A quick question about gasoline smell.

Aranimus

Member
First Name
Bill
Joined
May 27, 2019
Messages
21
Reaction score
20
Location
CA
Vehicle(s)
2018 Wrangler JL Sport S
Hi guys,

This may be an entirely stupid question (not being a mechanic and all), but I thought I would ask. From a cold start, when I move my JL from the driveway into the garage (or vice versa, backing it out into the driveway), I smell a fairly strong gasoline odor. It's sharp, and not what I would expect from errant exhaust fumes. I was wondering whether this was normal, and perhaps just a result of incomplete combustion from a cold start? I mean it's not a big deal, but I notice it quite often. No leaks, everything functions perfectly, so perhaps I'm just noticing something I hadn't before (in previous vehicles) since I finally cleaned my garage, and can finally fit a Jeep into it!

--Bill
Advertisement

 

GreyFox

Well-Known Member
First Name
Brandy
Joined
Oct 11, 2018
Messages
3,062
Reaction score
6,180
Location
Ohio
Vehicle(s)
17 JKU, 19 JL
Mine starts in a garage also and this is normal. Well, for me anyways. I have noticed it in other vehicles that I keep in the garage. I'm sure a more knowledgeable person will comment on the actual science behind it:like:
 

Placebo

Member
Joined
May 13, 2019
Messages
15
Reaction score
29
Location
Bay Area
Vehicle(s)
Something with 4 wheels
When you do a cold start, the engines run richer because cold gas is harder to vaporize and cold gas can condense. So what pretty much every single car does, is they run a super rich air fuel mixture to prevent any issues during a cold start. It's so rich that sometimes all of the fuel doesn't burn up and so you smell gas when you start your jeep in the morning.

Edit: I should add that this is normal behavior for cars on cold start. Now if you smell gas and its not a cold start, then maybe you should think about if you spilled any gas onto your jeep from the gas pump or if you have a leak somewhere.
 

The Fixer

Well-Known Member
First Name
Steve
Joined
Aug 7, 2019
Messages
454
Reaction score
431
Location
North Jersey
Vehicle(s)
2018 Mojito! JLS, 2018 Firecracker JLUSS
Build Thread
Link
Occupation
Teacher
Definitely normal for a "cold start" especially if ambient temps are below 50ish or so. My wife's JLUS and my former Charger R/T run rich on startup, especially in the winter months. I just got my own JL 2 weeks ago and it's been nice and warm so I can't comment on mine yet, but I imagine it will do the same thing.
 

Rahneld

Banned
Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,113
Reaction score
679
Location
Boston
Vehicle(s)
JL Wrangler
A somewhat sidetracked quick anecdote.

The engine light went on in my Wrangler. I brought it to the dealer who it seems properly diagnosed that I had not tightened the gas cap adequate: no less than 3 clicks.

I didn't smell fumes but the dealer's diagnostic equipment did detect them from the gasoline filling port until the cap was tightened. This leak was also detected by the rig's systems which then actuated the aforementioned engine light.

~~~~~~~~~~~~~
 
OP
OP
Aranimus

Aranimus

Member
First Name
Bill
Joined
May 27, 2019
Messages
21
Reaction score
20
Location
CA
Vehicle(s)
2018 Wrangler JL Sport S
Hey guys,

Thanks for the replies. From what Placebo and The Fixer said, I agree that it's just normal, and I guess I was just noticing it for the first time because I am now pulling it into the garage! Just goes to show, cleaning your garage will lead to confusion!

--Bill

PS. Rahneld, it seems odd that not tightening a gas cap would lead to some electronic diagnostic issue. After all, if an engine's performance depends on consistent air pressure or containment at the point of the gas cap, I would think all vehicles on the road would have problems!
 

telix

Active Member
First Name
Chris
Joined
Jul 12, 2019
Messages
35
Reaction score
13
Location
Los Gatos, CA
Vehicle(s)
2019 Granite Jeep Wrangler JLU Rubicon
I also have a very strong gas smell when starting from a cold start. It doesn't seem quite right
 

Notorious

Well-Known Member
First Name
Kevin
Joined
Feb 11, 2020
Messages
2,211
Reaction score
4,532
Location
North Texas
Vehicle(s)
2000 TJ Sahara
I also have a very strong gas smell when starting from a cold start. It doesn't seem quite right
Maybe lay off the refried beans at dinner? :CWL:

Try filling up at a different branded gas station and see if the gasoline still smells. Otherwise it is as the poster above mentioned.
 

Paluss

Well-Known Member
Joined
Feb 15, 2018
Messages
384
Reaction score
337
Location
maryland
Vehicle(s)
2018 Rubicon, 2013 Porsche 911, 2020 Harley CVO Streetglide
Interesting, not experiencing a gas smell at all and my JL is 2 years old. In the winter I remote start for a few minutes before I enter the garage and the garage door is closed, but I don't notice any gas smell. Now I do get a gas smell from my motorcycle which has an open air filter, but the JL air box is a closed system, may be worth a check by the dealer.
 

Maverick909

Well-Known Member
First Name
Brian
Joined
Jan 15, 2019
Messages
1,896
Reaction score
2,154
Location
SoCal
Vehicle(s)
2018 JLU Sporticon, 1976 GMC K15 Lifted on 35's
A somewhat sidetracked quick anecdote.

The engine light went on in my Wrangler. I brought it to the dealer who it seems properly diagnosed that I had not tightened the gas cap adequate: no less than 3 clicks.

I didn't smell fumes but the dealer's diagnostic equipment did detect them from the gasoline filling port until the cap was tightened. This leak was also detected by the rig's systems which then actuated the aforementioned engine light.

~~~~~~~~~~~~~
the fuel tank is pressure tested by the ECU. they do a leak test to make sure there is not anything wrong. when the fuel cap is not tightened correctly it will show a check engine light because of it. all new cars are setup for this
 

roaniecowpony

Well-Known Member
Joined
Dec 4, 2018
Messages
2,866
Reaction score
3,026
Location
90505
Vehicle(s)
2018 JLUR, 14 GMC 1500 CC All TERRAIN
Occupation
Retired Engineer
As Placebo stated last August, fuel does not vaporize well at lower temperatures. When the engine is cold, the fuel will attach to any surface it comes in contact with. Liquid fuel emits less and less flammable vapor as the temperature goes lower.

With a carbureted engine (I'm old) the fuel is atomized in the venturi discharge and then contacts surfaces from the throttle butterfly, intake manifold, ports, valves and cylinder head, cylinder walls, etc.. When it contacts a cold surface, it attaches and forms larger droplets and flows along the surface. Cold fuel does not emit as much vapor which mixes with air to form a combustible mixture. This makes it harder to ignite. These old carbureted engines had a "choke" that richened the mixture a lot in order to get a combustible mixture in the combustion chamber. It took a long time for the intake tract from the carburetor venturi to the combustion chamber to heat up, thereby allowing the engine to run with a leaner mixture.

When port fuel injection came along, the injectors were closer to the combustion chamber and there was less contact with the surfaces along the path to the combustion chamber. Also, many engines are designed with the injector very near the valve, which allows spraying fuel directly into the chamber. This helped in that less fuel was deposited on surfaces along the path to the chamber, which lowered the amount of fuel that got sucked into the chamber once the engine started. Since the injector is nearer to the combustion chamber, the surfaces downstream of the injector heat faster/sooner allowing fuel to vaporize. Better.

When direct injection came along, no fuel was deposited on surfaces along the path to the combustion chamber. All the fuel is metered into the chamber itself. Still there are cold surfaces in the chamber (head, cylinder, piston), but they heat rapidly once the engine started. So a direct injection engine still needs a rich mixture to start and run for long enough to heat those surfaces, but that is measured in seconds now instead of minutes. Better still.

Worth a read. https://www.businessinsider.com/her...-doing-to-your-engine-and-its-not-good-2016-1
If I lived in a cold climate, I'd use a full synthetic oil that had good cold lubricating qualities. If it was extreme cold, I'd use oil pan, block, transmission, differential heaters Then I'd stop worrying about a long slow warmup.
 
Last edited:
Advertisement

Diode Dynamics
 
Advertisement
Top