Bad fuel leak
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
Bad fuel leak
Weird problem... when I fill up my 77, unless I drive a good 10 miles or so, it will absolutely DUMP fuel out of the passenger's side frame rail (approx area)
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Is your vapor canister up front still there and connected to the hard line no the frame?
Do you have a vented or sealed gas cap?
What might be happening is pressure is building up in the tank that may not be relieved via a vented gas cap or the vapor canister system. The extra pressure may be forcing the fuel through a loose or rotted fuel line on the passenger side. The two over there are the main line and the return line. The vapor canister line is on the driver's side.
The crappy part to all of this is you have to drop the tank to access any of these lines and that's a pain in the butt.
Do you have a vented or sealed gas cap?
What might be happening is pressure is building up in the tank that may not be relieved via a vented gas cap or the vapor canister system. The extra pressure may be forcing the fuel through a loose or rotted fuel line on the passenger side. The two over there are the main line and the return line. The vapor canister line is on the driver's side.
The crappy part to all of this is you have to drop the tank to access any of these lines and that's a pain in the butt.
Instructor
Joined: Nov 2005
Posts: 232
Likes: 0
From: Millersville Maryland
I just dropped my tank this summer and you have got to be sure to make those lines as tight as you can on the Right Hand side of the tank. The Left side is mostly for the Vapor Cannister and on mine (74) that stupid little "check valve" that sits up on top of the tank that you will NEVER be able to reach with out dropping it. This was actually thecause of my leak, Bubba thaought it wasn't neede and that chewing gum sealed a hole in the tank.
Last edited by Terrordome; Oct 15, 2007 at 07:30 PM.
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
Your car is a fire hazard and should not be driven until you solve the problem. Fuel is not coming from the frame, but a fuel line attached to the frame. The leak could be anywhere along the length and travel to the low spot located behind the front wheel and in front of the rear wheel. If the rubber lines are not the source, then the line just in front of the frame kick up seems to build the most rust. Gasoline fires are nasty and will do more than just claim your car. If you will be repairing the leak, disconnect your battery before getting under the car. A spark from a shorted circuit, or, can ruin your day.
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
I agree with everybody else drop the tank. Once you have siphoned the fuel out of the tank it is actually pretyy easy to remove. My 77 was leaking from the passengers side rear quarter panel running down in the muffler area. The rubber lines are probably deteriated. If you pop out the passengers side marker light you can look inside the area where the rubber lines run up into the tank. You will have a fuel line and aI guess they call it a vapor line.
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
Weird problem... when I fill up my 77, unless I drive a good 10 miles or so, it will absolutely DUMP fuel out of the passenger's side frame rail (approx area)
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
Rick B.
Advanced
Joined: Sep 2006
Posts: 78
Likes: 0
From: Nashville NC
Is your vapor canister up front still there and connected to the hard line no the frame?
Do you have a vented or sealed gas cap?
What might be happening is pressure is building up in the tank that may not be relieved via a vented gas cap or the vapor canister system. The extra pressure may be forcing the fuel through a loose or rotted fuel line on the passenger side. The two over there are the main line and the return line. The vapor canister line is on the driver's side.
The crappy part to all of this is you have to drop the tank to access any of these lines and that's a pain in the butt.
Do you have a vented or sealed gas cap?
What might be happening is pressure is building up in the tank that may not be relieved via a vented gas cap or the vapor canister system. The extra pressure may be forcing the fuel through a loose or rotted fuel line on the passenger side. The two over there are the main line and the return line. The vapor canister line is on the driver's side.
The crappy part to all of this is you have to drop the tank to access any of these lines and that's a pain in the butt.
Sounds like a venting problem, be sure to check ALL the lines & replace them if any are in question. It probably wouldn't hurt to replace them all at one time. I would use braided fuel line especially on the hard to get to lines just so they last longer. Just be careful to isolate them away from any electrical wires or connections to prevent a short. Also check all the steel lines by blowing through them with compressed air to clear out any debris & to see if any have rusted out. Would be useful to have a helper there to make it faster & easier. Also be sure to check the top of your fuel tank for rust through since they can hold moister up there & rot out. While you've got the tank out give it a coat of galvanized paint to prevent future rust problems. Worked for me.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Also, while you have the tank down, pull the tank shroud down and see if your tank sticker is still up there and in good shape. Just a bunch of perimeter bolts and the shroud can be wrestled down.Be very careful getting it down though because that paper is very delicate and if caught on anything it will rip.
Take pics and post if it's readable at all.
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
Weird problem... when I fill up my 77, unless I drive a good 10 miles or so, it will absolutely DUMP fuel out of the passenger's side frame rail (approx area)
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
here's the symptoms:
- Leaks 1-2 GALLONS (!!) of fuel if car is cut off right after fueling
- I am not topping off
- Fuel does not leak at all as long as motor's running
Anyone have any clues or prior experience with this? seems like maybe the overfill hose is ... bonkers... but i'm not over filling!
The leak isn't always where its dripping...could be traveling along the frame. Follow the wet back until you find a dry spot. trial and error. Recreate the events that cause it to leak. You will find it.
Hopefully its not the tank. The line is easy to repair.
Jim
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
Thanks for replies, a couple notes:
1. Duh, I know 2 gallons of explosive gas leaking out of the side of the car is a serious hazard
2. Gas cap is new locking type i bought from corvettecentral.com, need to return it though because the locking mechanism is broken. This might even be part of the problem.
3. Planning on dropping tank soon to replace, are there any larger tanks available? My mechanic said there was no space for anything bigger than whats in it.
1. Duh, I know 2 gallons of explosive gas leaking out of the side of the car is a serious hazard
2. Gas cap is new locking type i bought from corvettecentral.com, need to return it though because the locking mechanism is broken. This might even be part of the problem.
3. Planning on dropping tank soon to replace, are there any larger tanks available? My mechanic said there was no space for anything bigger than whats in it.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Aside from installing a higher capacity fuel cell there are no higher volume tanks available. However, I found that by doing away with the stock rubber bladder than you can get almost a full extra gallon...maybe more.
Make sure you get a gas cap based on your vapor canister system. Some of these cars have had their vapor canister removed. That system was also the pressure ventilation system so by capping that line they in effect make the system closed.
If the vapor system is removed and capped then a vented cap must be used to regulate the pressure. If you still have your stock vapor system in place you might look into it a bit and make sure you don't have any clogged lines or caps holding the pressure in the tank.
Make sure you get a gas cap based on your vapor canister system. Some of these cars have had their vapor canister removed. That system was also the pressure ventilation system so by capping that line they in effect make the system closed.
If the vapor system is removed and capped then a vented cap must be used to regulate the pressure. If you still have your stock vapor system in place you might look into it a bit and make sure you don't have any clogged lines or caps holding the pressure in the tank.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
got the word back from EB3, gas tank had a fist sized hole in the top of it. weird though that it didnt leak immediately when filling up, probably some sorta pressure factor, who knows, new tank and hoses on the way in
Melting Slicks
Joined: Jun 2005
Posts: 2,938
Likes: 2
From: Arkansas
I'm having the same issue as post #1 , here are the things that have changed since the problem started
1. Installed new gas tank....hoses looked good and clamped good
2. Hooked up my 1990 TPI charcoal canister and pressure valve just like the diagram
I also have a non-vented gas cap as well, but the plug that controls the charcoal canistor purge solenoid wasn't hooked up yet.
I'm thinking that the leak was from tank pressure after I cut the engine off and not being "relieved" by the charcoal canistor solenoid valve.
Would it be coming from the fuel vapor line hose on the passenger side? I'm thinking I might need to check that hose now.
1. Installed new gas tank....hoses looked good and clamped good
2. Hooked up my 1990 TPI charcoal canister and pressure valve just like the diagram
I also have a non-vented gas cap as well, but the plug that controls the charcoal canistor purge solenoid wasn't hooked up yet.
I'm thinking that the leak was from tank pressure after I cut the engine off and not being "relieved" by the charcoal canistor solenoid valve.
Would it be coming from the fuel vapor line hose on the passenger side? I'm thinking I might need to check that hose now.
Pro
Joined: Mar 2005
Posts: 683
Likes: 4
If the fuel is leaking at the point where the passenger door and the right rear tire I may have your answer. I have a 75 and a few years back I had that problem. The frame at the point I mentioned has a crossmember and a gusset of pretty good size at that area. The fuel line is located at this point also in this area called the kickup. What happens is dirt and grease will accumulate on top of the gusset and surronds the fuel line. When the dirt and grease gets wet or moist it will rust a small hole in the fuel line. If you need pics send me a PM. I fixed mine with a small length of rubber fuel line and used two clamps at each end for safety. Followed by surronding the fuel hose with a larger piece of hose to take care of any wear from vibration. You will not be able to replace the fuel line from the tank as it uaually requires the body to be lifted on that side to some point. Let us know how things work out.
Good Luck
Steve
Good Luck
Steve
Melting Slicks
Joined: Jun 2005
Posts: 2,938
Likes: 2
From: Arkansas
Thanks for the info and help Steve 
Actually it's leaking on top of the drivers muffler.....trickling down from the top of the gas tank.
I really think it's something to do with the pressure build-up because it does it when I stop the car and turn it off...like I said the tank pressure control valve I installed prior to do this may be the culprit.
Actually it's leaking on top of the drivers muffler.....trickling down from the top of the gas tank.
I really think it's something to do with the pressure build-up because it does it when I stop the car and turn it off...like I said the tank pressure control valve I installed prior to do this may be the culprit.
