I have a 4th gen plastic fuel tank. Yesterday, I was filling up with gas, and when the gas pump stopped, fuel started spilling.
Background - engine swap and fuel tank mod was done by a local installer years ago. He seemed to be knowledgeable, but he combined the 4th gen tank & system with the 99 corvette fuel filter / regulator. I removed the regulator to get proper pressure.. That’s what’s changed. Would that cause any issues?

 

The fuel pressure regulator by itself shouldn't have any impact on fuel spillage. The act of removing the tank/pump probably has more to do with it. I would drop the tank down again and verify the large green oring that seals the pump is seated properly, supple, with no tears. Make sure the ring is locked fully. And while you're there, check to make sure none of the nipples on the pump body have any cracks. Gm pumps of that style are notorious for cracking at the fittings and causing leaks. It's probably our number 2 cause for evap small leak dtcs

 

Thanks - that does sound plausible.

 

Yep - the o-ring seal was missing. I must have forgotten the o-ring when I opened the tank last time. The tank is now sealed properly. No more issues. Thanks

 

Glad it was a relatively simple fix! Happy to help

 

I have the 4th gen tank in mine and I had a couple of unique issues. First, the float arm came off while I was driving and I had to drop the tank to reinstall and safety wire it to insure that it wouldn’t come off again. Second, after fixing the float, I started having the same issue with fuel overflowing during fill ups and sloshing out the top during spirited driving with one exception, I have center exhaust and it was spilling out on top of the pipes. I had to drop the tank again and found the roll-over anti-spill valve in the bottom of the tank. It is plastic and bonded to the top of the tank with a hose to the charcoal canister, but on the inside of the tank is the ball valve and cage that is snapped together, this is the part that I found in the bottom of the tank. It can’t be repaired and I didn’t want to compromise the tank by removing the top, so I plugged it at the hose nipple which permanently sealed it and I have not had an issue since. This is just something odd that I found with my 4th gen tank swap and I wanted to pass it along to the other members of this community. I’m also curious if anyone has had this happen to them?

 

Did you pull the gas tank or did a salvage yard?

 

The yard had pulled it, but I cleaned it and installed a new pump and module in it and drove the car 800 miles during shake down and another 300 after I completed the car before the float came off (that was from vibration). The anti-spill valve was intact at that point, the overflow issue began a few hundred miles later and I had to pull the tank a second time to fix that. This car is violent and I believe both issues were due to stiff suspension and the sound frequency of the exhaust (it literally shakes the ground and the buildings around it).

 

That's likely then. The plastic components on the tank are sonic welded, and vibration doesn't serve them well.

 

I was just passing along the experiences that I had with my 4th gen tank in. I have put a few of these in other 3rd gens without any of those issues, but it is something to be aware of with these tanks.