fuel tank questions

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4 speedin

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I need to purchase a new fuel tank, sending unit and original gas cap for my 68 Valiant build. I currently have a filler neck tube with a vent tube and had a aftermarket fuel cap. Debating on tube or no tube, Iv'e heard people talk about vented caps leaking fuel. Advise? Also is the spectra premium tank and sending unit the best bet for a quality restoration?
Any advise would be greatly appreciated.
 
I have a slightly used tank, sending unit and pad form my 69 Dart. Was on the car a few months and maybe three tanks full.

Let me know
 
4 speedin said:
I currently have a filler neck tube with a vent tube and had a aftermarket fuel cap. Debating on tube or no tube, Iv'e heard people talk about vented caps leaking fuel.
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I don't know where you folks get all this. Here is the deal:

ALL Mopars of the cars of which we speak used UNvented caps. The vent in the tube worked GREAT and has almost NO problems. Only troubles you might find with this is:

1....If "some bugs" (mud daubers, etc) made a mud plug in the tube with car parked long term, etc
2....If the tube rusts through or somehow gets damaged. Damage is rare, as it is fairly well protected
3....A VERY rare case might be you are in San Fran on the steepest hill you can imagine, parrallel parked with the cap down hill and the tank REALLY FULL on a HOT DAY. How rare is THAT!!!??? The vent might leak some fuel, which would drain "pretty much harmlessly" into and then out of the rear frame rail.

You want the factory VENT TUBE and you want a SEALED cap

Here is a screenshot of how this is laid out. This is right out of the factory manual The bottom of the tube ends INSIDE the rear frame rail

242yckm.jpg


This system was used up through 70 IN CALIFORNIA when CA started using the "new" carbon can/ evaporative emissions controlled. From 70--forward, several changes were made. For a couple of years, a vapor separator can was used in the trunk. Then, the separator was made inside the tank. In the following years there were SEVERAL changes in fuel caps known as "pressure / vacuum" caps. THESE CAPS ARE NOT VENTED in an operational sense. They contain a pressure and a vacuum pressure relief. So as vacuum or pressure builds, they will relieve.

THE OPERATIONAL VENT IN ALL OF THE EVAP CONTROLLED TANKS regardless of year was provided by the tube going all the way to the engine bay, for the evap/ carbon can system.
 
I bought a new tank and sending unit also. I was going to re-use the old filler neck tube, because it looked very good from the outside. But when I got it out, it was very badly rusted on the inside where it sits down in the tank. I ended up replacing the tube also.

BTW, I did buy a Spectra tank. Many people on this site recommended them.
 
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g413 said:
I bought a new tank and sending unit also. I was going to re-use the old filler neck tube, because it looked very good from the outside. But when I got it out, it was very badly rusted on the inside where it sits down in the tank. I ended up replacing the tube also.

BTW, I did buy a Spectra tank. Many people on this site recommended them.
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Thank you much for your help! Did you go with a vented tank and cap, Did you use the spectra sending unit also and did you have any leak issues. Just trying to get it right the first time. Mike
 
Thank you kindly for your explanation! So I don't need a vented tank or cap. The filler neck vent is all that's needed?
 
4 speedin said:
Thank you kindly for your explanation! So I don't need a vented tank or cap. The filler neck vent is all that's needed?
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You want a fill pipe with the vent tube and an un-vented gas cap. And the gas tank for a '68 has no evaporative-emission junk on it.
 
Guys, I see this posted sometimes, and there's a big factor here: OEM vs remakes/aftermarket on gas caps. Mopar caps from '70+ were partial-pressure caps, if you read the Allpar article it explains it better. The thing is those were only used on OEM caps. If you buy a remade cap/aftermarket cap those are all just vented caps. Way easier to remake them that way as that's whats readily available. Go investigate and see for yourself - even the primer exact replica caps are vented.

OP: Yes, get a new Spectra brand tank as those are very good quality. For a sending unit find an OEM or NOS one - all the aftermarket ones are garbage. If you're keeping your car original use the filler neck with vent tube attached. You may want to blow the vent tube out with compressed air to clean it and possibly add a small filter or screen underneath the car to insure it doesn't get crap in it over time.
 
kiss said:
Guys, I see this posted sometimes, and there's a big factor here: OEM vs remakes/aftermarket on gas caps. Mopar caps from '70+ were partial-pressure caps, if you read the Allpar article it explains it better. The thing is those were only used on OEM caps. If you buy a remade cap/aftermarket cap those are all just vented caps. Way easier to remake them that way as that's whats readily available. Go investigate and see for yourself - even the primer exact replica caps are vented.
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The exact-replacement gas cap for my '69 Dart that I bought from Year-One was not vented. So someone is making unvented caps. (And yes... Year-One is damn expensive)
 
69_340_GTS said:
The exact-replacement gas cap for my '69 Dart that I bought from Year-One was not vented. So someone is making unvented caps. (And yes... Year-One is damn expensive)
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I stand corrected then, there is an option, it will just cost you an arm and a leg. The caps you can get at the autoparts store, both locking and non locking, are vented. All the ebay remake ones are vented.

FWIW there's no functional problem having a vented cap on a '69 or earlier car.
 
So a new spectra premium tank (non vented) and sending unit it will be. And a non vented cap as well. I unfortunately through my original sender away including the lock ring. UGH
Thank you all very much for your advise! Much appreciated
 
4 speedin said:
So a new spectra premium tank (non vented) and sending unit it will be. And a non vented cap as well. I unfortunately through my original sender away including the lock ring. UGH
Thank you all very much for your advise! Much appreciated
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If you're going to use an aftermarket sending unit and lock ring be sure to check for leaks before installing the tank into the car. Also you'll want to look through the filler neck hole after installing the sending unit to be sure the pickup tube reaches all the way to the bottom.

Don't forget a filler neck grommet and a tank pad
 
kiss said:
If you're going to use an aftermarket sending unit and lock ring be sure to check for leaks before installing the tank into the car. Also you'll want to look through the filler neck hole after installing the sending unit to be sure the pickup tube reaches all the way to the bottom.

Don't forget a filler neck grommet and a tank pad
Click to expand...
Will do, Thank you much!
 
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