[66mustangx2]

I have a 1966 mustang c code 289, when I go up a steep mountain the car starts cuttin out and stuff and i smell gas but no sign of gas when i stop and check. This only happens going up a mountain on flat ground the car runs great .I replaced the sending unit and pickup tube about 2 years ago, any help?

[1967_Red_Stang]

I recently noticed a strong smell of gas in my 1967 and my car would hesitate occasionally under strain. I traced it back to a leaky fuel pump that was starting to go bad. Once I replaced the pump, the car is working great. I am thinking you could have an issue with the fuel pump not pulling enough fuel into the engine.

[Veronica]

Hello. Going up ( or down) a steep mountain drasticly changes the angle that the carb is sitting, and, consequently, makes the float level be functionally way to high. How carbs work, the simplest, quickest terms imaginable, is by a pressure differential. The air going through the venturis of the carb is at a much lower pressure than the normal atmospheric pressure. The float level in the fuel bowl is set to be just slightly below the discharge nozzles in the carb. That's why there's a vent on top of the fuel bowl. The normal atmosperic pressure at sea level is between 14 and 15 p.s.i. The air pressure at the discharde nozzles in the venturis varies considerably, depending on the velocity of the air traveling through there, but it's never more than like 8 p.s.i. when the motor is running. 14 pounds pushing on the back side of the fuel and 8 pounds pushing against the front side is what causes the fuel to go through the carb. When you stand the car up on it's rear end by going up a steep mountain, that puts the fuel level way up above the discharge nozzles and then it's the gravitational pull of the entire planet moving the fuel through the carb. You get a lot more fuel running through there like that. The old Broncos had a baffled fuel bowl to try to minimize this, but, there isn't really a whole lot that can be done to stop this entirely on a carbureted car.

That could be what's going on with your car.

[Ivy66GT]

Darrell,

I apologize in advance but I just couldn't resist: Where in Alabama do you find a steep mountain to drive on?

Veronica just about covered it. It has a carburetor which is meant to stay upright. I don't think Mustangs had an off-road option to help with that.

Since the 2-barrel vent is at the front of the housing I would have thought it would leak and therefore smell more strongly when you go down a steep hill instead of up. Is that the case? Or possibly you are smelling gas from the exhaust when the engine starts missing a lot? That would explain why you only smell it on the way up. On the way down the engine is hardly doing anything so even if it were to miss there isn't a lot of gas to go out the tail pipe. And there also wouldn't be anything on top the engine to see as a leak.

BTW: At sea level on a 'standard' day the atmospheric pressure is 14.6960709 pounds/sq inch. Most people would call it 14.7 psi.

[Aloha66]

Hey Mr. Ivy66GT,
I think most people would call it between 14 and 15 psi just like Veronica noted. Civil Engineers would go with 14.7 but Electricals would run it out to 7 decimal points.

[66mustangx2]

Thanks for all the replies, I'll start checking and see what a I can figure out. The mountains are in the Northeast, some have a pretty good incline.

[66mustangx2]

Oh and by the way it just started last couple of cruise ins. I've had the car for 13 years never done this before on the mountains. See I live on the mountain and to go to car shows or cruise ins I have to go down and then back up to get home, most shows are on another mountain you'd just have to know the region

[Ivy66GT]

I guess I should have known that 7 digits might blow my cover.

Scottsboro, almost Chattanooga. OK, now I understand.

I agree, I have had my C-code '66 on some fairly steep mountain roads and never had anything similar happen.