1971; How did Rain Water get in my Gas Tank?
 

My 71 ran beautiful till a few days after a huge rain storm the car wouldn't start. After getting my mechanic friend over here, we finally determined the problem was rain water (lots of it) in the gas tank.

It seems the water might have got in through the gas cap area. Isn't there a drain hole/ and tube there? Where is it? Can water build up on top of the gas tank and get in through the cap thats secured properly?
Also where is the gas tank vent on the 71 BB? Can it get in through there?
Thanks in advance. Steve

Most likely, the drain in the rubber boot around the gas tank neck is plugged. The water will sometimes get high enough to leak in through the gas cap, although I am not sure how. Or, there is a rust hole in the filler neck where the rubber boot is, and the water leaks in through the hole. Or, the gasket between the gas tank and the filler neck is shot, and water leaks in there.

Had a similar issue with my 72. After purging the tank and changing the fuel filter all was good, so figured it was some sort of weird occurrence as I couldn't figure out where it came from. Was thinking I got water in it as I fueled up in the rain.

Now jump forward almost 2 years... After rebuilding the motor I started to have carb issues due to the float and jets getting clogged with junk from my gas tank. Ultimately I dropped the tank this time and found I had a small hole about 3 inches above the filler neck. So got a new tank and all is good.

I had the same problem and my filler neck gasket was shot.

While you're inspecting your tank and gasket for where the water got in get a mechanics scope and see if the interior of your tank is rusted.

I had the same problem with my 96. plugged drain and rain filled the tank.

It seems to me the rubber boot is more a liability than an asset. The PO of my 75 removed it and I have no intention of replacing it unless someone here gives me a good reason I have not thought of.
I really dont think its a weather proofing issue.

Gonna pump the tank out. I'll take all your suggestions and keep you posted...

Just a WAG, but I think it is just the opposite of a weather proofing thing. The original rubber boot and drain tube would contain and drain any spilled gaqsoline out from around the filler neck. Without it, there is a good chance the gas could end up on hot mufflers, and then????????????

good point, I didnt think of that. :thumbs:

Pumped out the gas tank and added fresh gas. With some coaxing it started after the fuel line was purged too.
I think the car cover over the gas cap area formed like a water locked pressure "bubble" when it rained, possibly forcing the water in thru the cap area. I dont know how as the cap area appears tight and solid.

Can any of this area be inspected or taken apart w/o removal of the gas tank?

Also drain tube was blown out clean, however it appeared to be unblocked anyway.

Classic Vette in the rain.. :nono:
Car port or garage??

Your cap is probably not leaking. It's probably the filler neck to tank gasket that is deteriorated and leaking.

I have FIVE Vettes and 2 Garages... I'm looking to add another 2 garages this fall with a lift to store all 5.

Can that be inspected w/o removal of the tank?

Not really. You really can't see anything without dropping the tank and unbolting the neck. It's not a super hard job, but you may have to move the exhausts out of the way. Could be fun if everything is rusted up. Other than that, remove spare tire carrier, disconnect fuel lines, unbolt crossmember and straps, and the tank comes out the bottom. Drain the tank first and have a second person help with pulling and reinstalling the tank. It's a good time to replace any rubber lines and tank cushions. I had the same problem as you. I blew the mud dobber nest out of the drain hose and replaced the cap gasket, but it still leaked. Also, you may find the elusive tank sticker. I only had a 1/4" corner of mine left.

dropping the tank is not hard. It does not require the removal of anything other than the spare tire/tire pan. Then just unbolt the two straps if the tank is empty it can be pulled out painlessly in a hour taking your time. took the tank out of my buddys 69 vert a few weeks ago to have it blasted and recoated on the inside. the only prob we had was we put the new sending unit in before mount and broke it. put the tank in first then the sending unit. it is probly in need of a good cleaning and new strap pads due to its age anyway would be a good weekend project

Years ago my 71 was outside and covered in the rain. Same thing happened to me....twice! Hasn't happened since its never in the rain now. Always indoors since it was restored.

Ran the 71 around locally to test it after the rain-gas tank incident. It ran fine after some coaxing to start-up. No issues.
Its been sitting a couple days (untouched) and I went to start it and it cranked on the first turn of the key but didnt start, I pumped it a couple times, then the second turn; nothing. What happened? I have dash lights, stereo is playing, all interior lights are bright...:(
What happened? When I turn the key, I get nothing from under the hood...
Now what?:ack:

The tank does not have to be dropped to replace the gasket between the neck and tank. I replaced mine by removing the door, removing the rubber around the neck, it just pulls up over the neck and then removing the multiple bolts holding the neck to the tank.