My fuel mileage just dropped like a rock

[smokejunkie]

As you can read from the title my fuel mileage just dropped like a rock:{

About a month ago I fueled up and went on a little weekend trip 300 miles and I'm out of fuel. I thought no big deal probably just the fuel filter. So I changed that promptly after that trip and no change, so I bought another air filter changed that too. Still the same problem. I'm only getting between 9-10 mpg empty around town and highway driving, no towing. I normally get 15ish with mixed driving. Nothing else has changed since that intitial trip where I thought I maybe got some bad fuel. 1 month before this I installed HTB2 turbo and pulled the 5er over easter and did wonderfully. I can't figure it out. Any ideas on what else to check?

other mods are edge juice, afe, ats transmission

 

[bmoeller]

Internal or external fuel leaks? Fuel in oil?

 

[TAbbott]

Turbo boost leak? Running too rich will make your fuel mileage go down... . It also may be time for a valve adjustment. Valves too tight and mileage drops fast... .

 

[smokejunkie]

Boost is the same as it has always been as far as I can tell. What do you mean by running too rich?

thanks for the replies

 

[smokejunkie]

Internal or external fuel leaks? Fuel in oil?

no external leaking. How would I go about checking for internal fuel leaks.

I'll check oil tomorrow.

thanks

 

[TAbbott]

"What do you mean by running too rich?"



Too much fuel for the amount of air you're pumping into the cylinders.

 

[p-Bar]

as said before check your oil level you could have a bad injector washing out a cylinder.

 

[PTomlinson]

Any neighbors with a diesel and syphon hoses? I know it sounds like a bad joke, but with the price of fuel I wouldn't ignore the possibility.



Paul

 

[smokejunkie]

oil level is right in the middle of the OK range

 

[Grey Wolf]

Any neighbors with a diesel and syphon hoses? I know it sounds like a bad joke, but with the price of fuel I wouldn't ignore the possibility.



Paul

Yep, do you have a locking cap?

 

[JVas]

Check for a binding U-joint. I had a 2 to 3 mile per gal. drop that was a bad joint. I caught on to it when the truck stopped rolling down the driveway when I released the clutch.