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The 72 "A" bodies had an emission standpipe for the gas tank. I am having a really strong fuel odor with the vehicle sitting in the garage. I traced it to the back from the gas tank.
For now, I want to stop the tank from venting until I can figure out what is going on. How do I seal the tank to prevent fuel vapors from coming out? Should I just seal off the 3 vapor lines from the top of the tank? (right, center and left vent line)
There should be no open vent lines on a 1972 Olds. The three lines connect to a separator under the rear seatback, and from there a single line runs to the charcoal canister under the hood. The system is (well, WAS) totally sealed from the factory. Are all these parts in place and connected properly?
There should be no open vent lines on a 1972 Olds. The three lines connect to a separator under the rear seatback, and from there a single line runs to the charcoal canister under the hood. The system is (well, WAS) totally sealed from the factory. Are all these parts in place and connected properly?
The 3 lines going to the standpipe in the seatback are connected but the charcoal canister is missing ALTHOUGH the lines running to the canister are capped off.
For now, I just want to get the gas tank sealed and figure out what's going on. Would it be OK to just seal/cap off the 3 vapor lines coming out of tank?
The 3 lines going to the standpipe in the seatback are connected but the charcoal canister is missing ALTHOUGH the lines running to the canister are capped off.
For now, I just want to get the gas tank sealed and figure out what's going on. Would it be OK to just seal/cap off the 3 vapor lines coming out of tank?
If you seal those lines, you will need to add a vented gas cap or else the engine will starve for fuel as the vacuum in the tank builds up.
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
The 72 came with a vented cap so that wouldn't be a big issue, unless of course someone replaced it with a non vented cap. I'll get a picture from the one on my car and post it here. I'm wondering IF the rubber hoses that vent the gas tank, and the rear canister are brittle or broken. That will also cause a gas smell through the trunk.
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
Here you go, note it has a double latch system on the cap, and the edges are extra deep for some reason. This cap is an OEM NOS part. I still have the original one the car came with.
I have the Duralast fuel cap # 6807 which is supposed to be "designed with proper pressure and vacuum relief but sealed to prevent evaporation of fuel"
The OEM vapor canister that was located inside the engine compartment on the passenger side area. One inlet port is for the vapor line coming from the gas tank to the vapor canister. What is the other input port for?
The canister has 2 ports.
Last edited by pettrix; June 9th, 2019 at 01:04 AM.
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
Ok, late to the conversation. This sounds like you have an aftermarket canister. What's this 3rd 'air' port you're talking about? Post a picture? There should only be 2 ports on a stock canister.
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
The picture shows something that's NOT a 1971/72 OEM part. I just continue to use the one that came with my car. That canister can be bypassed or plugged off it desired. The car will run without it.
The picture shows something that's NOT a 1971/72 OEM part. I just continue to use the one that came with my car. That canister can be bypassed or plugged off it desired. The car will run without it.
If you plugged off the vapor line. How would the gas tank purge the vapor? The 1972 tanks area sealed and the vapor has to go somewhere or it will cause fuel delivery issues. Or am I missing something?
To make sure I am not missing any lines. There are 3 lines that run from the gas tank to the standpipe that's behind the back seat. There is a 4th line that comes from the standpipe area that runs to the engine compartment vapor canister. There is the main fuel feed line that runs from the gas tank to the engine compartment.
Am I missing any lines? For a 1972 442 convertible. There wasn't a return fuel line from the engine compartment, right? I believe the F85's had a fuel return line but not the 2 door Cutlass.
If you plugged off the vapor line. How would the gas tank purge the vapor? The 1972 tanks area sealed and the vapor has to go somewhere or it will cause fuel delivery issues. Or am I missing something?
I plugged the vapor line at the canister on my car over 30 years ago and haven't had any issues.
I re-read your posts and you say you traced the fuel smell to the rear of the car. Since you are smelling fuel, there is obviously a leak, either liquid that is evaporating and not leaving a wet spot, or vapor that is escaping.
I saw this in another thread and thought it may be pertinent to your issue:
I bought a new tank as this one was close to 50 years old and I could smell gasoline in the back of the car. Seemed to me that the tank maybe had a pin hole somewhere or something like that. After pulling the tanks I found out that the filler neck where it goes into the tank was loose and there was fuel and fumes coming out of there.
I used compressed shop air to test the tank and lines for tightness. I would introduce shop air into a line and listen for hissing sounds. I found a couple of the factory styled spring clips were no longer tight at the rubber hose leading to the tank and had to remove and replace them with hose clamps that can be tightened. After replacing 3 of those, I retested and the tank held the air and the lines didn't leak.
My concern now is if I CAP the vapor line that goes to the vapor canister. What happens when you drive and fuel in the tank starts to drop. No new air is being introduced to the gas tank since it's sealed. Won't this cause a starvation problem due to vacuum building in the tank as fuel is used?
OK, good to know that you did a pressure test and things passed.
If you plug the vapor line then swap the gas cap to an earlier (1970 or older) cap, the system would be essentially the same as the pre-EVAP setups. I don't know what this may do for your odor issue, though.
Seems that if your tank and lines don't have leaks, the vapor canister is intact (no cracks/leaks) and has fresh charcoal, the hose from the canister to the carb is intact, and you have a factory closed air cleaner, there shouldn't be any gas smell. The system is fairly simple and not a lot of components. There has to be a leak that you haven't detected yet.
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
Just an observation on the tank factory spring clamps. Generally they don't have any issues. What does happen though is the rubber hose degrades over time (10-15 yrs depending on location) and that can cause the leaks. Fresh hoses and factory clamps should have held the fuel without any leaks. Mine didn't start leaking till they were close to 30 years old but I live in the land of snow and ice...
OK, good to know that you did a pressure test and things passed.
Seems that if your tank and lines don't have leaks, the vapor canister is intact (no cracks/leaks) and has fresh charcoal, the hose from the canister to the carb is intact, and you have a factory closed air cleaner, there shouldn't be any gas smell. The system is fairly simple and not a lot of components. There has to be a leak that you haven't detected yet.
I don't have a factory air cleaner. It's a K&N open element air cleaner.
Does the factory standpipe have any long term issues? I know fuel vapors enter the standpipe behind the seat, condense and return down the hose as fuel into the gas tank. If the standpipe leaked, I would assume it would lose air during my compressed air test.
The 1970 California cars had a three port canister. Just take the air port on the canister to the the air cleaner inlet, does not have to go to carb. and did not originally. Pictures in the CSM.
The 1970 California cars had a three port canister. Just take the air port on the canister to the the air cleaner inlet, does not have to go to carb. and did not originally. Pictures in the CSM.
The 70 air one goes to the throat or inlet of air cleaner, the extra one on a '70 ties into temperature controlled vacuum tee at front of engine. Must have decided they didn't need it for later cars.
August 7th, 2018, 09:13 AM
