High outside temperature causes faint fuel odor, and reluctance to start.

tixer

tixer

Lincoln Evangelist
Staff member
Paid Member
Sorry about the odd title, but this is (to me) a strange set of symptoms.

I've noticed only recently, that when driving the car when the outside temperature is high, (90+ Fahrenheit) I occasionally detect a very faint fuel smell from under the hood. It may be nearer the passenger side, because the vent will sometimes pull the odor inside the car. The smell is faint enough that I cannot pinpoint the source while sniffing around under the hood.

The other factor is that since I first noticed this problem, the car is somewhat hesitant to start. 8-10 cranks before it fires, instead of the usual 3-4. (this has been happening consistently, even on the days I do not smell fuel)

I'm wondering if there may be a failing vent or valve in a fuel line, that could be leaking slightly, and causing the fuel to run back into the tank when the car sits?

Once running, the car seems to run and drive fine. no discernible stutters or misses are present. IAC, TPS, and PCV are all new this year, but were replaced well before this problem presented itself.

If anyone has any thoughts, random ideas, or experience, I'd appreciate it.
Thanks!
Mike
 
Does it happen when the car is more towards full of fuel rather than towards empty? I was thinking expansion of fuel in tank and overpowering the charcoal canister.
 
We had this driving home from Carlisle one year, I could smell it from the passenger side, more than Mike on drivers side, and vice versa. We searched for anything, and found nothing. Sleeper was right behind us so he stopped and explained it could have been from the lowering fuel or something like that? Didn't have any problems, it was just very hot and a very long drive, although this had to have happened after only 4-5 hours into the trip since Dave hadn't split off for Detroit.
 
I would suspect the EVAP system. I know on the Gen1, the charcoal canister is mounted with the suspension compressor. It is not uncommon for the vacuum line to have a leak or the purge valve or vent valve malfunction. Realize the purpose of the EVAP system is to purge fuel vapors from the fuel tank into the intake when driving.

http://www.youtube.com/watch?v=IzfR84T6pBY
 
I helped do some evap system testing in Arizona once.

I learned that the boiling point of gasoline starts at 100 degrees.:eek:

I agree, check the evap system, the purge valve, and hoses.:)

Most of the Gen 2 system is in the metal tray under the trunk
 
I had this problem in my '95 Taurus SHO. It turned out to be the vent valve that is inline to the hose that ran from the intake to the carbon canister. It wasn't venting the fuel vapors into the canister like it should so they were building up.

I changed the vent solenoid and all the vacuum tubes since they were old and brittle. Problem was solved.

If I remember correct the valve and the canister (at least in a Gen I) are inside the passenger side fender (near the air compressor).

Although they are very different vehicles I'm sure the systems operate rather similarly, and I could have swore I saw the same vent vale in there by the air compressor when I swapped it.

Doug
 
You can also test the fuel pressure loss theory by priming the fuel pump before you start the car.
 
You live in the rust belt, this is on your 97 I assume.
Pull down your e-vap tray.
Check the canister purge solenoid.

I believe it vents vapors when things get up to temp.

First thing I would look at.
 
Last edited:
Thanks for the replies, guys. (and gal :) ) We're definitely onto something here. I just realized another symptom. When stopping for fuel lately, opening the gas cap has been releasing quite a bit of pressure that I never noticed previously. (regardless of the warning about said pressure on the cap.)

With the system not venting properly, it is easy to see how the pressure would increase, and force vapors out in places they should not be. I'll order up a new solenoid, and when the weather cools down a bit, I'll dig in. (the forecast says 97 degrees today)

Man I love this forum.
 
Gas is formulated for the seasonal temperatures, maybe they don't know how to formulate it for the hot weather by you, or you got spring time gas. :)
 
naah.. it's been doing that last thing since at least last year. and even did it in California. :D

The car doesn't get driven in winter, so formulation should be fairly consistent. I do sometimes regret getting it tuned for 92 octane though. it's tough to find. I generally end up with 91 instead. Hopefully the car doesn't mind.
 
tixer said:
naah.. it's been doing that last thing since at least last year. and even did it in California. :D

The car doesn't get driven in winter, so formulation should be fairly consistent. I do sometimes regret getting it tuned for 92 octane though. it's tough to find. I generally end up with 91 instead. Hopefully the car doesn't mind.
Click to expand...

At what elevation was the car tuned and at what elevation do you live?
 
This was Lonnie's mail-order tune with the SCT X3. Even if he didn't specifically tune for my elevation, Wikipedia lists the elevation of the city he's based in as 951 feet above sea level, and my own home is at 1,000 feet above sea level. Close enough, I'd guess. :D
 
tixer said:
This was Lonnie's mail-order tune with the SCT X3. Even if he didn't specifically tune for my elevation, Wikipedia lists the elevation of the city he's based in as 951 feet above sea level, and my own home is at 1,000 feet above sea level. Close enough, I'd guess. :D
Click to expand...

The higher you go the less dense the air and the less octane you need.
 
I noticed the smell of gas in my 97 the other day when it was 95 degrees out. No starting or other problems though. I opened the gas cap, there was no pressure built up.

Stupid Gen 2 inadequate evap system.:D

The 97 smells and the 98 won't let me fill the gas tank all the way.:)
 
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