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1995 GMC Sonoma fuel leak
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SuzyPooch
User
Feb 8, 2014, 5:29 PM
Post #1 of 17
(2869 views)
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1995 GMC Sonoma fuel leak
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First off a BIG thanks to all that contribute here and for your time and expertise.! I'm a Newbie on this forum but thought I'd ask my question and see who/what comes up. THANKS again for your help.!
I've got a 1995 GMC Sonoma SL model with a 2.2L engine, auto trans, 196,000 miles. This one uses OBD2 scanner.
Currently I have some kind of fuel leak under the hood when the engine has been running for a while and then shut down. The smell alone will knock you over and it comes from the front right side of the vehicle (when sitting in the driver's seat). You can smell raw gasoline even with the hood closed along the passenger's side of the hood outside of the vehicle but not in the cab. I cannot see any kind of wet fluid leak in the areas where all 3 fuel lines connect to the fuel rail, bottom of the air intake plenum or the pressure regulator valve which has been replaced. I have traced all fuel lines coming from the tank including all connections from the tank forward, fuel filter, associated rubber hoses and gas line fittings under the hood, no leaks anywheres to be found so far.
I've checked all the vacuum hoses I can reach and all of them are tight. This vehicle runs and starts great so I'm thinking if there were unconnected vacuum hoses something would indicate that.
The engine runs good and I get 32.4 mpg using real gasoline (not the alcohol tainted mix) on the highway and a solid 24 mpg in the city. NO trouble codes from computer, NO warning lights illuminated. The vehicle runs like a rocket, starts normally even in low teens temps and runs smoothly even when cold but only at idle speeds until the temp comes up on the gage (aluminum head caution), and I don't notice any gas smell when driving or with the hood up when the engine is running--ONLY after the engine has run for a while and then shut off do I get the gas smell.
I've located the gas smell somewheres next to or even between the fuel injectors and the air intake plenum. Again...NO visible leaks of any kind of fluid in these areas, nothing dripping down along the side of the engine or on the ground, NO evidence of prior fluid leaking such as a dirty dried up trail where fluid used to be. All electrical plugs and wires are tight including numerous ground straps that I've located so far, nothing indicating something came loose or is worn out. I bought this vehicle used some 5 months ago and so far this is the most serious ailment I've noticed, although I've replaced many parts in multiple systems since buying it.
Right now I'm hesitant to drive this vehicle until I can find the problem and get it fixed. No sense in getting roasted or blown into little bitty pieces as that would mess up anyone's day for sure.
I have a Haines maintenance manual but it doesn't clearly show the fuel rail assembly where the injectors are located and isn't as good as the OEM Tech manuals the big shops use. I'd prefer to fix this myself if possible since I've been doing general automotive repairs for the last 48 years.
Any suggestions.?
(This post was edited by SuzyPooch on Feb 8, 2014, 6:50 PM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 8, 2014, 8:55 PM
Post #2 of 17
(2841 views)
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Re: 1995 GMC Sonoma fuel leak
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Have you inspected the EVAP system and vapor lines?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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SuzyPooch
User
Feb 8, 2014, 9:43 PM
Post #3 of 17
(2837 views)
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Re: 1995 GMC Sonoma fuel leak
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No I haven't as I didn't think it pertains to a gasoline leak. I'll try to get to that tomorrow and see what gives. THANKS
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 8, 2014, 9:48 PM
Post #4 of 17
(2835 views)
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Re: 1995 GMC Sonoma fuel leak
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The vapor lines carry fumes from the fuel tank which are stored in the charcoal canister. The canister is purged as the engine is running, so if you have vapor lines leaking, your going to smell fuel vapors. Other than that, your going to have to visually look for the fuel leak. We can't help you with that because we aren't there to see it. You may need a second pair of eyes.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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SuzyPooch
User
Feb 8, 2014, 9:53 PM
Post #5 of 17
(2829 views)
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Re: 1995 GMC Sonoma fuel leak
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DSignals.....you may have very well found my problem. I just checked in the Haines manual and sure enough it does indicate if theres a problem with the Evap cannister or the lines there would be a strong smell of gas. I WILL check into this on Sunday. Thanks very much.! SP
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 8, 2014, 9:57 PM
Post #6 of 17
(2825 views)
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Re: 1995 GMC Sonoma fuel leak
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Let us know what you find out. 
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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SuzyPooch
User
Feb 8, 2014, 10:03 PM
Post #7 of 17
(2822 views)
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Re: 1995 GMC Sonoma fuel leak
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So far I've had several sets of eyes all looking at the same time with bright LED shop lights but so far no one has seen any drips or wetness. It may very well be the Evap cannister or it's associated lines as the former owners didn't take care of this one at all. After 19+ years of use on this vehicle it still runs great and it's gas mileage is better than my brother's 2 year old Ford Fusion. I'd jump for joy if its the Evap system verses a few hours of work to take things apart just to get to the fuel injectors to replace all their O-rings. I didn't even think of the Evap system but am still learning the various systems on this model of truck. Now I wished I had a truck that was pre-fuel injection/non-computer controlled so repairs would be easier and possibly cheaper....
THANKS MUCH...!! IF this solves the problem instead of giving you a few gold stars I'll just give you the entire package.
SP
(This post was edited by SuzyPooch on Feb 8, 2014, 10:15 PM)
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SuzyPooch
User
Feb 8, 2014, 10:05 PM
Post #8 of 17
(2820 views)
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Re: 1995 GMC Sonoma fuel leak
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Will do and THANKS so much.!
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SuzyPooch
User
Feb 9, 2014, 12:07 PM
Post #9 of 17
(2804 views)
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Re: 1995 GMC Sonoma fuel leak
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I spent 3 hours this morning inspecting the EVAP system and it's related vapor lines. Since I live in an apartment complex that doesn't allow us to work on our vehicles I'll have to get the vehicle to a friend's house maybe mid to late week after our ice/snow comes and goes. I could feel the outlets from the cannister and it "feels" like all three hoses are connected tight to the cannister but I can't actually see the outlets. I'll have to remove the cannister from it's bracket to see further. I did trace the vapor lines as far as I could follow and they start out as rubber lines at the cannister then change to metal lines mounted on top of the left frame rail, back to rubber about midway then back to metal lines going over the tranny and finally back to rubber lines coming under the hood. I think I could design something better than that and I'm not even an engineer.!
I was surprised to see one of the vapor lines is connected to the gas filler neck....I thought it would be connected to the top of the gas tank instead. This is a rubber line and its tight and still in good shape.
I wiggled all the lines and found one that was partially pulling off it's outlet mount under the hood. I pushed it back on as far as it would go on it's outlet. I then did a test drive and upon returning this time I couldn't smell any gas vapor in the areas I described in my original post. Still NO gas smell at all under the hood so not sure if by wiggling the lines along their length that did any good but at least for now...NO gas smell anywheres.!
One last question for you...DOES the EVAP cannister ever wear out and need replacing.? My local O'Reilly parts store has a new one for $131 plus Texas tax but I wouldn't replace it unless its absolutely the problem. This vehicle is now 19 years and 3 months old. I'll keeping watching and smelling and maybe this time I won't have to replace another expensive part. Might contact you at the end of this week with any further developments.
THANKS AGAIN for all your help on this.!! SP 
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 9, 2014, 12:23 PM
Post #10 of 17
(2798 views)
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Re: 1995 GMC Sonoma fuel leak
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Normally no, vapor cannisters usually don't wear out. They can crack if damaged and/or become saturated with liquid fuel if you have a liquid vapor separator issue in the fuel tank. They could also leak charcoal into the lines and cause restrictions, but I have never seen that happen on those style of cannister.
One tool that works well for finding vapor leaks in a sealed EVAP system is an EVAP smoke machine. You can also separate the system into sections and use a hand held vacuum/pressure pump to determine if you have a leak in some part of the section your testing. To check the canister for raw fuel contamination, you'll have to remove it and turn it upside down to see if fuel pours out.
Liquid fuel contamination may be unlikely because it would turn on the check engine light for rich codes as the engine controller is purging the canister. The cannister also has a port to allow fresh air in when the system is being purged. It is possible for the canister to become over saturated with fumes if the EVAP system isn't purged due to a purging issue. Older systems, like that one, were not monitored for purge flow, so you wouldn't know if the EVAP system was working or not.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 9, 2014, 12:32 PM)
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SuzyPooch
User
Feb 9, 2014, 12:33 PM
Post #11 of 17
(2787 views)
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Re: 1995 GMC Sonoma fuel leak
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OK..great and thanks again. Maybe that one vapor line that I found under the hood this morning was the culprit but I'm not sure. At least for now I'm a little more relaxed in that the gas smell wasn't present after returning back home. The vehicle still runs just fine although I still have more parts to replace in the coming months.
And do we still believe that when gasoline wants to ignite its usually the vapors that light first verses actual liquid gas.? THIS is what got my attention pronto on this leak/smell problem. Last thing I need is for this to catch fire then before I can get out the whole thing goes up.
THANKS MUCH for your time.....I'll advise later on this week. SP
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 9, 2014, 12:41 PM
Post #12 of 17
(2782 views)
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Re: 1995 GMC Sonoma fuel leak
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Your welcome
Yep, if the vapors are concentrated enough and you have an ignition source, they'll ignite. Probably wouldn't hurt to purchase a fire extinguisher for your vehicle. Every vehicle should have one.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 9, 2014, 12:42 PM)
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SuzyPooch
User
Feb 9, 2014, 12:50 PM
Post #13 of 17
(2773 views)
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Re: 1995 GMC Sonoma fuel leak
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Yep....in my profession of Aviation we have the same deal. The fumes are quick to ignite then they follow any liquid fuel to the source and its a whale of a BBQ in a hurry. Step in any jet fuel and it'll melt the rubber soles of your boots or tennis shoes. Nasty stuff.
I'll keep after this and may remove the cannister Thursday and see if any liquid gas pours out of it. I'd like to physically check those vapor line connections on the cannister to make sure. One bolt on the bracket but its a tight sqeeze for my fat fingers. I'll also check the fresh air inlet and see if that is partially clogged.
THANKS sooooooo much for your time and thoughts on this.!! GOOD thing I found this forum as its a big help to have a second or third opinion. Guess I have more studying in the maintenance manual to get done as IF I can keep this vehicle healthy its a good cheap form of transportation once I can get some
needed older parts replaced like the engine's cooling system and the rear brakes. These are next to be replaced.. Have a good week coming up.! SP 
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SuzyPooch
User
Feb 9, 2014, 12:54 PM
Post #14 of 17
(2766 views)
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Re: 1995 GMC Sonoma fuel leak
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Perfect for everyone. I've got an ABC rated one in the vehicle and I hope I never have to use it but better to have it and not need it, than to not have it and then need it. Great idea for sure. THANKS.!!
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SuzyPooch
User
Feb 9, 2014, 5:38 PM
Post #15 of 17
(2751 views)
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Re: 1995 GMC Sonoma fuel leak
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DS..I'll get to my truck this coming Wednesday instead of Thursday then hollar back so you can close out this post.
THANKS MUCH for your help. I am a more "informed and corrected" Sonoma owner now and hopefully can make it better as time goes along. This vehicle was a mess when I first bought it but now its doing way better and the work I've done to it brought the gas mileage way up and hopefully it's value as well.
THANKS so much for being out here for all of us..!!
Pete (SP)
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SuzyPooch
User
Feb 10, 2014, 1:02 PM
Post #16 of 17
(2739 views)
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Re: 1995 GMC Sonoma fuel leak
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DS...I had a slow day today at work so I pulled my truck into the hanger and I took the left rear wheel off to get to the EVAP cannister better. All three of the line connections are tight and the air vent hole on top is good to go after I wiggled a wire into it to clean out any dirt. The cannister itself was dirty but after wiping it off I didn't see any cracks, dents or otherwise bad stuff. I also turned it upside down but no gas or liquid came out. One of the A&P mechanics stopped by an O'reilly parts store on his way back and picked up a new Evap cannister purge control value ($31) and I installed it on the truck then went and drove it for a while. Came back and now theres absolutely NO gas smell anyplace under the hood or along either side of the vehicle. I think this might have been the original cause of the gas oder I was smelling.
You can close out this post and thanks to your suggestion I believe this issue is resolved. GOOD SHOW for sure.!! So....now you have earned yourself the entire package of gold stars and I thank you very kindly for your time.!!
SP
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 10, 2014, 2:24 PM
Post #17 of 17
(2732 views)
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Re: 1995 GMC Sonoma fuel leak
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Closed at OP request.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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