Trying to find fuel leak

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AussieDart

AussieDart

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Hello,
I am hoping someone may have had the same problem that I have with my 69 Dart so they can tell me how to fix it.
On a recent trip it (273 V8) used half a tank of gas in an hour. This seemed rather excessive and also we noticed that there was the smell of gas in the car.
Obviously it has a gas leak somewhere. Got the car on a hoist and checked everything. Could not find any signs of a leak.
It has a new tank and sender and there are no leak stains.
I had some gas in a jerry can so I filled the car in my garage. The garage smelt like gas for quite a while. But once again there was no obvious sign of a leak and I did not start the car or have it running.
Any ideas you have would be appreciated.
Thanks, Ron.
 
Could be leaking at the fuel pump , line that runs from the pump to the carb or the carb itself
 
The obvious would be to start the car and see if you can find a leak in the lines. Especially on the pressurized side of the fuel pump. If nothing still, you might have a stuck needle in the carb. Propaply dumping gas down the intake. You can usually see the excessive gas going Into the venturi when the car is running/fuel pump is on. After you shut it down, the pressure from the fuel pump forces even more gas into the intake. Hence the smell. Pull a plug and see if you are running crazy rich (black plugs) I had an old chevy with a worn out quadrajet that did the same thing to me.
 
If there are no signs of an external leak, Check the fuel pump.

The diaphragm in the fuel pump maybe leaking fuel into the crankcase.

Pull the dipstick and check for thin oil and or the smell of gas.

Herb
 
With new tank and sender, I would bet on that, regardless of the lack of fuel stains. I've had erratic leaks from a poorly sealed tank sender, with smells and erratic poor gas mileage.
 
I love math. Lets see; drove for an hour; that would be about 60 miles at 60 mph. Ok used 1/2 tank; that would be 5 gallons. So 60 miles at 5 gallons. that would be 11mpg. So unless you have a potent big block, or a very potent small block, or race gears in the back,that is excessive. Its so excessive, that even a warmed over 360 would be acting like a pig.So, lets assume, for the moment that the gas is not going through the motor. That just leaves; into the motor or external.Since the OP says no signs of leakage, that just leaves into the motor. Theres only two ways into the motor.Through the carb or through the mechanical fuel pump.Since the OP didnt mention anything about how crappy it runs or idles, Id go with dart67 and the pump diaphram theory. But,here it comes, theres almost 3 gallons missing. If it was in the crankcase, the Op would have noticed the sluggish engine and likely the excessive exhaust smoke.
So,Im going with an external leak. And heres why; the OP did mention new tank and sender.And heres another but;I m guessing thats not relevant.It would be hard for me to imagine 3 gallons leaking out with no signs. Im thinking its leaking on the pressure side of the pump, while the engine is running.Then the airflow at 60 mph is taking it away. The smell when stopped is the last of it evaporating from a place you cant see.
Now theres only 2 places that you cant see; on top of the tank, and just below the fuel pump above the K. Since theres no fuel return on a 69 Dart 273,Above the tank is out. That leaves the area under the pump.
-So, my guess is the pump or lines or the little neoprene jumper is/are leaking, and dribbling down the top of the K and carried away by the airflow, and then evaporating when the engine is shut off. The most likely is the jumper.
-I urge you not to drive it until you fix the problem. Id hate to read that your car burned up. 2 to 3 gallons in 1 hour is a huge leak.It shouldnt be hard to find.
-It might also be that there are multiple keaks. eg. the sender may not be sealed either.Pull the dipstick. Check for stinky, runny,excessively high oil level. If its in the oil it will be coming out the tailpipe, stinky, too.
 
nm9stheham said:
With new tank and sender, I would bet on that, regardless of the lack of fuel stains. I've had erratic leaks from a poorly sealed tank sender, with smells and erratic poor gas mileage.
Click to expand...


Was the lock ring replaced on the fuel tank? The new ones are junk and too thin. They do not seal. You have to use the old lock ring....
 
The leak that stinks inside the car the most and shows the least evidence is the rubber ring gasket at the filler tube through tank. easiest way to prove the leak is there.. fill it to the brim. That route leads to a smelly, messy, repair though. To prove the leak isn't anywhere else with less than a full tank takes longer.
 
Hello Everyone, Thanks for the comments. They have given me some good starting points to get this fixed.
 
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