Draining/cleaning/flushing C3 fuel tank
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,282
From: Central Maryland
Draining/cleaning/flushing C3 fuel tank
Hi all,
C4 guy needs C3 advice (model year 1981):
What's it take to resolve fuel tank issues (sediment accumulation, etc)? Is this something that can be dealt with on-car, or does the tank need to come out?
If the tank needs to be yanked, what's involved with that?
Many thanks in advance for any insights.
Be well,
SJW
C4 guy needs C3 advice (model year 1981):
What's it take to resolve fuel tank issues (sediment accumulation, etc)? Is this something that can be dealt with on-car, or does the tank need to come out?
If the tank needs to be yanked, what's involved with that?
Many thanks in advance for any insights.
Be well,
SJW
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
junk in the tank generally requires pulling the tank to clean it up. Could be the inside of the tank is disolving, would mean a new tank. There are also products out there to line the tank with, also means removing the tank.
Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
Likes: 3,865
From: Palm Springs, CA.
Save yourself the grief and time and just buy a new one off eBay for less than $200. nothing worse than having to pull the tank a second time 'cause the rust/crud is coming back and plugging fuel filter every two days.
Best,
Greg
Burning Brakes
Joined: Jan 2006
Posts: 1,154
Likes: 1
From: St Augustine FL
I have an 82 and I cleaned my tank as per the shop manual. The 78-82 vettes have a tank with a liner/bladder. Replacement tanks are not manufactured. If you replace the tank you will have to find a used one and they are expensive $200-400 depending upon how greedy the seller is.
The shop manual instructions are as follows:
Disconnect the battery ground.
Remove the gas lid assembly and rubber boot.
Remove the sending unit throught the fuel door hole.
Drain the tank. I used a syphon and a big sponge.
Use a Damp rag and or sponge and wipe the inside of the tank clean rinsing the rag or sponge frequently. Repeat as many times as needed to remove gunk and sediment.
Replace the fuel sock on the sending unit.
Then reinstall in reverse order of disassembly.
You do not have to remove the tank.
Good luck it takes about an hour.
The shop manual instructions are as follows:
Disconnect the battery ground.
Remove the gas lid assembly and rubber boot.
Remove the sending unit throught the fuel door hole.
Drain the tank. I used a syphon and a big sponge.
Use a Damp rag and or sponge and wipe the inside of the tank clean rinsing the rag or sponge frequently. Repeat as many times as needed to remove gunk and sediment.
Replace the fuel sock on the sending unit.
Then reinstall in reverse order of disassembly.
You do not have to remove the tank.
Good luck it takes about an hour.
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
I've yanked the tank on my '81 (twice 
) & there's really not a lot to it. The worst part was connecting/disconnecting the lines at the top & not letting it then snowball into a general R&R of all the parts back there! I syphoned the gas out to make it a lot lighter, which is well worth doing, as it's surprising how much gas is in there when the gauge reads empty. I'd suggest getting new anti squeek rubbers prior to removing it as you'll probably find the originals fall apart (I used some roof felt). Place some old carpet, or something soft, under there to drop the tank down onto. If you drop it onto a hard floor then it only takes a small piece if grit to puncture the underside, particularly if there's internal corrosion. You need to remove the spare wheel & tub & then you should be able to drop the tank down once you've removed the straps, etc. I managed it without having to remove the mufflers, but it was quite tight doing it. One thing I should have done is got some help at the points where I was dropping & raising the tank. It's not heavy, but it is awkward when you're under it. Plus having somebody hold it up will probably make it easier to refit all the hose connections 
I also cleaned it up & painted it with the zinc gas tank paint & it still looks good a few years later.
I'd be interested in whether your tank has a liner in it as mine didn't.
Good luck
Thanks for the tip on Quanta. I didn't think tanks were being made for the '81?
) & there's really not a lot to it. The worst part was connecting/disconnecting the lines at the top & not letting it then snowball into a general R&R of all the parts back there! I syphoned the gas out to make it a lot lighter, which is well worth doing, as it's surprising how much gas is in there when the gauge reads empty. I'd suggest getting new anti squeek rubbers prior to removing it as you'll probably find the originals fall apart (I used some roof felt). Place some old carpet, or something soft, under there to drop the tank down onto. If you drop it onto a hard floor then it only takes a small piece if grit to puncture the underside, particularly if there's internal corrosion. You need to remove the spare wheel & tub & then you should be able to drop the tank down once you've removed the straps, etc. I managed it without having to remove the mufflers, but it was quite tight doing it. One thing I should have done is got some help at the points where I was dropping & raising the tank. It's not heavy, but it is awkward when you're under it. Plus having somebody hold it up will probably make it easier to refit all the hose connections I also cleaned it up & painted it with the zinc gas tank paint & it still looks good a few years later.I'd be interested in whether your tank has a liner in it as mine didn't.
Good luck
Thanks for the tip on Quanta. I didn't think tanks were being made for the '81?
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
I am sorry as I was wrong. I just checked with Quanta about the fuel tank and was informed the newest tank they have is for the 1977 Corvette.
From what BlueSilver82 posted I hope you will be able to clean your tank. And use a good inline fuel filter.
From what BlueSilver82 posted I hope you will be able to clean your tank. And use a good inline fuel filter.
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,282
From: Central Maryland
Originally Posted by bluesilver82
I have an 82 and I cleaned my tank as per the shop manual. The 78-82 vettes have a tank with a liner/bladder. Replacement tanks are not manufactured. If you replace the tank you will have to find a used one and they are expensive $200-400 depending upon how greedy the seller is.
The shop manual instructions are as follows:
Disconnect the battery ground.
Remove the gas lid assembly and rubber boot.
Remove the sending unit throught the fuel door hole.
Drain the tank. I used a syphon and a big sponge.
Use a Damp rag and or sponge and wipe the inside of the tank clean rinsing the rag or sponge frequently. Repeat as many times as needed to remove gunk and sediment.
Replace the fuel sock on the sending unit.
Then reinstall in reverse order of disassembly.
You do not have to remove the tank.
Good luck it takes about an hour.
The shop manual instructions are as follows:
Disconnect the battery ground.
Remove the gas lid assembly and rubber boot.
Remove the sending unit throught the fuel door hole.
Drain the tank. I used a syphon and a big sponge.
Use a Damp rag and or sponge and wipe the inside of the tank clean rinsing the rag or sponge frequently. Repeat as many times as needed to remove gunk and sediment.
Replace the fuel sock on the sending unit.
Then reinstall in reverse order of disassembly.
You do not have to remove the tank.
Good luck it takes about an hour.
Thanks again.
Be well,
SJW
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Thread Starter
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,282
From: Central Maryland
Originally Posted by UKPaul
I've yanked the tank on my '81 (twice ) & there's really not a lot to it. The worst part was connecting/disconnecting the lines at the top & not letting it then snowball into a general R&R of all the parts back there! I syphoned the gas out to make it a lot lighter, which is well worth doing, as it's surprising how much gas is in there when the gauge reads empty. I'd suggest getting new anti squeek rubbers prior to removing it as you'll probably find the originals fall apart (I used some roof felt). Place some old carpet, or something soft, under there to drop the tank down onto. If you drop it onto a hard floor then it only takes a small piece if grit to puncture the underside, particularly if there's internal corrosion. You need to remove the spare wheel & tub & then you should be able to drop the tank down once you've removed the straps, etc. I managed it without having to remove the mufflers, but it was quite tight doing it. One thing I should have done is got some help at the points where I was dropping & raising the tank. It's not heavy, but it is awkward when you're under it. Plus having somebody hold it up will probably make it easier to refit all the hose connections I also cleaned it up & painted it with the zinc gas tank paint & it still looks good a few years later.
I'd be interested in whether your tank has a liner in it as mine didn't.
Good luck
Thanks for the tip on Quanta. I didn't think tanks were being made for the '81?
) & there's really not a lot to it. The worst part was connecting/disconnecting the lines at the top & not letting it then snowball into a general R&R of all the parts back there! I syphoned the gas out to make it a lot lighter, which is well worth doing, as it's surprising how much gas is in there when the gauge reads empty. I'd suggest getting new anti squeek rubbers prior to removing it as you'll probably find the originals fall apart (I used some roof felt). Place some old carpet, or something soft, under there to drop the tank down onto. If you drop it onto a hard floor then it only takes a small piece if grit to puncture the underside, particularly if there's internal corrosion. You need to remove the spare wheel & tub & then you should be able to drop the tank down once you've removed the straps, etc. I managed it without having to remove the mufflers, but it was quite tight doing it. One thing I should have done is got some help at the points where I was dropping & raising the tank. It's not heavy, but it is awkward when you're under it. Plus having somebody hold it up will probably make it easier to refit all the hose connections I also cleaned it up & painted it with the zinc gas tank paint & it still looks good a few years later.I'd be interested in whether your tank has a liner in it as mine didn't.
Good luck
Thanks for the tip on Quanta. I didn't think tanks were being made for the '81?
Be well,
SJW
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
Originally Posted by SHAKERATTLEROLL
I am sorry as I was wrong. I just checked with Quanta about the fuel tank and was informed the newest tank they have is for the 1977 Corvette.
).Dirt/rust/debris in fuel tanks can cause untold problems with fuel systems (carb flooding being a favorite). I once had to sort out a bike that was suffering from this & it was surprising how much crud there was in just one small tank. No matter how much I washed it out, there was always more fine rust that eventually worked loose & found it's way into the carb (even after the old trick of putting ball bearings in the tank & giving it a good shake). I had to resort to coating the inside with Petseal to seal it all up in the end. This would be very expensive in a tank the size of a Vettes, but Fedx told me that there something called MarineTex (Marinetec?) available for fuel tanks for boats that does the same thing & is is a lot cheaper.
