charcoal canister

[mikes456]

I have a 1973 Cuda that had a charcoal canister. The canister has been removed and the line was capped along the frame rail in the engine compartment. I believe that this has caused the following problems.
1.) When the fuel tank gets below ½ to ¼ tank I start to have a fuel problem which is more prevalent in hotter weather. What I am experiencing is that my clear glass fuel filter is no longer filled solid with gas. The car has an electronic fuel pump mounted by the gas tank. I do not have a fuel regulator and do not know if the pump has an integral one.

2.) No matter what the outside temp. is or the fuel level of tank shortly after the car is shut down the fuel in the glass fuel filter stars to bubble. I’m not sure if it’s boiling or just draining out of the fuel filter in to the fuel line below (tank side).

3.) After long ride on a hot day the car smells of fuel but there are no leaks.


I have done the following to solve this problem with no success.
1. I removed the vacuum cap blocking the canister line and attached about 6’ of 3/8” line coiled it up and placed a fuel filter on the end of it. This coil style vent is higher than the gas tank.

2. I switched the non vented gas cap to a vented, neither cap changed the problem but I think things are a little better with the vented cap.

3. Installed a mechanical fuel pump still same problem. (the electric one is in use now)

For the record the motor does not run hot. It has a large cam 484 lift, ported/ polished heads w/202 valves, headers, torker intake, a Holley 750 cfm double pumper duel feed with mechanical secondary’s carburetor.
All the hoses between the fuel evaporator and gas tank have been replaced.
Does anyone have the diagram for the canister? More importantly how can I bypass it and make an adequate and safe vent?
Mr. Gasket makes a universal canister but I rather just not have one. The space were the factory canister was has a Cam Dynamics vacuum booster so my power brakes work better I need this due to the camshaft profile.
I have had this car for 20 plus years and my work around have been to keep a full tank of gas in it
tried to attach photos of coil vent and fuel line route but could not?

Any ideas? thanks mike

 

[moparleo]

You say that you have had the car for 20 years. How long have you had this problem? Did you change something recently that may have started this problem? Have you checked the fuel tank sending unit ? It may be corroded in the tank. If you use an electric fuel pump, you should always us a fuel pressure regulator. Normal pressure should be 6 to 8 psi at the carb.
Diagnosis is always a methodical step by step process. Remember that most problems that you run accross are going to be simple ,stupid, stuff. Always check the simplest, obvious stuff first. Humans tend to make things more complicated than they really are.
Keep us posted on your progress.

 

[challenger6pak]

It does sound like a partial blockage. The sending unit also has a filter on it that could be dirty. You say the car smells of fuel. In between the rear shocks is a fuel evaporation tank with several lines coming off of it. Have you checked it? They are known to rust on the top where they meet the car floor.

 

[mikes456]

My guess this problem started 18 years ago after I removed the canister.
Nothing has been changed other then the following which was done in the last year.

1. I removed the vacuum cap blocking the canister line and attached about 6’ of 3/8” line coiled it up and placed a fuel filter on the end of it. This coil style vent is higher than the gas tank.

2. I switched the non vented gas cap to a vented, neither cap changed the problem but I think things are a little better with the vented cap.

How do I check the fuel tank sending unit, pull the tank?

I will be installing a fuel pressure shortly.

 

[mikes456]

If the evaporation tank has a hole in what problem would that cause the smell or the fuel pressure issue?
I only get the smell after a good ride, stonger smell in the summer. The car is in a garage and the garage never smells when the car is sitting. The factory rubber lines to the evaporation tank were replace about 15 years ago because the were rotted. I though this would fix the problem but it did not. I have been taking the easy way out by keeping a full tank of gas in the beast. I have more spare time now that my child is older and i'm starting to tinker and fix the things that need to be done.

 

[72RoadRunnerGTX]

Can’t tell from your posts, are you actually experiencing fuel starvation symptoms with low fuel tank levels or just the appearance of bubbles in the fuel filter? I would verify fuel pressure at the carb with a pressure gauge under the conditions in question. Most aftermarket fuel pumps intended for carbureted street use are internally regulated around 6-7 psi and do not require an external fuel pressure regulator. As mentioned, the filter screen on the tank pick-up should be checked/cleaned or replaced. Requires removing the sending unit from the tank, should be able to do that without removing the tank from the car. The Evaporation Control System, as originally designed, also acts as the fuel tank vent system, the line running to the charcoal canister is the tank vent, plugging it off, on an otherwise intact fuel system, could very well lead to fuel starvation. Sounds like you have opened it up and provided additional venting at the cap without a resolution, pointing back to a pre-pump restriction of some kind. If the pick-up sock screen has never been serviced in 40 years, it’s way past due anyway.

With the fuel smell issue I would recommend dropping the tank, tank vapor separator, and vent hoses for close inspection, sending unit service is much easier tank removed. I’d be looking for failed solder connections around the hose nipples, rust through holes in the vapor separator, filler neck grommet, and further hose deterioration. Warm fuel in a warm tank on a hot day generates internal pressure in the tank and vapor separator system components. Leaks in this system will generate smells that will be more noticeable under these conditions rather when cool and parked for any length of time.

 

[challenger6pak]

It could cause both or either. Since it only smells when you run it, it is a good chance it is seeping somewhere. I would start at the rear of the car and follow the lines, just like the fuel does. Check everything out from one end to the other. You will find it. Like Leo said, it is a process.

 

[moper]

Fuel smells are very common with the modern 10% ethanol fuels and open element air cleaners. Where is the fuel smell? at the back? Under the hood? in the passenger compartment? When was the last time the carb was rebuilt?
You car will have an evaporative manifold above and in front of the tank. It has 3-4 hoses on it and they are commonly rotted and kinked closed and never serviced. I've also seen the cannister tube blocked and with the non-vented cap it will create a no fuel situation after driving. So snoop around. The easiest way to allieve the issues is to take the hose from the sender (small vacuum line) that goes to the evap manifold and just put a filter on it, moutned up above the rear axle higher than the tank. Then you can eliminate the rest of the system and runa vented cap. I think the smell is the carb - not the tank.

 

[mikes456]

Fuel smells are very common with the modern 10% ethanol fuels and open element air cleaners. Where is the fuel smell? at the back? Under the hood? in the passenger compartment? When was the last time the carb was rebuilt?
You car will have an evaporative manifold above and in front of the tank. It has 3-4 hoses on it and they are commonly rotted and kinked closed and never serviced. I've also seen the cannister tube blocked and with the non-vented cap it will create a no fuel situation after driving. So snoop around. The easiest way to allieve the issues is to take the hose from the sender (small vacuum line) that goes to the evap manifold and just put a filter on it, moutned up above the rear axle higher than the tank. Then you can eliminate the rest of the system and runa vented cap. I think the smell is the carb - not the tank.

The carb is new from last August and I had the same issue with the old one.
The old carb had been rebuilt at least four times over the last 20 years and it was getting worn.
The hoses at the fuel evaporator where replaced a while ago but are still in good shape.
Changing the hoses did not change anything but they were due so I did it.
I will try your method of bypass but I have one question. By putting a puting a filter on the end
of the vacuum line it does this become a safe vent? I don't want a spark from a cigeratte tossed
from a car onto the road ingniting my gas tank. I my previous post I stated have a similar vent in
the engine compartment at the line that ran from the canister to the evaporator. Are we talking
about venting the same line but you are saying to do at the tank rather than the engine compartment?
The fuel smell is not coming out of the coil style vent, or by the gas cap so you might be right it could be
the carb.

Thank you for taking the time to write.

Mike

 

[moper]

The factory vent for the '70 cars was a long tube that was designed to seperate out the liquid fuel from the vapors. It ended within the frame rail and that's where teh gasses exited the system. The only issue I've ever had with the filter is if you have a full tank and are driving a road course - occasionally liquid fuel will make it out of the filter. A check valve would end that but honestly I only had one customer that drove that hard...lol. There is virutally no risk of fire. I won;t say there is none - I'm sure there is some chance, but in terms of odds I'd put it at half as likely as getting killed by road debris flying throught the windshield. Not quite a "struck by lightening", but not very good.
You might also want to drive the car and get it warmed up, then park it ad riase the hood. If you sniff around you should be able to tell where the smell is the worst. You might also want to check the firewall and floorpans for missing body plugs or open holes/seams and check the cowl seal. Vapors from the engine bay should not be entering the pass compartment unless the heater draws them in from the surrounding air.

 

[mikes456]

any chance of getting a photo of your vent system?