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Gas smell


wdoland

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I got gas!

Well a gas smell. After I ride around for awhile and park in the garage. I've looked under the car, checked the engine, fuel pump, fuel filter, and carb and don't see dripping or wet area. I don't smell it right away. I park, go in the house and 10 mins later the smell almost knocks you down. 

 

 

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Check your fuel line front to back. Also take a look at the fuel tank drain plug.

Doesn't take a big fuel leak to make a big smell in an enclosed storage building.

Maybe also as soon as you get back from a drive loosen the gas cap to check for any pressure/vacuum  buildup.

 

Some thoughts,

 

DJ

Edited by DJ194950
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Sounds to me like a classic case of percolation in the carburetor. When you park the hot car in an enclosed area the latent heat from the engine rises and causes the fuel in the carburetor bowl to vaporize. Same thing happens when I park my car in the garage and close the overhead door. Leave your garage door open for a few minutes and my guess is the smell will dissipate.

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Wdoland,

Don's right, the heat builds and the gas "boils" over in the Carb from the heat. Usually finding its way down to the Intake Manifold

through the throttle shaft bushing or connectors to the dash pot etc. then down to your manifold to evaporate quickly and stink things up.

This has been happening to me to some degree since 1973 when I bought my first 1948 Chrysler Royal but has gotten worse as gas octanes have risen.

I have always put the hood up and ran a large fan over the front fender to cool my car down after a summer/hot day drive.

As far back as I can remember there has always been a faint smell of gas after taking a ride, however, I think

the newer gas "octanes" and "addatives" make for a more volatile fuel, that newer engines with fuel injection require.

Remember back in the day fuel was like 77 or 78 Leaded Octane, not 87, 89, or 93 Un-Leaded Octane with ethanol additives.

That isn't to say you don't have another possible leak that requires careful inspection to find and repair.

Tom

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FWIW;

I have always felt that this was one of the more spooky aspects of having one of these cars and trucks.

As I started sorting out my truck a correction for this condition was high on my list. We all know that the manifold design retains a lot of heat after shut down.

My solution was to remove the mechanical fuel pump and install a vane type electric pump back at the tank. I have it wired to a separate switch. When I am ready to shut off my engine I have a procedure. First I shut the fuel pump off then I allow the engine to idle for about 30 to 60 seconds. This brings the fuel level down in the float bowl enough to eliminate the effects of percolation. As long as I remember to do this I get no gas smell or hard hot starts. Added benefits are no chance of fuel entering the crankcase if the original fuel pump diaphragm ruptures and it is a decent anti theft feature.

 

Jeff

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Sounds to me like a classic case of percolation in the carburetor. When you park the hot car in an enclosed area the latent heat from the engine rises and causes the fuel in the carburetor bowl to vaporize. Same thing happens when I park my car in the garage and close the overhead door. Leave your garage door open for a few minutes and my guess is the smell will dissipate.

 

Don nailed it. I think the new gas tends to percolate more than gas did back when these cars were built. Lowering the float level might help as well. All my cars show discoloration on the carbs and when I go in the garage after parking a car, it has that "hot engine" smell I never get with a new fuel injected car.

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In the above photo you can see two heat shields that will probably help to eliminate your percolation problem . Both shields are home made and both are held on with wire .  The aluminum cover on the float bowl is made from a soda can . They seem to be doing the job for me . For more information and larger pictures go to the truck side of the forum , page two and Hot Starting Issues . 

Edited by Jerry Roberts
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Kind of scary to think gas is dripping down on a hot intake and exhaust. Glad I invested in a fire extinguisher.  

Get a bigger fire extinguisher.

One thing I have noticed is that folks generally buy the small extinguishers.

Spend the bucks and get the bigger one especially for your kitchen. You usually only get one shot at putting out a fire and if you don't get it all extinguished with that first shot you are just gonna watch it burn. And check the charge on your extinguishers a couple times a year.

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The real danger here is walking away from the car and having this happen a few minutes later when you are not present to do anything about it, Size of fire extinguishers won't matter then. I felt like the best solution was one that effectively eliminated the potential for this to occur. With what I did I don't get any gas fumes at all......at any time. If you get used to smelling gas fumes whenever you use the car there is a chance you won't pay attention to them when you should.

 

Jeff

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Once in my youth I set fire to our second car, a '50 Chebby station wagon, which hadn't been running right.  I had the fuel line disconnected for some reason, and must have had a spark plug wire loose.  I cranked the engine only momentarily, starting a small fire which burnt itself out quickly.  My dad said that if the fire had done real damage, the insurance people would have been suspicious. 

 

If gas does hit a hot manifold, it will quickly evaporate (and smell).  A spark or flame would be need to ignite it.  Then additional fuel would be needed to keep the fire going.  

 

These cars have been like this from day one, and the rare fires have been due to something out of whack, or amateur tinkering.  Keep your fuel line tight and your plug wires connected. 

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  Doesn't have to be fancy. Under the carb in this order is, thin paper gasket, sheet metal heat shield, thin paper gasket, thick insulator, (I think from a slant 6), thin paper gasket.

  I had to go to a longer stud to mount all of this to the manifold.  It seems to have eliminated all the excessive heat to the carb, I think the insulator has the most to do with that, but the shield does keep direct heat off of the bowl.

post-68-0-01746100-1413824661_thumb.jpg

post-68-0-27329200-1413824888_thumb.jpg

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I had the same problem when I first got my car. On the advice of a member, I adjusted the float to lower the fuel level in the bowl about 1/32. Car runs fine & haven't had problem since. I know that the way I did it is not the CORRECT WAY but it worked. All I did was take the fuel line loose ( to see if the float was stuck, it wasn't). On my carb the tang on the bowl was right there, took fitting out & carefully tweaked tang. Put it back together & no more gas overflow.

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