Gas tank filler neck mystery

[popinsmoke]

Ok when I try to fuel my 67 Coronet 440 it will only take a half a gallon at a time then the fuel neck will fill and I will have to let the fuel drain from the neck into the tank and then fill another half gallon or so.

I am assuming that there is some obstruction of the filler neck causing it.

But I have another strange issue the other day and I parked the car and came out the fuel had crawled up the neck and started to dribble out the neck.

I started the car and after the car ran a few moments the fuel drained back in the tank?

The problem is compounded by the fact the gas gauge isn't functional.

I feel to get to the root of the problem I am going to have to drop the tank but where do I begin?

 

[terzmo]

I would check the vent tubes for blockage

 

[snakeoil24]

2x to terzmo

 

[shag766]

I would check the vent tubes for blockage

X2

 

[kb67mopar]

sounds like they have said on the vent tubes. To drop the tank drain it as best you can, disconnect the rubber hoses at the tank and then remove the j-bolt from the pass side frame and it will come down.

I have a used sending unit from a 66 coronet in excellent shape if you want for the fuel gauge issue. Just send me a PM

But basically if the vent is blocked then the filler is the only in/out besides the engine so as the fuel and vapor expands it will push liquid up the tube because of the way the filler sits in the fuel.

 

[440brew]

i had the exact same issue with my 67 coronet. it was definately the vent tube. as mentioned you will need to drop the tank. the vent has a 90 degree bend in the rubber hose and this is where mine was collapsed. while you are at it get a new vented cap. this is as important as fixing the tube. I got all parts at the local store for under 10 bucks. the rest is your easy labor... :grin:

 

[65 Plymouth Satellite 426]

X2!

 

[popinsmoke]

I disconnected the vent line at the 90 elbow at the bottom of the filler tube vent and blew it out first up the filler tube and no obstruction.

I then blew out the line that goes into the tank right above where the filler tube attaches to the fuel tank and was rewarded with the tank burping and puking gas on my head out the filler tube (I had the gas cap off).

So seems to me that air goes into the vent so it should be functional?

The car runs great without the gas cap on it states on the gas cap it is vented could the cap be bad?

Here is a link to my gas tank http://www.autopartswarehouse.com/d...acementQQFuel_TankQQ19661967QQREPD670103.html

I am not feeling very bright not being able to figure this one out.

Thanks in advance for any advice.​

 

[watermelon]

drain the tank and drop it. remove neck filler from car too. remove the sending unit from the tank and peek inside. if the tank has contamination/debris inside it might explain things. if you find anything it would be best to blow out old gas all the way up to the pump, replace fuel filters, and give the carb a good clean out.

the neck filler hardware is easy to inspect too.

i went through the gas system on my 1966 Coronet last year and cleaned it all out.

the hard part taking the gas tank in/out. you get good at it after doing it about 4-6 times like i did. :censored:

i found using a motorcycle jack with some plywood and foam on top provides a nice wide base to lift/lower the tank.


watemelon

 

[440brew]

try the gas cap first. this was part of my issue as noted above. the old cap I had said "vented" but is was not working. I repeated walked out to my coronet to find gas had pushed its way back up the filller neck. it has not happended since i dropped $5 on a new cap. try this before all the possible unnecessary labor.

 

[1969CoronetR/T]

I continue to have problems with my tank also. I got stopped on Friday for gas leaking out of the cap. I am not sure if it is my tank, filler neck or cap. Where do you buy vented gas caps?

 

[440brew]

I purchased mine a local Napa Auto Store. I believe any auto parts store should have them.

 

[Eddie Mopar]

Since you have tried clearing the vent line, I would tell you a couple of things that happen with these cars are normal. Please wait until I explain.
Since the gas pumps today force the gasoline out rapidly, the fuel does not always get a chance to settle quickly and foams right back out the filler neck. (Have you ever tried filling a glass of soda fast and see the results? )
Gasoline also has a tendence of expanding when the ambient temperatures rise into the 80's and 90's. The result is fuel spilling out the filler neck onto you paint. That last phenomenon is not something really new. When these cars where newer, they spit the fuel out over the quarter panel. Hence, when these cars were sold to the second/ third
owners, they most always had a dry paint etched in the quarter below the filler cap.

 

[1969CoronetR/T]

I replaced my cap and it seems to be working to stop the fuel from purging. I would check to see if your old caps rubber seal is worn as mine was stiff and apparently not making a good seal. The new cap is not vented and Auto Zone had it in stock. So far so good.