74 Fuel Leak
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
74 Fuel Leak
Alright I know this isn't the greatest pic but I just recently got the car and I need two more jack stands. Fuel on the floor after starting and then hitting the accelerator. You can see what I took a pic of is wet. What am I looking at and what's the likely culprit? Let me know if you need to know anything else and thank!
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
This is driver side which is where fuel lines are shown in my repair manual? Yes I have a repair manual but I thought I would ask experts first.
Team Owner
Joined: Sep 2006
Posts: 31,274
Likes: 4,366
From: Westminster Maryland
Hi A,
The fuel supply and return run along the passenger's side frame rail.
The fuel vapor line runs along the driver's side frame rail.
Your picture 'appears' to be of the forward area of the driver's side foot well with the transmission beyond…. the center of the car.
Really the only way fuel can get to that point is by dripping off the rear of the intake manifold near the distributor and running down onto the transmission linkage. That maybe where it's dripping, but it's source is elsewhere.
No fuel lines in that area unless someone has done an owner inspired modification.
What manual are you looking at?
Regards,
Alan
The fuel supply and return run along the passenger's side frame rail.
The fuel vapor line runs along the driver's side frame rail.
Your picture 'appears' to be of the forward area of the driver's side foot well with the transmission beyond…. the center of the car.
Really the only way fuel can get to that point is by dripping off the rear of the intake manifold near the distributor and running down onto the transmission linkage. That maybe where it's dripping, but it's source is elsewhere.
No fuel lines in that area unless someone has done an owner inspired modification.
What manual are you looking at?
Regards,
Alan
Last edited by Alan 71; Nov 30, 2014 at 06:25 PM.
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
As Alan said - there shouldn't be any fuel lines in that area. I would check the area on top of the engine. The carburetor would be a likely suspect. The fuel line (on an original car) should be coming up from the pump on the passenger side front of the engine, and entering the carb. What you are showing is likely a leak running down into that area.
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
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From: Quincy IL
Lol its a Haynes and now I see where it says vapor I'm sorry. This is the oldest vehicle I've owned and the first I've worked on with a fuel leak. I really appreciate the help and I'm glad i asked!
Le Mans Master
Joined: Aug 2006
Posts: 7,426
Likes: 1,559
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Your correct, the vapor recovery line starts at the left side of the tank, it connects to one side of the vapor canister, the other port on the vapor canister connects to the carburetor.
There is a vapor separator attached to the tank. When working properly it lets fumes from the tank go to the vapor canister but it will stop raw gas from entering the line.
Any chance that you topped up the tank and parked with the left side of the car facing down?
There is a vapor separator attached to the tank. When working properly it lets fumes from the tank go to the vapor canister but it will stop raw gas from entering the line.
Any chance that you topped up the tank and parked with the left side of the car facing down?
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
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From: Quincy IL
I did too the tank off with premium and stabil for winter storage. But based on the marks on my garage floor which is level it happens every time I start it and hit the accelerator. Specifically today I went out, started it, looked under the car nothing, got in and revved the engine, looked again and there was gas on the floor. Thanks.
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Le Mans Master
Joined: Aug 2006
Posts: 7,426
Likes: 1,559
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
You do have a fire extinguisher handy, right!
The fuel pump is on the right side near the front/bottom of the engine.
Two hard lines connect from the tank to the fuel pump with rubber lines.
One is the feed to the carburetor the smaller is the fuel return line.
Check those rubber lines.
Two hard lines connect from the tank to the fuel pump with rubber lines.
One is the feed to the carburetor the smaller is the fuel return line.
Check those rubber lines.
Team Owner
Joined: Sep 2006
Posts: 31,274
Likes: 4,366
From: Westminster Maryland
Hi A,
While the Haynes manual is o.k. in a pinch, there's a much better resource available for not too much money.
It's the GM Chassis Service Manual. There's one available for each year of car and they were used in the dealer device departments by the mechanics.
The larger vendors sell them and the one for 1974 is about $45.
Good Luck!
Regards,
Alan
While the Haynes manual is o.k. in a pinch, there's a much better resource available for not too much money.
It's the GM Chassis Service Manual. There's one available for each year of car and they were used in the dealer device departments by the mechanics.
The larger vendors sell them and the one for 1974 is about $45.
Good Luck!
Regards,
Alan
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
I did too the tank off with premium and stabil for winter storage. But based on the marks on my garage floor which is level it happens every time I start it and hit the accelerator. Specifically today I went out, started it, looked under the car nothing, got in and revved the engine, looked again and there was gas on the floor. Thanks.
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
Hi A,
While the Haynes manual is o.k. in a pinch, there's a much better resource available for not too much money.
It's the GM Chassis Service Manual. There's one available for each year of car and they were used in the dealer device departments by the mechanics.
The larger vendors sell them and the one for 1974 is about $45.
Good Luck!
Regards,
Alan
While the Haynes manual is o.k. in a pinch, there's a much better resource available for not too much money.
It's the GM Chassis Service Manual. There's one available for each year of car and they were used in the dealer device departments by the mechanics.
The larger vendors sell them and the one for 1974 is about $45.
Good Luck!
Regards,
Alan
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
I got a binder from my insurance company so I could drive it to get an appraisal. It's currently only insured for the purchase price but several online appraisal tools are valuing it for quite but more and I wanted to make sure my bases are covered.
Burning Brakes
Joined: Aug 2004
Posts: 802
Likes: 1
I had a severe fuel leak from the carb when the carb float got saturated with fuel, then sank to the bottom of the bowl. Since the needle didn't shut off the flow, gas flowed over the top and down the engine side. This happened without warning. Luckily no fire since I smelled the gas and caught it in time. This was back in around 1980.
I learned how to dismantle the top of the carb, right on the engine, change and set the float, since this was my DD at the time.
Steve L
73 coupe since new
I learned how to dismantle the top of the carb, right on the engine, change and set the float, since this was my DD at the time.
Steve L
73 coupe since new
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
Finally had some time to go out and look at this again on my lunch. Took the air cleaner off, started it up, revved the engine, and ... nothing. I couldn't see any leakage. The plastic ring that the air cleaner sits on was cracked and the cleaner looked unlevel when I took it off. Couple of things I did notice. There was definitely residue on the passenger side of the intake manifold in the little wells in front and back of the carb. To me the residue looked like it was coming from the carb gasket on the back side but that is my untrained eye and it doesn't seem to me that the amount of fuel I saw on the floor could have come from there but I have no experience with carbureted V8 engines. The fuel lines are braided steel. I'm going to try to take a few good pics of this area and let you experts tell me what you think. Thanks in advance guys.
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
I had a severe fuel leak from the carb when the carb float got saturated with fuel, then sank to the bottom of the bowl. Since the needle didn't shut off the flow, gas flowed over the top and down the engine side. This happened without warning. Luckily no fire since I smelled the gas and caught it in time. This was back in around 1980.
I learned how to dismantle the top of the carb, right on the engine, change and set the float, since this was my DD at the time.
Steve L
73 coupe since new
I learned how to dismantle the top of the carb, right on the engine, change and set the float, since this was my DD at the time.
Steve L
73 coupe since new
Now that I'm thinking about it after what I looked at this seems like the most likely scenario. If the car had been sitting for 5 days today would that have allowed any saturated fuel to evaporate from the float? Whereas the other day when I checked it and looked under neath it had run more recently and there could have been fuel still in the float would would have made it overflow sooner? The crack in the ring supporting the air cleaner is directly above where I saw the residue on the back of the carb as well.
Burning Brakes
Joined: Aug 2004
Posts: 802
Likes: 1
Steve,
Now that I'm thinking about it after what I looked at this seems like the most likely scenario. If the car had been sitting for 5 days today would that have allowed any saturated fuel to evaporate from the float? Whereas the other day when I checked it and looked under neath it had run more recently and there could have been fuel still in the float would would have made it overflow sooner? The crack in the ring supporting the air cleaner is directly above where I saw the residue on the back of the carb as well.
Now that I'm thinking about it after what I looked at this seems like the most likely scenario. If the car had been sitting for 5 days today would that have allowed any saturated fuel to evaporate from the float? Whereas the other day when I checked it and looked under neath it had run more recently and there could have been fuel still in the float would would have made it overflow sooner? The crack in the ring supporting the air cleaner is directly above where I saw the residue on the back of the carb as well.
Steve L
73 coupe since new
Thread Starter
Instructor
Joined: Nov 2014
Posts: 101
Likes: 1
From: Quincy IL
Given the amount of fuel I saw on the floor this seems most likely. To my mind it seems logical it would need to run for awhile to flood the float and make it drop right? Or are there a number of causes for this?
