Fuel Smell - Can't find source

[johnnyzoom]

Since I've had this Comet there's been an intermittent fuel smell and I can't find the source.

Thought it was fuel pump, that's been resolved. Carb apparently in good shape, no leaks that I can see, float and needle seat functioning correctly, took choke off two weeks ago during rebuild, and it runs better than ever. Windows up, no smell. Any window down it's there, but stronger with driver side window down than passenger. Gas tank is about six years old, can't find a drop out of place. Never could find a leak in the fuel line, but I went ahead and replaced that today, no change. Spark plugs are grey, just about right, no signs of fouling. No colored smoke in exhaust. Oil doesn't smell like gas.

Accelerator pump shows no signs of leakage, can observe shot of fuel when pulling throttle. But smell IS most noticeable when accelerating, don't know how else to check that.

I can't find any evidence of a leak anywhere. I'd swear it's fuel, it's got that sickening sweet quality that hangs (not the coolant sweet), I really don't think it's exhaust but I've definitely been wrong before.

Anybody see what I'm missing or have any ideas? Something going on with the cylinders? It's not your normal "old car" thing, it'll give you a headache after a short while, and perhaps most tragically, the better half doesn't want to ride in it, and I can't blame her!

Thanks guys- Johnny

64 Comet 404 200cid automatic

 

[rbohm]

8) try running your engine at idle and tracking the fuel line fittings. also check any soft lines carefully. i had a fuel leak in my grand marquis that could only be spotted when the engine was running. just turing the electric fuel pump on had no effect(go figure).

 

[lightnin-boy]

I get a stong fuel smell when my tank drops below 1/4 full, stronger when the vent window or side window is open. I'm not sure why this is, I've chalked it up to a poor trunk seal and the fumes being drawn in from the trunk, but again if the tank if it is full then smell is substantially reduced. oh, 1965 Mustang coupe.

Kirk

 

[Anonymous]

the filler tube that is made of rubber is notorius for leaks on mustangs.,....is it the same for all old fords?

Its vapors...not necc a leak per say...but check that out

 

[Anonymous]

Could it be that the float setting is a bit high and you have fuel in the manifold continually?
Just a thought.
Doug

 

[Anonymous]

Here in Ga. we have this pesky little wasp called a "mud-dauber", they are notorious for crawling into small holes and packing them with a mixture of mud/eggs/and spiders. The mud is a hatching environment for the egg and the spider is food for the wasp larvae when it hatches. They love the gas tank vent tubes of early Falcon/Comet's. Then as you drive vapors build up and cause all kinds of little hard to trace problems such as hard to fill gas tanks and leaky seals around filler necks and fill tubes. They will completely incapacitate weed eaters by packing the exhaust port in the little muffler. My 62 drove me crazy with little issues till one day i crawled under it with an 8" piece of electric fence wire and poked the vent tube then blew it out with air. Now it doesn't puke gas when i fill it and the nasty smell of gas is gone cause now it vents going down the road instead of escapeing slowly while parked. These old cars vented to the atmosphere instead of the closed system on newer vehicles. If plugged the vent line will cause excessive pressure on the entire fuel system resulting in little leaks that are near impossible to find and even more impossible to stop. Goind down the road the fuel sloshes and builds vapor also simple evaporative expansion adds to the mix. Also it is more of an issue the when the tank is not full as more evaporation occurs when the is more surface area and more sloshing not to mention the fact that you can't compress a liquid so the more gas in the tank the less pressure that can build up.

 

[Anonymous]

I took apart my old Wonderbar radio out of my 61 Vette and found a Mud dauber had built a nest inside. My neighbor had problems getting an old Camaro to run after he restored it. Turns out some June bugs had crawled into some hoses and tubes when they were laying around the shop un-capped for months.
Doug

 

[addo]

I've had them in my vent tube, too. (I mean the car's.)

 

[simon]

as if there was any doubt of that, Addo...!

 

[johnnyzoom]

Thanks for all the suggestions.

I was not specific enough, it does seem more like vapor. My carb came with the vent valve blocked off, I've tried running with and without it plugged, no difference in performance or smell.

Read all the posts about gas tank venting and drilled two small holes in the cap (hard time finding a regular vented gas cap around here), unfortunately no difference.

Honestly can't find a vent hose on this gas tank! Previous owner replaced tank, might have skipped it. I'll look harder and definitely check for any insect life.

If there isn't a vent hose I guess I have to fabricate one, or is there an alternate solution?

Thanks again everybody-

Johnny