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Just Some Dude in Jersey
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15,467 Posts
Discussion Starter · #1 ·
The previous owner of my car did a great job on a lot of the mods he did to the car, but some of his ideas were really stupid. I had to undo a few of them. One nice idea he did was to put a flush mount gas cap mod on the car. But then he cocked up the whole mod by RECESSING the flush mount cap 1" deep into the body with no drainage holes. A big 6" square recess, 1" deep, with a flush mount cap at the bottom. F'ing STUPID! If it rained I would have a 6"x6"x1" deep little swimming pool on my back deck. I had the body shop cut and fill the area with body putty. Around this time, one of our parts sellers told me "Some German guys have modded their cars to have the fuel filler neck stick out the back." Since I was going to put a wing on the car, this seemed like a pretty good idea. Plus, if German dudes do it, it's usually a pretty good mod. Bullschitt! I have yet to see anyone's GT with the fuel fill opening sticking out the back, leastwise a German dude's car.

It's been nothing but trouble. Fuel keeps backing up the filler neck or something else is happening and the fuel nozzle at the pump keeps turning off. I always have to pump every drop of fuel myself and fuel frequently gurgles out of the fill hole all over the car and the gas station's paving. I have tried and tried to reconfigure the filler neck for smoother flow and reconfigured my venting. I'm so sick of this problem that I'm about ready to cut another hole through the deck(and body putty and the remains of the recessed flush mount) and put the original filler neck system back in.

But I had a similar problem on my Ford Escape that I bought from my brother. Fuel would back up the filler neck and kick off the pump. He told me about this issue in advance. Well, an opelgt.com member turned out to work for Ford's customer complaint department and he said that he was given the job of fixing the 2003 Ford Escape fuel filling problem. Wow! What dumb luck! He sent me diagrams and stuff and said that the problem was caused by those yellow house spiders that make a little nest in the corners of the walls. They like the sweet smell of gas and the diameter of the vent hose is just the right size, so they climb inside and make a wispy nest. I followed his instructions and freed up the vent hose from the tank, the other end was open to the air, and tried to blow through it. No way, couldn't blow through it. I fished a wire through it and when it came out the other end there was a tiny bit of spider web on it. I could now blow through the hose easily and the problem was fixed! I wrapped a piece of window screen over the end and held it on with a wire tie and the car has gone 10 years without the problem recurring.

So, before I go nuclear and carve a 3" diameter hole in my car, I figured I would examine my venting. I had the filler neck and the rear driver's side vents connected together with a T-fitting and then the hose going above the tank to a convenient place to vent near my wheel wells. Okay, that looks good. Let's check the diameter of the outlet. Holy Schitt, my barbed fitting on the tank only had a 3/16" ID. The one on the filler neck is almost 5/16". Well, to make an already long story shorter, I decided to install a giant barbed fitting there. I had a fitting that was 5/16" ID, but decided to put the biggest one I could find in there, so I got a 3/8" one from the hardware store. I have a custom aluminum copy of a GT tank with NPT threaded openings, so it was a cinch to install. The OD of the 3/8" ID fitting was 1/2", so I used a big ole garden hose-sized vent hose. A petroleum friendly type. I put one of those filters that some guys install in their valve covers for pcv venting on the end. I won't know until I fill up again to see if the idea worked and fixed the problem.

Addendum:
Hooray! It worked! I had to put 3/4 of a tank of fuel in before going to a car show today and it filled all the way up with no pump kick offs! Hooray! Man, I feel like a dumb ass. I've been chasing this problem for almost 12+ years and here I find that the problem all along was that my vent outlets on my tank were too small, or I wasn't using enough of them, or I linked them all together in a closed loop, to let the air out of the tank fast enough when filling up. I figured that the filler neck was big enough to vent the air when filling up. I used the standard size tubing that fits the outlet on the filler neck, but that's a little sheet metal pipe with a larger inside diameter than the same sized barbed brass fitting I had on the tank. And I was only using the one rear vent on the tank, not the one in front. If I had been using both I might have vented enough, but I was only using one. It never dawned on me that venting of the tank was the cause of my problem. Oh well, if you chase a problem long enough you'll eventually fix it.

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Super Moderator
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13,943 Posts
It took me 12+ years to realize I’m an idiot
It took the rest of us substantially less time....
 

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Registered
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544 Posts
12 years huh?

Now you are ready for the 12 steps. Step one: Admitting everyone else has a problem.

Actually, I kind of like the relocated filler cap. Not enough to start hacking on a very original car, but it makes more sense to put it where yours is.
 

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Solo II is fun in a GT!
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430 Posts
So you are not thinking about moving your gas filler to behind one of the rear brake lights? Maybe you are not quite the idiot you hoped to be.
 

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Just Some Dude in Jersey
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15,467 Posts
Discussion Starter · #7 ·
Oh, and let's not forget the other tank venting clusterfluff I got into in 2016 when I was driving my GTX to the Opel Nationals for it's debut, with Norbert visiting from Germany following behind me in my Solstice. I filled up and we got 10 miles from my house when my engine shut down mysteriously, as though I had run out of gas. I brought a full tool kit with me and we field stripped the engine compartment looking for the problem. No luck. The car started up and I drove for another 2 miles and the car turned off again. The situation almost ruined Norbert's whole vacation to the U.S. and we would have had to get me towed home. At the last minute I recalled that I had an issue removing my gas cap before fill ups that previous week. I go to the back of the car and tried to remove the cap and it would barely turn and then a big suction sound happened when it finally came loose. The car started right up.

That was back when I had all 3 vents connected in a closed loop......no actual venting. I never had a problem with that, except for the tank filling issue, but the week before I had replaced my gas cap's ancient rubber gasket with a nice new grippy one from OGTS. That's when the suction sound when removing the gas cap started. So, once the car started after my breakdown, I pulled that gasket off and we were able to drive to Carlisle without incident.

Hilariously.....now....I ran out of gas at the top of one of the Delaware River bridges on the way home just 5 miles from my house and had to coast at 50mph down the bridge in heavy traffic, then do a radical, no engine power/no brake vacuum, rip through traffic jammed cars and traffic cones to the side of the road just before the toll booths with Norbert hanging with me like a professional rally car driver.

At about this same time, Charlie had installed a really powerful fuel injection pump and a new rubber gasket on his gas cap and he ALSO had close looped his vent lines. That high pressure pump and no venting/leaking at the gas cap caused his fuel tank to, as he put it, "coke can". The vacuum in the tank collapsed his Kadett's tank like a stepped on soda can.

Yup, me and fuel tank venting have a LONG history.

:)
 

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Opel Rallier since 1977
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2,278 Posts
LOL.... Even a standard, low pressure mechanical fuel pump can suck in a tank. My '62 Dart had the wrong type of cap put on it by the PO; it was a purge-only cap, but it had somehow been stuck in the open position. One day it decided to get unstuck and close up. < 2 miles down the road... FOOM! A big bang from the back. Sho 'nuff... the tank was sucked in.

My dad lost his gas cap on his '67 Dodge wagon back-in-the-day. and he put on a non-vented cap and ditto....KA-BOOM!
 

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Member
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1,722 Posts
Always remember where your open gas vents are when welding......
 
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