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Gas dripping on passenger muffler - found cause - post #12.
Kept smelling gas when returning from a ride...found that what looks like a large amount of liquid is dripping and staining the passenger muffler. I see a older rubber fuel hose about 1 foot long going between the gas tank outlet and the main metal fuel line above the muffler going to the front of the car. Does not look too hard to pull the clamps and hose off and replace if that is where the leak is.
Question is, if the car is not on will a large amount of gas come out of that gas tank fitting when I pull the hose off...will this be OK to try to do or do I have to drain the tank first somehow? Any other technique?
Thanks,
Redvette2
Passenger Muffler
Gas Tank Outlet and Hose.
Last edited by Redvette2; 10-24-2018 at 03:41 PM.
Reason: Updated title.
Yes, gas will come out as long as there is gas in the tank and the hose is off. The best thing to do is to disconnect it from the body line first and drain what's in the tank into a gas container granted it's not full.
I'd siphon as much gas out of the tank as possible.
One question I have- are you sure this line is leaking? If it is I'd think it would be dripping all the time as this is just a gravity feed point in the fuel delivery system at this location. The engine driven fuel pump bolted to the block is where the fuel pressure is increased to 5 - 7 psi for normal operation.
i had the same thing happen on my '72.
tank had rusted thru on the corner that sits on the frame mounts.
look into your tank thru the filler and see if it's rusty/pitted along the bottom edge..
Second photo looks like the tank is new. I disconnected the hose coming off the pickup tube and drained the gas into a five gallon bucket. Had vice grips handy to clamp off the hose if it had more than five gallons. Then I dropped the tank, replaced all rubber hoses and fuel separator. I feel good knowing all hoses are new and not going to leak.
That was the first issue I had when I bought my 76 3 years ago drove it home got up in the morning washed and waxed it came home later to find a bug puddle of gas right under the right muffler i droped the tank and replaced evey rubber hose from the tank to the carb as they are all the same age if one goes bad the rest are going soon
Yes, gas will come out as long as there is gas in the tank and the hose is off. The best thing to do is to disconnect it from the body line first and drain what's in the tank into a gas container granted it's not full.
I'd siphon as much gas out of the tank as possible.
One question I have- are you sure this line is leaking? If it is I'd think it would be dripping all the time as this is just a gravity feed point in the fuel delivery system at this location. The engine driven fuel pump bolted to the block is where the fuel pressure is increased to 5 - 7 psi for normal operation.
No...not sure this is where it is leaking as I could not find any wet spots (after a few days). The tank is new and the area that the muffler sees the most staining is on the top middle area. I do not see any leakage from the outlet area or the hose shown in the second picture. The issue happens after a drive and the smell goes away in a few days. I did fill the tank very carefully last time to what I thought was reasonable full. Also have a new vented gas cap installed.
I will take a closer look tomorrow and try to run the car for a short while with the wheel assembly off and see if I can find something. I will also look at the AIM and where the vapor return line is located and the also overflow's location. Thanks for everyone's suggestions.
Vapor valve is located on the top front drivers side corner of the gas tank (at least on my '71, should be the same on '72 I would think). I also think your '72 should have a sealed gas system meaning no vented cap. I'm not sure when Chevy went to a vented gas cap but I don't think it was in '72.
This is what the vapor separator looks like:
It bolts to the bracket shown in this picture:
My car is actually a 1968 and the AIM shows the fuel line on the passenger side. Also I can see two lines running down the passenger side together (one small and one large) so they likely changed locations since then. Looking at the outlet in the drawing it looks like my newer tank is aftermarket and does not have the stock location (outlet on mine is on the bottom passenger side of the tank).
I will check this all out tomorrow.
Thanks again,
Redvette2
1968 AIM Fuel and Exhaust Drawing
Another AIM drawing...this is like my setup.
Last edited by Redvette2; 10-23-2018 at 11:35 PM.
Reason: Added second drawing.
I gotcha. I don't think the ECC was on '68's. I think it started in 1970 so you would only have the fuel delivery lines and probably a vented fuel cap.
Inspected the area around the tank and found this hose assembly just setting in loose on the passenger side. Suspect this is item 10 in picture two above which is the fuel return hose going to the top of the tank. If nothing hooked up to the tank there perhaps gas is sloshing around and coming out the connection (Edit: or just the gas coming out at the end of the damaged fuel line). Will investigate further later today and report any findings.
Redvette2
Likely a vapor line return hose. Edit: Nope...fuel return line.
Last edited by Redvette2; 10-27-2018 at 05:23 AM.
Reason: Second idea added...corrected line type.
Yep that was it....broken fuel return line and nothing attached to the inlet at the top of the tank. Top of the tank area around the inlet is clean but the area where the metal line ends looks like it was leaking and causing this issue. Good news is that the access to the top of the tank for the fitting is open and easy to get to. Bad news of course is that this metal line is in pretty bad shape. I will try to patch the line to tank connection to at least temporarily stop the flow but long term I will replace the whole line back to the fuel pump.
Thanks again for everyone's input.
Redvette2
Edit update: Took off about 1" of the remaining metal line and found that the steel was still in good shape. Connected with new 1/4 inch fuel hose and clamps to the inlet of the tank. Took a run and no more gas smell. Bought several sizes of fuel and vacuum hoses to start on replacing everywhere they are needed.
Last edited by Redvette2; 10-27-2018 at 05:26 AM.
Reason: Added temporary fix and results. Corrected line type.
You found the cause of your immediate problem...but you also identified an "area of concern": the old and degrading rubber hoses on your fuel tank.
If these hoses are 40+ years old (), they NEED to be replaced. And, if they are accessible, you can change them easily if you have the proper sizes of rubber fuel lines, some new retaining clamps, and two strong [hand] squeeze clamps or flat-jawed Vise-grips. Clamp off the old hose near the point of fuel incoming fuel; remove the other end from hard line; install the replacement line onto that hard line; put clamp on the other end of the new hose in preparation of installing it. Now for a little "sleight of hand": Remove the clamp from the tank-end of the hose (or move it back to free the hose) and with one hand on the hose at the tank outlet fitting and the other hand holding the end of the new hose, pull off the old hose and immediately install the new one. If you do this well, there will be VERY LITTLE loss of fuel and you won't need to drain the fuel tank.
Put a pan underneath to catch any spillage; turn off any open flames in the area where you will be working; and have a fire extinguisher at-hand 'just in case'. You won't need the extinguisher, but "better safe than sorry". If you have all the materials you need to do all the old hoses on the tank, you can use this process and have them all done in less than one hour! You will most likely only need one hand clamp for this process; but in the off chance that you feel you need to seal off BOTH connections for one hose, you can expand the process to put a sealing clamp on the old AND the new hose sections, and do that little magic act for both ends of that hose.
You found the cause of your immediate problem...but you also identified an "area of concern": the old and degrading rubber hoses on your fuel tank.
If these hoses are 40+ years old (), they NEED to be replaced. And, if they are accessible, you can change them easily if you have the proper sizes of rubber fuel lines, some new retaining clamps, and two strong [hand] squeeze clamps or flat-jawed Vise-grips. Clamp off the old hose near the point of fuel incoming fuel; remove the other end from hard line; install the replacement line onto that hard line; put clamp on the other end of the new hose in preparation of installing it. Now for a little "sleight of hand": Remove the clamp from the tank-end of the hose (or move it back to free the hose) and with one hand on the hose at the tank outlet fitting and the other hand holding the end of the new hose, pull off the old hose and immediately install the new one. If you do this well, there will be VERY LITTLE loss of fuel and you won't need to drain the fuel tank.
Put a pan underneath to catch any spillage; turn off any open flames in the area where you will be working; and have a fire extinguisher at-hand 'just in case'. You won't need the extinguisher, but "better safe than sorry". If you have all the materials you need to do all the old hoses on the tank, you can use this process and have them all done in less than one hour! You will most likely only need one hand clamp for this process; but in the off chance that you feel you need to seal off BOTH connections for one hose, you can expand the process to put a sealing clamp on the old AND the new hose sections, and do that little magic act for both ends of that hose.
Thanks...this car is a on-going hobby for me and any repair assistance and information is greatly appreciated. This is a new old car to me and safety and reliability are definitely my first priority. The previous owner (s) did replace a lot of stuff and there are lots of new parts already on the car but right now it seems like each time I fix something another thing pops up. However I really enjoy working on it. I keep reminding myself that it is 50 years old!
Just to clarify so those who read this may not realize that the line you repaired on the passenger side of the car is NOT the vapor line. It is the fuel return line.
The vapor line was installed on the drivers side of the car on those Corvettes that required it.
Just to clarify so those who read this may not realize that the line you repaired on the passenger side of the car is NOT the vapor line. It is the fuel return line.
The vapor line was installed on the drivers side of the car on those Corvettes that required it.
DUB
Got it...makes sense why the later model drawing was different and so much gas was coming out of this line. Fuel return line is when excess fuel from the mechanical fuel pump needs to be disposed of?
Got it...makes sense why the later model drawing was different and so much gas was coming out of this line. Fuel return line is when excess fuel from the mechanical fuel pump needs to be disposed of?
Redvette2
Correct. The fuel return line is allowing all unneeded fuel that the fuel pump is pumping is going back to the fuel tank.
Correct. The fuel return line is allowing all unneeded fuel that the fuel pump is pumping is going back to the fuel tank.
DUB
Thanks. I think I know why some of us are confused...look at post #9, second AIM picture for my 1968 car. The item 10 hose I fixed is identified as a "FUEL VAPOR RETURN LINE".
Thanks. I think I know why some of us are confused...look at post #9, second AIM picture for my 1968 car. The item 10 hose I fixed is identified as a "FUEL VAPOR RETURN LINE".
Redvette2
YES. It is written that way as I can clearly see.
But....the fuel that is retuning back to the tank is not a vapor... but rather a liquid. As you also know.
Just goes to show you that sometimes things are not correct in these manuals in regards to how things were written. Heck we are all human and the proof reader missed that one.
I am sorry to comment on this the way I did even though you were only repeating what you read in written text. So I did not mean to offend you. if I did.
But regardless of that. There is no way in heck anyone can convince me that the fuel return line is a vapor line just because GM wrote it that way. As you know...It all boils down to basic chemistry. A solid...a liquid or a gas or vapor.
As I mentioned I one of my recent posts. It was just to clarify this error so people do not call it what it was being labeled as. And not understand why it was labeled incorrectly. Was just trying to inform so people know what this is called if they need to talk about it. Because if people say that their 'vapor line ' is leaking fuel. I would think it is the real vapor line on the left side of the car and they would have a SERIOUS problem if that were the case.
So...unless for some strange design inside the mechanical fuel pump that I am not aware of.. The liquid fuel is miraculously converted into a vapor the instant it enters into this line and then while traveling back to the fuel tank it condenses back into a liquid and thus can leak onto a muffler. Which I fell we all know is not the case at all. But IF it were...then I guess you could call it a vapor line....but I seriously doubt it.
But....the fuel that is retuning back to the tank is not a vapor... but rather a liquid. As you also know.
Just goes to show you that sometimes things are not correct in these manuals in regards to how things were written. Heck we are all human and the proof reader missed that one.
I am sorry to comment on this the way I did even though you were only repeating what you read in written text. So I did not mean to offend you. if I did.
But regardless of that. There is no way in heck anyone can convince me that the fuel return line is a vapor line just because GM wrote it that way. As you know...It all boils down to basic chemistry. A solid...a liquid or a gas or vapor.
As I mentioned I one of my recent posts. It was just to clarify this error so people do not call it what it was being labeled as. And not understand why it was labeled incorrectly. Was just trying to inform so people know what this is called if they need to talk about it. Because if people say that their 'vapor line ' is leaking fuel. I would think it is the real vapor line on the left side of the car and they would have a SERIOUS problem if that were the case.
So...unless for some strange design inside the mechanical fuel pump that I am not aware of.. The liquid fuel is miraculously converted into a vapor the instant it enters into this line and then while traveling back to the fuel tank it condenses back into a liquid and thus can leak onto a muffler. Which I fell we all know is not the case at all. But IF it were...then I guess you could call it a vapor line....but I seriously doubt it.
Sorry for all of the blah, blah, blah.
DUB
DUB
No worries...not offended at all. We all are just trying to understand how our cars work so we can properly take care of them. Perhaps because this is a lower pressure line, they thought some of the gas would turn to vapor or its meaning was a bit different back then before emission reg's came along. After all I heard people use to get the "vapors" as a physical condition back in the turn of the previous century.
10-23-2018, 06:49 PM
Gas dripping on passenger muffler - found cause - post #12.
), they NEED to be replaced. And, if they are accessible, you can change them easily if you have the proper sizes of rubber fuel lines, some new retaining clamps, and two strong [hand] squeeze clamps or flat-jawed Vise-grips. Clamp off the old hose near the point of fuel incoming fuel; remove the other end from hard line; install the replacement line onto that hard line; put clamp on the other end of the new hose in preparation of installing it. Now for a little "sleight of hand": Remove the clamp from the tank-end of the hose (or move it back to free the hose) and with one hand on the hose at the tank outlet fitting and the other hand holding the end of the new hose, pull off the old hose and immediately install the new one. If you do this well, there will be VERY LITTLE loss of fuel and you won't need to drain the fuel tank.
The fuel return line is allowing all unneeded fuel that the fuel pump is pumping is going back to the fuel tank.