As a warning for some of you who may be getting ready to do this. The job isn't difficult, just tedious, so please don't cut up your cars. However, the point of this thread is something to be carefull that you check first. When I got my new tank I checked it for measurement and fuel pump fit. I DID NOT CHECK THE GAS CAP AND THE STOCK ONE WILL NOT SCREW ON PERIOD! I see now that after some searching this is not uncommon! I mounted the tank in first and before I reinstalled exhaust rear end etc I wanted to pressurize the system to see if I had it all right an no leaks before assembling everything. This is when I found that the stock cap didn't fit. I bought a locking cap and I can get it to screw on but it is very difficult and results in multiple tries before the cap will stop leaking under a full tank-or releasing sickening fumes.

Just an FYI, quality of replacement parts in general seem to be really bad any more. By the way I bought it at Autozone, but I have had good luck with their stuff so far.

 

Thanks for the heads-up.

Fit quality from so-so to real poor seems to be the norm now that parts for older cars are made off-shore.

Outside door handles for W-Bodies is a good example. Lots of slop in the handle mechanism, the lock cylinders bind up when fastened to the handle assembly and the lock and latch rods need to be adjusted farther than what the factory designed in.

However, $35 shipped vs. $160 for OEM is the catch. For $125 difference, I'll live with the fit issues (just take a little bit more time to install) especially since the OEM handle doesn't last any longer than the cheap stuff before breaking.

 

Hmmm. I thought it was just something weird with my car. It had a gas smell near the tank and bought a new gas cap from Autozone to see if that was the problem. Even though I asked for a cap for an 85 Camaro, it wouldn't screw in. Fortunately, I transferred the new rubber O-ring to my old cap and that stopped the gas smell. I wondered if someone had changed out my gas tank, but maybe it's just the replacement parts not fitting.

 

I wound up having to use my bench grinder and remove a small amount of the height off of the threads on the cap. Little a time and it works now. The locking cap that is. The stock won't even come close. The punched in threads in the filler neck are visibly different on the stock tank versus the old.

 

88 bird fuel tank R and R i did a couple years ago out here


not that big of deal really

i dunno if yo them around on the site here but i have pics of doing this on the 88 bird

light baby blue one :P

 

I havent done a tank swap yet but i changed the fuel pump. It was easy sence i have no exhaust back there.

 

I replaced my tank also with a Spectre one. A stock gas cap does not fit on mine either. Ever since I put it in I have a small gas fume smell sometimes when I stop to park. I checked the valve back there and double checked all of my lines so I'm starting to think the gas cap vents a lot for some reason. The cap that fits mine fits 2nd gen cars. It's a locking one. Any input guys?

 

If you idle the car and then release the cap and you don't hear a hiss you do not have a seal. The threads on the cap in my case are too tall for lack of a better explanation. Read my post what I had to do. I tried two O-rings but that was pointless. One thing I noticed is that my neighbors late model Tahoe cap and my Suburban's cap would fit the new tank. These caps have what appears to be a pressure relief in them. Probably what engineers did to do away with our venting valve attached to our tanks. You might be able to make a new cap work. I would try a locking one first. If the tank holds pressure with either cap (our tanks are less than 1.5 lbs psi) then it works.

 

Do our tanks have a one piece filler neck welded to the tank? Mine leaks when I have a full tank and I need to fix it ASAP. Just haven't had a chance to crawl under there yet.

 

That was my unfortunate experience too, recently. The stock cap doesn't fit, why?????? I thought these were standardized? The filler neck doesn't line up correctly either. It's twisted a little to the left so my fuel door won't go on til I straighten it somehow. What a pain.

Paid $175 for the Spectra "premium" tank from rockauto. Tank was made in Canada. New sending unit/pickup for $125, also from Spectra but made in China. The Chinese sending unit is better than the $400 OEM part, not that they faced any real challenges in doing so.

 

Thanks for posting this. I have to do something about my tank and this is some pretty important info.

Product/Vendor review?

 

I should see if I can contact the previous owner of my car and see if he ever replaced the tank. My car had a Stant cap when I bought it 2 years ago that was not sealing well (leaking gas down the side of the car when driven), so I bought a new GM one that fit fine...for about a year. Last spring I had the same problem...the threads would not grab hold of the neck, and you could pull it straight off after trying to tighten it. It would taken 6-7 tries to get it on right. So off I went and bought 2 more GM caps. The current one fits just fine...we'll see how long it lasts.

I never had ANY problems with the GM caps on either my 89 RS or Formula, but both had OEM tanks. It sounds like mine may have been replaced then??

 

I had a problem with mine after I installed a new tank as well. The cap wouldn't fit so I filed the plastic threads down just a bit and now it fits better, but sometimes you have to play with it a bit to get it on. It does however seal just fine because it will hiss when i take the cap off. I bought my tank from Advance, it was made in Canada. It was either American Designer or Spectra Premium, can't remember.

 

I work at NAPA so tommorrow I'll give the tech line a call and see what I can find out. I'll post back after I talk to them.

 

That would be cool - I'd be very interested in what you hear.

 

I just got off the phone with a lady from Spectra. First of all everything I'm telling her she is repeating everything in French to another person she is on the phone with. So it takes them 10 mins to understand that the correct cap for the application does not fit. Finnaly she calls me back with a Stant # of 10819 that fits 2nd gen cars. That is what I already have that does not seal right. They then old me they do not know what to tell me. So I got no help at all. So I guess I'm gonna have to find a way to get it to seal right. Sorry I couldn't help.

Dave

 

I did the same thing and my stock cap will not fit. I can get it to start to go on but wont fully seat. The tank did come with a new cap and that fits fine. My filler neck was slightly off as well. I had to stick a long 1/2' extension down the opening of the neck and force the neck back. I heard a little crack which im asuming was part of the baffle that is in the end of the filler neck. I have not gone to the gas station yet to fill it up so I will see what happens.

 

Just came across this thread because I had the same issue. Replaced the gas tank, but didn’t know the threads were crap until it was too late. Best solution I could find was filing down the cap threads. However, I did come up with a repair that does not require you to drop the tank and ensures a trouble free cap. Use JB Weld Tank repair to install a weld-in motorcycle cap inside the filler neck. Worked perfectly and gives a custom touch. A couple of notes on the project

- the tank is Aluminum, so need to find an all aluminum cap assembly to prevent galvanic corrosion

- do not weld/braze to the tank if you have ever put gas in it. Stick with JB weld tank repair on this one so you don’t end up with a bigger mess.

- the cap I bought had a 1.75in OD that necked down to 1.5in OD. I bought this one: https://www.ebay.com/itm/Billet-Aluminum-Filler-Neck-Weld-On-Bung-Screw-Cap-Small-CNC-Gas-Oil-Tank-USA/ If you turned it upside down (Put large diameter into the filler neck), this would sit perfectly on top of the threads with a nice gap all the way around for JB weld (see first picture)

- I was worried the o ring would get torn up from not having a proper seating surface, and I wanted the cap to sit a little farther from the filler neck for easier access, so I added some scrap aluminum to make mine a constant 1.75in diameter and 0.125in longer. Then installed it “right side up” with JB weld.

There is an ideal weld in cap out there that has a 2in OD that necks down to 1.65in, but from everything I could find, the aluminum version has been discontinued.

I know this is too lake for those in this thread, but maybe it will help someone.

Weld in bung installed upside down.


Heated, bent, then brazed scrap aluminum to make constant 1.75in OD

JB weld assembly into place (right side up)

 

Thread is 12 years old. Proper fix is to use the late model cap the aftermarket tanks are designed to use.

https://www.thirdgen.org/forums/tech...termarket.html

Edit: Added link to more recent thread with easier fix.

 

yep, acknowledged the old thread at the start of the post. Maybe ask admin to delete it since it offered no resolution?

also saw the thread you reference. Gas cap depends on which tank you got in which year. Yes, finding a cap that fits is “easier”, but potentially longer process. Instead of buying a cap, waiting for processing/shipping, to find out I needed a different one, I went with the 100% fix that could be done in 1 day without question. No more guessing for me. 👍