Smelling Fuel and Lousy Gas Mileage

[MWHurt]

Hey Gents, I have a 67 lwb stepper with all original drivetrain, 250, 3ott, even the original points distributor! When I cruise down the road, I can watch the fuel gauge go down, and when I make a quick stop at the store or something and get back in the cab, I get a decent buzz off the gasoline fumes. My un-checked calculations put my fuel economy at about 3-4 mpg. The truck sat for about a year while I was on deployment, and I'd like to get her running better. I'm not sure what carburetor I have, but I'm sure it could use a re-build. Any help on identifying the original carb or suggestions would be greatly appreciated.
Semper Fidelis,
Mike

[Mock1]

Welcome back to the good ol U.S.A.
Thank you for your service.
If your rig has been sitting a while, several things could be working against you.
1. Gasoline starts separating after about thirty days, and it turns into kinda like honey after a few months. Unless you used stabilizer in the fuel before you left, chances are that gunk is all in the fuel system and it can cause lots of problems.

2. Your points type distributor could have rust built up in it where there is carbon steel parts and oxidation on the aluminum. Moisture build up under the cap can also be a gremlin. Also, check ALL your spark plug wires for cracks, burn spots, or just replace them all together. And definitely check your plugs.

3. Check ALL or your fuel lines, from the tank to the pump, from the pump to the carb, replace the filter. Check the tank itself to make sure it not rusted through, even if that means pullin it out. Replace the sending unit gasket, just to be sure.

I dont know jack about your carb, but posting a few pics could help the gurus here to I.D. it for you. Sounds like you just need to do a basic tune up, and fuel system flush, change the oil and filter, change clutch fluid if hydraulic.
Also, check you tire air pressure. You'll be surprised what a difference the proper air pressure will make.
Good luck.

[69chevy lwb]

If it runs really bad at low rpm but picks up around 2000 it's possible the choke is stuck on. My 292 did this I watched the gas gauge move as I drove It and it had about 6hp

[MWHurt]

Thanks for the direction folks. Looks like I need to spend some money at the parts house and a good weekend of tinkering!

[davepl]

Start with the basic tuneup. When you see hoofprints, think horses, not zebras.

The choke adjustment, including the very important pulloff, are part of that, so don't skip it.

I'm going to guess that the vacuum diaphragm that pulls the choke off either has a crack in the little vacuum line that feeds it or in the diaphragm itself. It's a long shot, but it's a shot. I'm thinking the choke pulloff fails to do it's job, so the choke stays closed too long, but if you open the throttle far enough it'll be forced open, and that's why it runs better. If there's a vacuum leak that could exacerbate your symptoms.

Now that I think about it, if I recall correctly, choke springs work in opposite directions on big blocks vs small blocks. I don't know if that means they -work- backwards, but if so, then a broken or weak choke spring might do it, but I have to think that the spring is always used to close the choke door regardless of the linkage direction. But I do not know for sure, and know even less about the inlines.

[GASoline71]

Check all of your fuel lines for leaks. The 250 isn't known for it's fuel mileage either. Just because you have an I6 doesn't mean better fuel economy. A lot of 6's get worse mileage than V8's because you have to keep your foot in it more to move that heavy truck. Just something to think about.

Gary

[EARNHARDT#3]

Originally Posted by davepl

Start with the basic tuneup. When you see hoofprints, think horses, not zebras.

The choke adjustment, including the very important pulloff, are part of that, so don't skip it.

I'm going to guess that the vacuum diaphragm that pulls the choke off either has a crack in the little vacuum line that feeds it or in the diaphragm itself. It's a long shot, but it's a shot. I'm thinking the choke pulloff fails to do it's job, so the choke stays closed too long, but if you open the throttle far enough it'll be forced open, and that's why it runs better. If there's a vacuum leak that could exacerbate your symptoms.

Now that I think about it, if I recall correctly, choke springs work in opposite directions on big blocks vs small blocks. I don't know if that means they -work- backwards, but if so, then a broken or weak choke spring might do it, but I have to think that the spring is always used to close the choke door regardless of the linkage direction. But I do not know for sure, and know even less about the inlines.

He's got a '67 with a 250. Manual choke on that baby.

[briscuba]

A couple guys already mentioned check fuel lines. Include a check of inside the cab if you have your tank behind the seat. If I recall 67s have a folding seat, makes it easier to check the lines into the tank.

My two cents...

['68OrangeSunshine]

Hey Mike Semper Fi!
Your carb is most likely a Carter YF [? '67-only] or Rochester Monojet. Rebuild kits should be locally available. Choke should be manual, cable-actuated from the knob on the dash.
I changed out my Monojet for a 4Bbl Holley 390 on my 292, years ago, so I'm no source for a one- barrel R&R.
Next time you deploy put 40 Oz of Sta-Bil in the 20 gallon tank. I was lucky, my Dad watched my '68 C/10 Stepside while I was PCS'd 1MAW WestPac in the Mid '70s. When I was at MCAS CPNC trucks like ours [yours especially -- 250, 3OTT] were the Issue CUCV. I had to get a military drivers license from the Motor Pool in a '67 Stepside, 250, 3-speed Saginaw. When I double-clutched around a corner, the Motor Pool check rider Corporal yelled at me to "Quit hitrodding 'HIS' pickup!''

[Greasey Harley]

Food for thought:
If you are running ethanol fuel, you MUST treat it!!
Ideally you should NEVER run ethanol in a carbureted vehicle but, sometimes you don't have a choice.
I own a boat repair shop, I recommend Star*Tron, it works . (It doesn't work as well as keeping the ethanol out but, it works)
USE IT EVERY TIME YOU FILL UP (with ethanol fuel).
I would also use Stabill if you are going to let it set for an extended ammount of time.

The boats that I preform this treatment on (for my customers), seem to store fairly well for the long winters.

My shop gets A LOT of business due to ethanol related problems.
Generally, we just Replace everything. All rubber lines, fuel pump, flush tank and metal lines, rebuild carburetor, etc.
I always tell people "spend a few extra bucks for non-ethanol gas, or spend a few HUNDRED extra bucks, for me to rebuild your fuel system."

I'm not saying this is your problem, it's just that, in my experience; Ethanol is responsible for the majority of carbureted fuel system problems, these days.

...and I fix a lot of carburetors.
-R

[Wrenchbender Ret]

Watch your fuel pump with the engine running. Often you can see fuel spraying out the vent hole. That means a bad fuel pump. Also check the engine oil to make sure gas has not gotten into it.

[kolle_hond]

If you think it might be the choke, try and block it off like mine is (I got it this way). There is a pipe running to a small filter at the front of the truck, just remove it from the filter and plug it with something. My choke cable is stuck, so I never bothered reconnecting it, as the truck runs fine. I got around 14.3mpg on the open road with the same engine, keeping in mind that I have one misfiring cylinder. I was told that I should be able to get about 18.8 mpg after getting the valves fixed. Good luck with the fix!