Gas odors

[DanEC]

I'm trying to track down why my car reeks of gas for about 2 days after driving it. I'm used to having good old exhaust fume odor in the garage after driving one of my old cars but the Cobra takes it to a new level and it is definately a gas stench instead of exhaust odor. I suspected fuel was perking off in my carb after it was hot but in removing the air cleaner after a drive, I don't see any gas flowing into the carb throats. Just in case I've just fit a couple 1/4 inch gaskets under the carbs and I will see if that makes any difference. I haven't had a chance to drive it since then. The tank in the ERA is vented so I assume the gas caps are non-vented, as is my Ceadress street cap. I carefully cracked open the gas cap after a recent drive and didn't sense any built up pressure so it seems to be venting OK.

I can't locate any seeps so far in all of the plumbing but I am wondering if one of my Holley 600 carbs is leaking some fuel into the intake. My Holley carbs are bare bones models and don't have externally adjustable float levels so it's not easy to check them. The base gasket on the front carb was covered with gas when I pulled it out to replace with the 1/4 inch one, but I may have tilted the carb enough in lifting it up to have sloshed some fuel out of the bowl through the idle slot or bleeds. This may just speed up my decision to get a custom set of BJ/BK restoration carbs.

Any other ideas that I might check out?

Thanks

Correction - The Ceandess gas cap is vented. Possibly I should seal off it's vent??

[tkb289]

Dan,

I had a similar problem with my (1) Holly 650 on my 302, the garage would smell like gas for a few days after parking the car.

Turned out to be the needle and seat in the float bowl was not sealing. There was a small sliver of what looked like glue or epoxy that deposited itself onto the tip of the rubber needle and allowing gas to drip into the carb and into the intake manifold.

Hard to say if you have the same issue, but it’s something to look at. Also, check your fuel pressure, are you running a mechanical pump or an electric fuel pump?

Good luck in finding the problem, keep us posted.

[HealeyRick]

I've also read that ethanol in fuel dissolves the rubber in braided fuel lines fairly quickly and will cause a gas smell in the garage. Might be something to investigate.

[SunDude]

Did you check whether the fuel is leaking/weeping from the tank/fuel sender?

I'm just about to replace the gasket in my car after noticing a strong gas smell in the garage and a small puddle on the floor.

[joyridin']

My car has the same. I thought it was the carb, but it smelled like the odor was coming from the back of the car. I put a plastic bag over the gas inlet, then closed the gas cap on the bag. Smell gone.

[DanEC]

I am kind of suspecting the front carb. I thought I would try it with the 1/4 inch spacer to eliminate fuel perculation before pulling the carb apart. Suspiciously, it seems that my oil level has increased slightly too - can't be sure as I may have just overfilled it slightly when I changed it.

I'm running a mechanical pump. I've felt all around all of the fuel line connections - I'm running all Ford reproduction fuel log, filter and lines. I haven't spotted anything underneath on the tank, fuel lines or hoses so far.
Fuel bowls on carbs are dry outside.

I don't think I should leave the vent on the fuel cap functional with a vented tank. I will try putting some tape over the vent hole before my next drive.

I think if the carb spacers and tape over the fuel cap vent don't do anything, then I will pull the front carb apart and see what I can find.

[lippy]

Dan, what I might try is to drive the car, let it cool a bit (maybe an hour), drain the carb (through one of the lower attachment bolts on each bowl), and pull the carb off to see if there is any fuel inside the intake.

My fuel was definitely percolating at first - I could see it through the sight glasses on the carb. I added a 1/4" phenolic spacer and insulated all the fuel lines under the hood. It solved the problem. Here is my post with the parts I used: Solution for fuel percolation/heat soak

Now, if I take the air cleaner off after a drive I can see some of the fuel vapor coming off the carb, and the level in the float bowls drops a bit over the next few hours and then stabilizes. But I don't smell any fuel.

[DanEC]

Lippy - good suggestion but it may be difficult to do on my car as I don't have sight glasses on my fuel bowls and with two carbs mounted backwards, my first-stage carb primary fuel bowl/screws are up against the rear carb. I can drain the rear primary and the front secondary w/o disturbing the carbs. Since the carbs are single inlet with a transfer tube, that might be enough to drain them to where they can't spill over. And then see if the stench lessens any.

I did decide to try the 1/4 inch spacers after reading your thread.

Thanks

[kevins2]

I checked my fuel levels by looking in the sight glasses with the engine running, as the manual instructs, and the fuel is right at the bottom of the openings as it should be. Only a small amount of fuel sloshed out due to vibration. If I ran the car on a hot day, parked it and then opened the sight glasses, what would be normal? Level down a bit after some cooling but still visible through the sight opening? If I was experiencing some percolating I should literally be able to see that happening immediately after turning off the engine, as Lippy described?

[patrickt]

I'm not joking when I recommend that you use a child to help you on this. Your "smell" sense is not nearly as strong as a kid, say, 13 or 14 years old. Let them smell a little gas outside so they know what it is, let it clear out of them a bit, drive the car and create the problem, and then ask them to sniff around to find the source of the smell. They will be able to find the source. I'm not kidding on this. Really.

[Mr Jody]

Originally Posted by DanEC

...Suspiciously, it seems that my oil level has increased slightly too - can't be sure as I may have just overfilled it slightly when I changed it.

I'm running a mechanical pump....

Dan – I experienced a similar gas smell on a passenger vehicle of mine, and it was the mechanical fuel pump. The diaphragm inside the pump can develop a hole, and the fuel can indeed get into the crankcase from there. Fuel will leak through this hole from the fuel side of the diaphragm with the fuel inlets and outlets, to the mechanical side with the cam operated actuator and thus into the crankcase (and of course these “sides” are actually the top and bottom of the pump, separated by the diaphragm in between).

On my particular pump, there was what I will call an ‘evidence hole’ manufactured in on the actuator side of the pump exterior. If there is a leak in the diaphragm, then fuel will be coming out of this hole when the engine is running. Best time to check this is when everything is cold and you first crank it so the fuel will not be immediately evaporating. In my case, it was easy to see, as fuel was squirting out of the evidence hole and not just leaking out. The smell went away with the fuel pump replacement.

I never saw an obvious rise in my oil level, so maybe most of my gas leak was exiting through the ‘evidence hole’, although I can’t help but think that some gas did get into the crankcase, so an oil change would be prudent. You may want to take a good whiff of your oil to see if you can detect a gas smell (although I would think that some evaporation occurs through the breather as the oil heats up). If you do a little googling on mechanical fuel pump leaks, you will probably see where one of the symptoms is a rising oil level.

[lippy]

Originally Posted by kevins2

If I was experiencing some percolating I should literally be able to see that happening immediately after turning off the engine, as Lippy described?

When I first had the percolation issue, I could literally see the fuel boiling through the sight glasses in the bowls.

[DanEC]

Originally Posted by Mr Jody

Dan – I experienced a similar gas smell on a passenger vehicle of mine, and it was the mechanical fuel pump. The diaphragm inside the pump can develop a hole, and the fuel can indeed get into the crankcase from there.

Mr. Jody - that sounds like a good hint. I will take a close look at it. When checking around for any sign of dampness on my fuel lines I did seem to detect a bit or oil or something on the bottom of my pump, so it bears a closer look.

Thanks

Originally Posted by lippy

When I first had the percolation issue, I could literally see the fuel boiling through the sight glasses in the bowls.

Yeah - these cheap Holleys (no external float adjustment) are really a headache. I need to get some decent ones. The last time I drove it I took the air cleaner off when I shut it off and listened and looked for any sign of perculation but couldn't detect any. Keith Craft was supposed to install a valley shield under the intake and I believe he did - which would help a little with the temperature at the intake, but maybe not enough.

Thanks

[DanEC]

Originally Posted by patrickt

I'm not joking when I recommend that you use a child to help you on this. Your "smell" sense is not nearly as strong as a kid, say, 13 or 14 years old. Let them smell a little gas outside so they know what it is, let it clear out of them a bit, drive the car and create the problem, and then ask them to sniff around to find the source of the smell. They will be able to find the source. I'm not kidding on this. Really.

Ehhh - I'm not too sure about this. I don't have any kids and if I go out and pull one off the street, haul him/her to the garage and tell them to sniff around the car and see if they can see where that gas stench is coming from - well, I'm not sure who I should fear the most, Mom and Dad, or the Police or both. Will you be defending me?

[patrickt]

Originally Posted by DanEC

Ehhh - I'm not too sure about this. I don't have any kids and if I go out and pull one off the street, haul him/her to the garage and tell them to sniff around the car and see if they can see where that gas stench is coming from - well, I'm not sure who I should fear the most, Mom and Dad, or the Police or both. Will you be defending me?

Well, that is a tricky one. I was hoping more for your own kids, or your grandkids. I don't think I would commandeer someone else's kids.

[lcrabtree]

On a warm restart after sitting for 15 minutes or so mine would be really rich and needed some serious revs to clear it out. Carb spacer solved it.

Lester

[289ERAkit]

My leak or smell was from the 90 degree fitting coming out of the tank. You may need to remove a plate in the trunk for access. It did not leak enough to notice any undercar anomalies as it was just enough to make that fitting damp and cause a gas smell. I refitted the brass 90 using Teflon Tape. So.... if this is it, then I would pull off the gas line to drain the tank..... toss that gas into your daily driver along with any old chain saw gas from last fall. Add 2-3 gallons of new hi-test to test with and let it set over overnight. If you try to use some type of goop that is suppose to harden at the fitting ...it will not work because the remaining gas in the tank will make a mess of it.... just ask me why I know that. Make sure the roll say's it's Teflon Tape right on it. BTY...any smell of gas is a bad thing and should be investigated. These cars take a big hit when they catch fire.

[DanEC]

Originally Posted by 289ERAkit

My leak or smell was from the 90 degree fitting coming out of the tank.

Other than clamping a piece of fuel line to it I don't remember much about that tank fitting. I'll check it out.

Thanks

[strictlypersonl]

The FIA's fitting is on the bottom of the tank, making the seal there absolutely critical. (There's no easy way to pull off the top of the tank.)
The 427 tank has the fitting on top, with a pickup tube to the bottom of the tank. Any leak there is mostly drawn back into the tank.

[DanEC]

Originally Posted by strictlypersonl

The FIA's fitting is on the bottom of the tank, making the seal there absolutely critical. (There's no easy way to pull off the top of the tank.)
The 427 tank has the fitting on top, with a pickup tube to the bottom of the tank. Any leak there is mostly drawn back into the tank.

I was trying to figure that out and suspecting the tank was probably different. Thanks for clearing that up Bob.