Mystery - Strong Fuel Smell

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doc540

doc540

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After a 40 mile round trip at highway speeds last Saturday I parked the Lancer in the garage.

Water temp on the highway was 160 and only about 165-170 when I pulled into the garage.

Everything was normal.

20 minutes later there was a STRONG smell of gas throughout my two car garage.

I jacked up the car and scanned the bottom. No puddles, no obvious drips, gas cap was secure.

No leaks anywhere under the hood. No gas stains around or below the carb or intake.

If I leaned close to the air cleaner I could smell gas, but not really strong.

YOU GUYS HAVE ANY IDEAS?
lancer engine4.jpg
 
1. Fuel filter should not be horizontal, it should be vertical or max 45°. See right-hand column of this.

2. Metal fuel line running right above head and hot exhaust manifold or header = this problem you're having. Do the Fuel line mod and fix this and the fuel filter orientation at the same time.

3. No heat shield under your carburetor. Put one.

4. 160° water temp on highway means your engine is not reaching operating temperature. Put the correct 180° thermostat back in it, see here.
 
I would lose that air cleaner for starters. Take a look and see if any of your rubber lines are wet or stained and check the seal at your fuel tank sending unit.
 
Sedanman said:
I would lose that air cleaner for starters. Take a look and see if any of your rubber lines are wet or stained and check the seal at your fuel tank sending unit.
Click to expand...

The air cleaner has something to do with the gas smell?

It's one of the few that clears the hood when using a Holley 390.

Checked all the lines and fuel tank sending unit. Just replaced the unit and gasket not long ago.

Fuel tank was between 1/4 and empty.
 
could be. They are the worst air cleaner to use and the foam can fall apart and drop down into the carb. I replaced my sender too but I noticed a gas smell in my garage too and noticed that it does have some seapage.
 
Sedanman said:
could be. They are the worst air cleaner to use and the foam can fall apart and drop down into the carb. I replaced my sender too but I noticed a gas smell in my garage too and noticed that it does have some seapage.
Click to expand...

Thanks
No way I'd neglect the foam long enough for it to fall apart though.
 
Heat will take stand off vapors right up thru that Bug-eye filter, which is foam that will harden & eventually crumble, & worse burns like mad if you get a backfire, find another
solution & ditch it ASAP, and put the heat shield Dan spoke of on.....................
 
Killer6 said:
Heat will take stand off vapors right up thru that Bug-eye filter, which is foam that will harden & eventually crumble, & worse burns like mad if you get a backfire, find another
solution & ditch it ASAP, and put the heat shield Dan spoke of on.....................
Click to expand...

thanks
Which heat shield is that? And does it lift the carb any higher?

What air cleaners do you know that will clear the hood? I'm having trouble finding a functional unit that clears.
 
Well, lets start with the base gasket You're using now, if it is the thin std. type, you will be adding another of the same plus the thickness of the shield at a minimum. They are
a "trim to fit" deal, You may or may not have to. The fuel line routing is again key because as the fuel in the carb evaps, the needle & seat will allow more in if it is trying to get
in, heat=vapor=expansion=pressure=more going in to the carb to evap while it's just sitting there.
 
Killer6 said:
Well, lets start with the base gasket You're using now, if it is the thin std. type, you will be adding another of the same plus the thickness of the shield at a minimum. They are
a "trim to fit" deal, You may or may not have to. The fuel line routing is again key because as the fuel in the carb evaps, the needle & seat will allow more in if it is trying to get
in, heat=vapor=expansion=pressure=more going in to the carb to evap while it's just sitting there.
Click to expand...

Thanks, understood.

Not doubting you, just confused.

Why would this suddenly become an issue on a cool day with low engine temp when it hasn't happened on 100 degree day runs with the engine temp at 200?

The ONLY "new" factor I can think of is I let the fuel tank empty down to 3 gallons or less. I usually top it off sooner.

Really puzzled here.
 
Your pic is a little shadowy, hard to tell how close the A/C lines are etc., what other air cleaners have You tried so far? Drop base jobs can run into kickdown linkages etc., but
how much clearance do You have above the choke tower on the holley?
 
@doc540 I fought this problem for years. Do all of the things @slantsixdan suggested and it should help.

I will add it wasn't until I added a good quality heat shield below the carb for the fuel smell to stop. Part of it is today's gas, and part of it is because the vast majority of carburetors do not have an external bowl vent, so the fuel just sits in the bowl and boils until it forces the vapors out wherever it can (into the air cleaner, down the throat of the carb, etc). I tried thick gaskets and it didn't make a difference, again, heat shield.

The heat shield I use is from - Home
 
doc540 said:
Thanks, understood.

Not doubting you, just confused.

Why would this suddenly become an issue on a cool day with low engine temp when it hasn't happened on 100 degree day runs with the engine temp at 200?

The ONLY "new" factor I can think of is I let the fuel tank empty down to 3 gallons or less. I usually top it off sooner.

Really puzzled here.
Click to expand...
Yeah, if the temp is that cool outside, and You haven't changed anything else it wouldn't follow to be only heat related............ was the garage warmer than outdoors
by any real amount? If the tank were mostly vapor and you pulled it in to a warmer location, a lot might get pushed out the vent line from the tank. you wouldn't be
able to see that, but the odor would be by the rear wheel more so than the engine.
 
Killer6 said:
Yeah, if the temp is that cool outside, and You haven't changed anything else it wouldn't follow to be only heat related............ was the garage warmer than outdoors
by any real amount? If the tank were mostly vapor and you pulled it in to a warmer location, a lot might get pushed out the vent line from the tank. you wouldn't be
able to see that, but the odor would be by the rear wheel more so than the engine.
Click to expand...

Sherlock, you may be on to something.

The girls might have been doing laundry and running the dryer which is vented into the garage. Outside temps had dropped into the low to mid 50's and were headed to the 40's.

I'll try it again under similar conditions with a full tank, sniff the vent line and report back.
 
I was just relating to a fellow tech about an extreme case of this. Decades ago our private shop serviced the vehicles for a sports equip reconditioning company, one of the
E350 fleet was dropped off overnite for service the next day. We pulled it in for the nite as it was single digits outside, who wants to work on a 5deg vehicle right? Unfortunately
the hired help filled the tank on the way over, at a station that just got a fresh load of fuel, oh and he topped her off good,lol! The shop heater was a hung gas unit that was
pointed right at the van,.... the next morning there was a puddle almost the size of the van under it, & the entire building was so heavy w/fumes.........I still can't believe that
place didn't blow up!! The fuel swelled up and forced its way out the canister vent all over..............
 
I would suspect the fuel tank vapours expanding in the warm garage and exiting the tank, as suggested. If it hasnt been said yet, one more safety related item. Get rid of the plastic fuel filter. Plastic and glass filters can crack or rupture......you get the picture. Steel canister filters only! And yes, the chrome mesh / foam air cleaner is a underhood fire waiting to happen if you have a backfire through the carb. I have been there.
 
I was wondering about the carb. Are you running rich? It looks bigger than a stock carb. About 8 years ago I put a 750 carb on my modified 340. Every time I drove it I smelled like gas, the car smelled like gas, and the garage smelled like gas, but there were no leaks. I jetted the primaries down 2 notches, and that problem went away.
 
Sedanman said:
I would lose that air cleaner for starters. Take a look and see if any of your rubber lines are wet or stained and check the seal at your fuel tank sending unit.
Click to expand...
if that air cleaner has the foam element - lose it! u can get a paper filter to fit that thing, I did on one of my past hotrods.
 
I had a fuel tank leaking one time-Started out of no where. It was a little pin hole in the tank. I'm sure you already did it, but don't forget to check the gasket where the filler tube goes into the tank. And the where the fuel line goes in.
 
doc540 said:
y'all happy now? View attachment 1715013527
Click to expand...

Well, it's not us that have to be happy, it's you. Looking at this pic, I see the fuel filter still in the wrong place, and it's upside-down (this is worse, not better), fuel line is still metal and still runs close to hot head and header...doesn't look like you read post № 2 in this thread at all.

(Also, do yourself several enormous favours including making a big improvement in the fuel odour problem: wrap those headers clear all the way from the head down to the collector flange, then start wrappin' again for at least a few feet of the pipe behind the flange.)
 
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slantsixdan said:
Well, it's not us that have to be happy, it's you. Looking at this pic, I see the fuel filter still in the wrong place, and it's upside-down (this is worse, not better), fuel line is still metal and still runs close to hot head and header...doesn't look like you read post № 2 in this thread at all.

(Also, do yourself several enormous favours including making a big improvement in the fuel odour problem: wrap those headers clear all the way from the head down to the collector flange, then start wrappin' again for at least a few feet of the pipe behind the flange.)
Click to expand...

Thanks, you've always been very helpful.

Would you please post a picture of how a proper fuel line is constructed and run on a SS?
I'm not sure what kind of fuel line to use (all rubber?), how to get it from one side of the engine to the carb without it crossing the head and intake/exhaust, and where and how the fuel filter should be positioned.

And what do you recommend I wrap the headers with? There are multiple materials out there.
 
I believe Dan posted links to the line routing etc. in His post above, so check them out if You haven't had a chance yet. I know it isn't always attractive, but heat sleeve is not
a bad idea on the lines in the vicinity of heat such as what You've got there , if rerouting isn't desired/an option. And always use the least amount of rubber line, even if it is
SAEJ30R9 EFI hose, teflon inner lined or not, it should only be used where it has to be. Definitely NOT over sources of high radiant heat!
 
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