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Fuel Smell Diagnosis

Nick S

Well-known member
Joined
Dec 10, 2004
Messages
85
Location
Herndon, VA
Ok, this might be a little long, but this "problem" is driving me crazy. About a month ago, I filled the car up with gas and drove home. The next morning when I was driving to work with the driver window down and vent on, I started smelling gas whenever I stopped at a light. The scent was kind of like what you get when you are at the gas station. Not super heavy, but you will get a whiff of it every now and then enough to notice the gas smell. Well, I assumed that it must be someone else's car because mine does not leak gas. Unfortunately, it seems to be coming from my car. Over time, I have noticed that the smell tends to occur more in the morning than when I drive home from work in the evening. Not to say that it isn't there from time to time in the evening, but it is always there in the morning.

Anyway, so I start doing research on here and in my shop manuals for the car and armed with that knowledge I take it to the Chevy dealer. I told them to replace the fuel filter (was time to have it done anyway) and to try and hunt down the smell. They told me that they don't smell anything and that everything appears normal. I wasn't really satisfied with their explanation of their diagnosis (longer story). So, still smelling the fuel, I took it to another Chevy dealer. This dealer tested the fuel pressure, took it on a test drive, let it sit over night and started it in the morning, looked for leaks, etc. and still nothing. (By the way, they charged me nothing for this. I thought that was nice of them.) They said that the car was holding fuel pressure and that if there was a problem with a leak or with something in the EVAP control system that they would like to wait for a code to be thrown before they start randomly throwing parts at the problem.

Well, I started the car this morning and immediately smelled gas. I don't know how people can miss this smell. It smells like it is coming from the back of the engine, but you never really know with a gas smell. The smell could be coming from anywhere, but it is definitely not coming from the rear of the car. I read about people having hard start issues which indicated a leaking fuel injector, and have noticed that the car turns over quite a few times before it will start every once in a while in the morning. But I wonder if I am thinking about this too much now. I thought that it might be the ethanol that is in the gas now (10%) and I added some gas dry in case there is any water in the gas. That did nothing.

The car has been running fine except for a slight rough idle that I have been chasing for a few months. I replaced all of the plugs and wires and cleaned the throttle body before this smell problem, and that did not seem to change the idle. I never thought the idle was a problem until someone mentioned to me that it seemed to stumble a bit while idling.

Another thing, the car is not running too rich or too lean when I watch the long and short term fuel readings.

I have a hard time believing that this is normal and that I should just let it go. However, after two dealers have told me that they don't smell it and don't see a problem, I'm wondering if I should just live with it and my burning eyes (from the smell).

Sorry that this is so long and wandering of a post. Anyone have any suggestions?

Thank you.

Nick
 
Could it be the charcoal canister?
 
Yeah, I was thinking canister too. However, according to the GM manual for the car, if the canister were to go bad there are a number of codes that pertain to the EVAP control system that would most likely set (I think 4, I don't recall them off the top of my head.).

I was reading the manual the other night and it mentioned that it is possible if one or two of the parts of the EVAP control system are bad that they might release gas fumes from the canister back toward the intake at a time that the computer did not determine. Now, this would account for the smell. However, if this happens, it is supposed to throw a code. I have no codes.

I still think that this is funny. The guy at the first Chevy dealer told me two things. One, he said to put a piece of cardboard under the car and look for leaks. I thought that gas evaporates in air. Maybe I would see the stain left behind. Who knows. Two, check my spark plugs. Well, checking your spark plugs is a way of finding a leaking fuel injector. However, there are other ways of finding the leaking injector before you get to that step.

I was thinking of just replacing the parts of the EVAP control system one by one. Of course, that could get expensive. Oh well, just thinking out loud now.

Nick
 
I bought a fuel pressure gauge last weekend. After two dealers checked the pressure and said that it was ok, I will still probably have to check myself just to make sure.
 
A few thoughts on this one. If your car has to be cranked for a bit to start when cold, or after sitting for an hour or so, and you are smelling gas, I would check the vacuum line coming from the fuel pressure regulator to the intake manifold. If you have any fuel in that line, even a drop, you have a ruptured diaphragm. And it may be small enough that a leak down ck of the fuel pressure will be within limits. I found this to be the source of my extended cranking problem. R & R the regulator, and the engine springs to life with a touch of the key. Also, look under the car near the fuel lines after the car has been sitting for a bit after shutdown. My fuel filter had a small leak, I began smelling fuel near the passenger side of the car. Tightened the line and all is well again. Good luck.
 
I had fuel odor problems with my 78, so I don't know how relevant this will be with your C4...

My first problem was an overwhelming fuel smell in the car. Enough to make me lightheaded and have to pull over several times trying to get to the mechanic.
They checked everywhere under the hood and everything was just fine. They couldn't find anything, adjusted the carb all over the place, and sent me home. I still had the overwhelming fuel smell so I drove it to my friend's son's auto wrecking yard. He found the problem.

My fuel lines over my gas tank were old and cracked. They leaked over the top of my gas tank, dripped down and filled my tire carrier AND dripped over my HOT MUFFLERS!
Replaced the fuel line and things were grand.

Until a few years ago. We rebuilt the engine and in the summer I would notice on hot days if my gas tank was less than 1/2 full I would get whiffs of fuel smell in the car with the window down/cracked. I just kept the tanks above 1/2.
Recently we replaced my original (professionally rebuilt) carb for a brand new one...and now I have no problems with fuel smell. Replacing the carb has also cleared up a few other driveability issues I was having, but I'm not sure what my carb/fuel-smell solution could do for your fuel injected C4... keep looking, and I hope it is a simple and quick fix.
Heidi
 
Fuel Pressure Regulator Leaking

First, thank you to everyone for the different suggestions and examples from your own experiences. This problem has been baffling; however, I think that I found the problem tonight. I left work tonight and walked out to the parking garage to get in the car and drive home. Well, before I started the engine, I decided to look at all of the lines and hoses around the intake again. I cleaned up some stuff and everything seemed to look ok, but I could still smell gas. The smell of gas has always seemed to be strongest near the back of the engine near the fuel pressure regulator. The rubber o-ring that is connected to the regulator has looked damp in the past and the regulator itself has seemed a little discolored. I have wondered if something had leaked on it in the past or if it was leaking, but I could never "see" a leak.

Well, after cleaning everything up, I started the car. I went back to look at the regulator and now it looked wet. The lighting wasn't perfect. So, I thought that I might be seeing things. As I went back into the car to get a rag, I caught a glimpse of something dripping off the fuel pressure regulator onto the intake. I did a double take and just stared as I watched a constant dripping of gas from the fuel pressure regulator. Wow!! I found it. A bad fuel pressure regulator (or at least a bad o-ring, I'll find out definitively tomorrow).

Of course, this raises a couple of questions in my mind. One, how could anyone not smell gas with a leak like that? Two, how could a mechanic searching for this problem miss it? This really makes me wonder about the quality of work that is done by the majority of "dealers". I went to two different Chevy service departments and told them that I smelled gas and asked them to find/fix the problem. Both of them sent me away after "looking" at the car and assured me that there was not a problem. I wonder what they would have said if the car had caught on fire and burned up, after having been through their service department and assured that there was no problem. "Oops, we're sorry. I guess we missed that one." Although I think I have resolved my problem because I kept reading, asking for input from people here, and investigating the problem on my own; I wonder what happens to people that don't have the time or the mechanical knowledge to pursue their car problems further. For most people, the word of a "professional" mechanic is gospel. Unfortunately, a gospel that in certain circumstances can get them killed. It is kind of disappointing when you can't always count on the word of a "professional" of any type anymore.

Nick
 
Wow! I'm very happy that you were able to find the problem and it appears it will be an easy fix. Yea! I had the same frustrations as you with my huge fule odor problem...they couldn't find it, but when I took it to another person (<5min later) I told him the symptoms, he bent down under the back of my car and showed me the dripping/running fuel marks on my mufflers.
I went back to the garage and showed them. "There. It's right there!"

Sometimes, you just need to find the right person who has encountered the problem before...or be like you...in the right place, at the right time and looking for something, but able to recognize it when you see it. Serendipity.

Sometimes I think mechanics treat us the way Doctors tend to treat our 'complaints'... "Oh, it's nothing, I'm sure it's just in their head...lets do something totally useless, it lets the customer/patient feel good to think we did something and send them on their way."
Heidi
 
Ah,the ole leaking fuel pressure regulator again. Ya know I bought a fuel pressure guage so I could diagnose my cold start extended cranking problem. I followed known troubleshooting procedures, pinching the rubber fuel lines back at the tank one at a time, that guage would hold pressure for about 5-6 minutes then gradually start losing pressure. I stopped recording results after 20 min on the leak down ck and it still had approx 20 psi. I discounted the fuel pump and regulator as being bad. But, I wouldnt let it go. No way should you have to crank an electronic ignition/fuel injected engine for more than a few seconds to start it. I kept checking and inadvertantly found the ruptured diaphragm on the regulator as I was removing the vacuum line out of the way to again hook up the test guage on the fuel rail port. Not making excuses for the mechanics as they deal with this stuff day in and day out, but I consider myself a good wrench, but sometimes you just get lucky in finding the source. Good find, by the way the regulator is an easy R&R you'll need 3/8" and a 5/16" fuel line quick disconnect tools to remove the lines.
 
Yep, I had the regulator replaced this morning and all is back to normal. I talked to the mechanic that looked at it the other day and he said that he didn't even smell fuel. It was funny because with the car sitting there today, that is about all that you could smell in their service lane. He said that he smelled it now. I guess this would be easy to miss. We were talking about it and I said I guess that with a leak that small, you could easily miss it on a fuel pressure test. The pressure would probably drop so slowly that you would have to monitor the pressure forever.

Oh well, it is fixed. Now to focus on my windshield that I replaced to fix a leak, had it installed by morons, and now it leaks even more on one side than before. Of course, I am wondering who the bigger moron is now. Them for installing everything wrong, or me for hiring them to do the job in the first place. :)

Nick
 
Good thing it was something simple, I had an similar issue on my 95' and it was the tank, no leaks or signs of dampness of drips ect. because the tank has a plastic liner inside. and the vapors escaped through the vent T near the opening of the tank and down through the 2 layers of steel.

and the pricing I believ on a NEW GM tank was $1900 yes almost 2 grand.. picked up a used one from vette2vette.com they are semi local and it was I think under $200!!

here is a link to pictures from that.. http://www.rickanthonymotorsports.net/phpBB2/viewtopic.php?t=48

-=Rick
 
I too am having a fuel smell lately, did a pressure test and a close inspection and the fuel injectors are leaking. Well the gaskets anyway. So anyway I bought the Accel injectors from Summit and got them in two days, great service btw. I'm installing them next weekend. Will keep my original injectors for the next owner.
 
I had the same problem on my '86 { hard start cured thread } I changed my vapor cannister and all the lines to it first. I still had the problem { not to mention the hard start } and I changed the line going into the vacuum cannister. Fixed,, no more gas smell. Before I changed the lines I looked at them very closely and everything seemed OK, but after I pulled them I started to notice that they were very dry/dead at the ends that slip onto the valves and connectors! Have you ever noticed any fuel smell when decellerating? If so I'll be you have a vacuum problem like I had. Good luck.
 

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