Gas cap wont come off

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Steve Mcbean

Steve Mcbean

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I recently got the car back (71 Demon) from repair. Drove it about 15 miles days ago and today the gas cap wont turn and feels locked under pressure. Ots a cap with key. Key turns but cap is on tight. Tried channel locks but cap is shaped too roundly for grip and at an angle. Any advice?
 
Steve, in my world, there's no such thing as "won't come off". lol
 
Screenshot_2018-06-27-15-05-38-1.png
 
Just remove your gas line to relieve any pressure. At the tank or by the fuel pump.
 
Car hasn't run in a few days... there's no vacuum holding that cap on. And if it will run right now, beyond what the fuel bowl(s) hold, that'll confirm so !
 
Steve Mcbean said:
I agree brother. Just worried its under extreme pressure. Thinking of drilling a small hole to release pressure.
Click to expand...
I think that's perfectly acceptable. IF you decide to do that, fill the drill bit flutes with wheel bearing grease. That will suck the metal chips in like a magnet and keep them from falling into the tank. Works very well.
 
If you disconnect the fuel line from the carb it should relieve the suck & if that don't work I'd just drill a hole in the sumbitch, with grease as RRR said
 
If you get metal shavings in the filler neck, DO NOT TRY TO VACUUM THEM OUT WITH A SHOP VAC .
That all caps ×'s 10
 
How about some photos.

I doubt that there is either pressure or vacuume on the tank.

If the vent was blocked it would have stopped the flow of fuel long before you drive was over, or collapsed the tank.

And the only way to pressurize it would be if the vent was plugged and the gas heated up.

Most likely the internal locking mechanism is broken and the key is no longer able to retract the locking bars.

I don't know if your filler tube is installed from out side of the car or from the inside like 67-69 darts are.

If it is from the outside you could unscrew the seal from the trunk floor, and with some needle nose vise grips back out the 3 to 4 screws at the quarter panel that hold the filler neck to the quarter panel.

Or perhaps cut the screws off with a die grinder / Dremel and punch out the screws to the outside of the car.


If you have another locking gas cap like the one that is stuck on you could take it apart and find just where to drill or cut to remove the decorative part to access the workings.

Anyway use extreme caution, the vapors in the tank are not going to do anything till enough oxygen gets in. ( The sender is in the fumes and has exposed wires but can not cause a fire / explosion because there is not enough oxygen in the tank)
 
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Can you post a photo??? It’s the rubber gasket , wondering if you can get some WD40 with the bendable hose spout and spray at the underside of the cap and see if you can lube the gasket so it’s slips
 
The only idea I could think of if the WD-40 does not work is to clean the surface of the gas cap with abrasive cloth and get a half inch nut clean the surface of the nut get some JB Weld and JB Weld the nut onto the gas cap let it dry for 24 hours and then try to get a socket on the nut and see if some leverage with a ratchet may work and then try to lube it up at the same time

when I mean a half inch nut I mean a half-inch threaded nut so the outer surface of the nut would be like let’s say a three-quarter socket to get over the nut
 
If your tank is not venting you need to fix that. The evap controlled tanks all have a VENT that is the 1/4" line from rear to front. As said, try disconnecting the line(s)
 
Glenn’s HC said:
Can you post a photo??? It’s the rubber gasket , wondering if you can get some WD40 with the bendable hose spout and spray at the underside of the cap and see if you can lube the gasket so it’s slips
Click to expand...

BtW, that gas door was custom made.

20220103_223028.jpg


20220103_223015.jpg
 
Last thing.. are you turning the key the correct direction?

Seems like a dumb question but...


Something else to try.

Press in on the cap while turning the key.

Pull out on the gas cap while turning the key
 
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Dana67Dart said:
Last thing.. are you turning the key the correct direction?

Seems like a dumb question but...
Click to expand...

To the right. Wont turn to left. Its actually new and to remove, i wpuld turn key to right, apply some pushing pressure and turn to come off, but now that bastard wont turn at all.
 
Dana67Dart said:
Last thing.. are you turning the key the correct direction?

Seems like a dumb question but...


Something else to try.

Press in on the cap while turning the key.

Pull out on the gas cap while turning the key
Click to expand...

Wont even give pushing it in. Like its being sucked in by lots of pressure agaisnt the gasket. Someone else here mentioned there sgould be no pressure since i drove it days ago, but i ran it in the garage yesterday. Gonna try some other stuf some of you guys mentioned for tomorrow since its late now. I'll let u guys know how it went. Hopefully i dont create spark when i use my gas powered grinder on it...Lol...
 
Just trying to wrap my head around this- first, how your tank could develop enough "pressure" to lock your cap in place; the tank is vented, and even if the vent(s) plugged, you'd get vacuum, not pressure. Look at your tank, that kind of vacuum would be collapsing your tank.
If you did somehow get the tank pressurized to the point of not being able to remove the cap, it would be pushing fuel right out the carb vents and flooding everything out. And the pressure would not persist for days afterward.
It has to be a mechanical issue- the locking pawls are not releasing as the key is turned.
Get some penetrant sprayed into the lock, and behind the cap if possible. Keep working the key and the cap back and forth and you might get it to pop loose. Be patient and persistent. If not, you'll have to drill it out as others have described. Then get yourself a good standard cap.
 
..and like I said if it runs and will sit there running for any more than the fuel that the bowls hold, there is no vacuum sucking that cap on. No air in.. no fuel out!
 
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