I've got a 302 driven '82 F-150. It never really got good milage. When I got it, it got around 6. I got it up to around 9 recently. Earlier today, I decided to change the fuel filter, seeing as it's probably been there for a little too long and is probably half clogged. I figured that might help performance/milage a bit. So, I swapped in a new filter (exactly same design as previous) and went about my business. Later in the day, I was going to go somewhere (not a long trip, maybe about 4 miles) and I jumped in the Ford. It performed no differently, but what was different was the visible movement of the fuel gauge. When I got there, I popped the hood and checked for leaks around the filter. Nothin. Solid connection. Checked for leaks elsewhere, once again to no avail. When I left, as I went down the road, I once again watched the gauge visibly move down. I went about 8 miles and used between 1/8 and 1/4 of a tank!!!
Now, I've posted before trying to figure out exactly what carb I have, where the mixture screws are, etc. I believe one person took a stab at it. Thus, I still have no idea how to turn this damn thing down.
I'm thinking of putting the cruddy filter back on there until I figure out what's going on. Apparently, the cruddy filter was keeping it from wasting so much extra fuel. I've even gotten the crazy thought of putting a 1/4 turn valve in line before the filter so I could keep it from putting too much fuel through the carb.
OK, now here's where y'all have your chance to shine. If any of y'all have any idea what exactly's wrong with the carb (I'm thinking power valve's shot) or where the mixture screws are on an assumed 2150 (refer to "help IDing and adjusting this carb" for picture) or any other bright ideas on how to redneck it without spending any or that much money, post away. I can tolerate 7-9mpg, but this kind of gas usage is nuts.

 

Youre absolutely right, that is insane milage! a friend of mine drives an 86 with a 302...its fuel injected unlike yours, but it has gotten up to 20 mpg on the highway and averages somewhere around 15 when hes easy on it. so yes, theres definitely something wrong. ive had the same problems on my truck, where a sub ten mile errand drained a full quarter tank and left me wondering where it all went. one thing to remember, is the gages are fairly erratic on those years, i know mine is. sometimes after letting it sit for a day, if you go back and turn the key half way it will go back up to where it should be...other times it doesnt come back. who knows...anyway, if the gas really is leaving the tank, its either leaking out on the pavement (have you checked for leaks while its running?) or being burned, or partially burned as the case might be, in the engine. does it run rough at all? does it puff black smoke when youre driving? are the spark plugs fouled and wet? those are easy ways of telling if its taking in too much gas. hmmm, as for adjusting the carb screws, even if they are way off, that should only hurt your milage by 1-2 mpg, i dont think those being tuned wrong could be raping you as bad as youre getting it right now. oh, when is the last time youve tuned it up? (plugs\wires\cap\rotor\adjust timing etc...) those things can have a huge impact on your milage. well thats about all that comes to mind. get back to us on more details.

 

It's been running extremely rich every since I got it. The inside of my tips are like black holes. Wipe your hand around the edge and people'll think you've been in the coal mine.
Changing to Bosch Platinum plugs, among other things such as cleaning the carb (carb and choke cleaner, I haven't opened it up yet and ain't really wantin to if I don't have to), using non-ethanol fuel, and improving air flow was what got me from 6 to 9.
The cap and rotor weren't very old when I got it (January) and the wires are, well, shot, and on my priority list for replacement.
I haven't checked the timing, but it doesn't seem to be missing too horribly. I'm sure the timing is off a little. I'll be takin my other truck to Clyde's pretty soon to figure out the extreme spark knock(the irony, one truck rich, one lean!) so I guess I should just take the Ford in while I'm at it.
I had checked for leaks while the truck was running and there were no leaks. All that fuel was going into the carb. Where it went from there, who knows.
Plugs used to foul real bad, but the Bosch Plats don't.
She runs real well, but has a habit of flooding if stopped and then restarted soon after. Also, it has a habit of bogging momentarily at the beginning of heavy acceleration, almost like a TBI, once again due to too much fuel getting into it.
From my observation, her milage went from bad to unacceptable with the changing of the filter. I filled it up Tuesday and only put 15 miles on it before I changed the filter and took the 8 mile round trip. I'm used to the gauge and know that it usually doesn't move off the full mark (appearingly 1/4 past F) until about 30-40 miles have been put on it. With a mere 23 miles on that tank, it's sitting towards the F end between 3/4 and F. I think the old filter was covering up the problem by restricting the amount of fuel that was let in. Same principle of my insane 1/4 turn valve idea, except I can control how the valve performs.
1-2 mpg, while little gain to some, is a godsend to a truck getting less than 10. Hell, I'm shootin for 12 highway when everything's workin right.
I'm starting to seriously consider taking up a friend of mine on an offer of the EFI off his old 302. I almost think it'd be easier to convert to that, and just make it all work than it would be to get this carb to work efficiently.

 

It's possible the bowl float or the chocke could be sticking. Make sure no carb gaskets are leaking. Look for stains on the manifold because the gas will boil off. Tough to tell without looking but if that much gas is going into the engine I wouldn't think it would run right. Also check the oil, see if it's contaminated with gas. Good luck.

 

Definitely check to be sure the choke is fully open and stays fully open when warm with the throttle open and closed engine running.
The float could be adjusted too high causing fuel to drip into the intake. Look into the venturi while someone turns off the engine, the fuel flow should not continue to drip.
Could someone have installed larger metering jets in the carb?
Mark

 

Another thing to check is the "power valve". These are often an overlooked problem source. I would also check to see if the carb base gaskets are damaged. Maybe a re and re is in order. I wish I had your problems. I have a F.I.motor and without major expensive equippment it is real hard to troubleshoot for the shade tree mechanic.

 

im leaning towards something wrong with the float, becasue u said when u put a new filter on it , it got worse, well if needle is not closing that would put more gas to the motor, i just dont see how it could run using that much gas....it must pour out black smoke an unburned gas?

1985 F-150/351Ho/4wd
1979 f-250 429(stout 460 on the way)/4spd/6in w/36's,Dana60/44hd,3.54 gears~4.11's comin soon

on a quiet night your can hear a chevy (lol,you can watch a dodge) rusting away

 

Thanks for all your input so far. Sometimes basic things slip my mind. Power valve and float had crossed my mind though. I'm aware the dang thing needs a rebuild pretty bad (guess I just needed somebody else to confirm it,) but I don't have a whole lot of time to mess with it. With the information provided, do y'all think an in-line valve before the carb would work to take up the carb's slack until I can do some real work on it?
I topped off the tank today and checked my milage. It came out around 3mpg. I took the truck home, put the old filter back on it and drove it around all over the place for a good while. Then I went back into town, topped her off again and ended up with 9.5mpg for that run. It seems a little better now than before I juggled filters. The clogged one still seems to be helping me out better, and who am I to argue with results? I smell less gas in the exhaust and no longer see black smoke, even when I romp down on it. It seems better than it's ever been while I've owned it, even though I simply returned it to the way it was. Maybe I accidentally improved something while doing all the filter swapping.

 

wow, that sucks. as the others said, its likely the power valve or the float. however, as you said, you dont really wanna tear into anything, and your idea of installing a valve before the carb would act as sort of an "auxilary" float, only letting in how ever much gas you want to let in...sounds like a good idea to me. if you have one laying around, throw it on and give it a try. i would bet you would see some good milage gains. give it a try and let us know how it turns out.

 

If you don't want to mess with taking the carb apart you can always get a rebuilt from a parts store to save the hassle. If not ,do you have a hose section in your fuel line, if so you can put a clamp on it to slow down the fuel flow, or put a restrictor, like a nail, before the fuel filter in the fuel line to restrict the size of the line therefor reducing fuel flow. I once had a G.M Jimmy ( shame on me) that had the exact opposite problem, got 30 plus mpg!! Turned out that the fuel pump only put out 3psi instead of 9, It ran great on the flat but had no power for hills. I put a new pump on and cured the power problem but the milage went back to 15mpg. Now if I had installed a flow regulator for 3 psi and a bypass valve to give full pressure
when needed maybe I could have had the best of both worlds....
but now I have this f.i 5.0

Perhaps your float has a hole in it(brass type) or is saturated(Phenolic type) Float needles can go sour too. Also carbs can erode or rust out causing leaks into the venturis.

 

You need to take a look at the carb my friend. That really is insane mileage!

 

the other thing you should be concerned about is fuel washing of the cyls. using that much fuel it can wash the oil off the cyl. walls causing metal to metal contact and destroying the cyl. walls.