tell it runs how its sopposed to.

 

Before this thread turns into a guessing game, why dont you tell us what you have checked?
A lil more info would go a long way.

 

Ive checked for leaks, I checked the trans, I checked the crankcase for fuel, It aint runnin rich, no one is stealing my fuel,The motor has 419k miles and I rebuilt the 1bbl carter carb. Ran excellent and still runs excellent but the milage dropped from 16 to 3. Thats all Ive checked and If I should check anythin else let me know.

 

does the exhaust smell like fuel? check the plugs to see if theyre wet with fuel....and then check to see if your spark is hot enough. you may just be blowing the fuel through your exhaust.??

 

I got autolite plugs and the exhaust dont smell like fuel. Im gonna go pull the plugs and take a look at em.

 

I don't think the engine would even run at that rate of comsumption. But check the sparkplugs...see if they're black. But again...if it was burning that much fuel, it definitely would foul the plugs, and then start running really crappy.

If the plugs aren't fouled, which I doubt they are if it's runnin' good...you've definitely got a leak. It may be near the engine or the exhaust pipe, and drying off quickly enough, that you can't see it. Look again...real closely.

 

I find it hard to believe it would even run at 3mpg. It would certainly be smoking black smoke

 

does it waste the fuel if you just let it sit and idle or just driving? may have a hole in the tank so it drains as your driving. Just a thought

 

that t,rantula is really badass, how far is the engine set back?

 

One other idea. Where does your fuel exit the tank?...at the top? If so, it may be leaking there, and hard to see.

 

Hard to imagine that you could force that much fuel through a 1 barrel carb in that amount of time. If you could, it would have to be combined with the right amount of air to run right, and that is also unlikely. I would think that it has to be leaking somewhere.

 

When you look for the leak, don't just look...feel too...with your bare hand. And smell.

 

[QUOTE="T'RANTULA";7421570]Ive checked for leaks, I checked the trans, I checked the crankcase for fuel, It aint runnin rich, no one is stealing my fuel,The motor has 419k miles and I rebuilt the 1bbl carter carb. Ran excellent and still runs excellent but the milage dropped from 16 to 3. Thats all Ive checked and If I should check anythin else let me know.[/QUOTE]

Is this a typo? If not than holy crap.

 

Have you ran out of gas while driving? it sounds like the fuel gauge isnt working properly. Sounds like your getting the milage of a top fueler! Maybe after 419 K you should think about a rebuild.

 

I just pulled the plugs and the motor is still hot. The plugs are a blueish white color but not black. I got a new gas tank with new fuel line and ive dissassembled the bed and looked every were for 4 months and i cant turn up a leak. This just seems to be insane! I do have a couple bad lifters in the engine but I dont think that could cause this problem?

 

Be sure to check, both while the engine is running and not running.

One other thing. If you can avoid it, don't use a regular trouble light...danger. One drop of gas on the light bulb, and fire. Use a fluorescent trouble light or a flashlight. Good luck. Let us know.

 

Not a typo

 

I beleive 10 inches cant remember right off hand