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History / OriginalityGot a question about 1982-1992 Camaro or Firebird history? Have a question about original parts, options, RPO codes, when something was available, or how to document your car? Those questions, answers, and much more!
I haven't been driving my car as much as I'd like to because of the gas smell and the boiling gas in the tank. Living in Florida and daily temps being over 90*, the gas boiling and pressure in the tank will build rather quickly. It appears that many other 3rd gen owners experience the same issue and a search on TGO shows that nobody has really determined an exact fix.
I removed my fuel tank vent valve and cleaned it really well. It appears to be working just fine. If I try to blow thru it, I can't and then it pops open and vents. It does this every time, so it's working.
I replaced the vapor canister purge valve and it didn't resolve the issue. A few years back, I replaced the gas cap with an NOS GM original, so I know it's correct.
Here's where the issue lies. If the problem is with the charcoal canister or the purge solenoid, I can't replace them. The solenoid appears to be sold together with the canister and the canister is discontinued. Has anybody found or know where I can get a solenoid? I would like to drive the car, but I won't until it's running correctly. Thanks
Fuel Tank Vent Valve
Vapor Canister purge Valve
Vapor Canister and Solenoid with red plug in center left of image.
Have you tried just disconnecting the evap can from the tank vent and letting it vent to atmosphere? I'm not suggesting that as a fix, but a diagnostic step. Because obviously if you still have a pressure build up with the evap can disconnected, it's not a evap problem.
The Evap parts for 88-92 are still available aftermarket, you could adapt to the later setup and no one would ever know. You could also eliminate the recirculation design of the stock setup, and just run the tank vapor line to a charcoal can, and it'd absorb the vapor/odors.
Personally, I'm guessing you could change the evap can and you'd still have the same problem. It shouldn't have anything to do with regulating the pressure in the tank. Isn't there a valve in the sending unit on the inside of the tank?
I've not tried disconnecting anything yet. I guess I can try this. I'll give it a shot, but won't I still smell the gas when driving because it's venting rather than being filtered by the canister?
Absolutely, but it should allow you to see if the tank still pressurizes without the canister connected. I'm sure the 87 service manual has a couple pages devoted to testing the valves, my manuals are all for the later cars and may not apply.
There should be a roll-over valve on the sending unit inside the tank. I want to say it's in the vapor line connected to the canister, but I can't find any mention of it in the service manuals. If the roll-over valve is inline with the evap canister, and if it's stuck closed for some reason, it could be the source of your issue.
Ok, just so I don't do something absolutely stupid, which exact connection should I remove for the vent? I haven't found any diagrams yet that are exactly as mine is set up, only similar. Here's what mine looks like. I'm thinking it's the lower line marked PCV. Just want to be sure. Thanks Drew.
I'd pull the hose right off the hard line at the bottom of the washer fluid tank, that way you're eliminating the entire Evap system, which should let the fuel vapor in the tank expand as needed. If the tank still pressurizes you know it's something between the open end of the hardline and the tank. If the tank stops pressurizing, your problem is in the Evap can system.
As I understand it, the first valve (the one not on the canister) controls when the tank can vent to the charcoal can. The other valve, and the solenoid control when the canister can vent to the engine. If you've already replaced the first valve, I would think the vapors should still vent into the can, just the other valve might be keeping them from venting back to the intake.
I want to say I've got a couple early charcoal cans somewhere in my spares, I just haven't seen them lately. I'll keep an eye out for one and let you know if I stumble across it. On my Brand-F project car, the charcoal can had to have the re-circulation hose disconnected when I got rid of the factory air cleaner box (K&N cone). Later I had to can (no pun intended) the charcoal canister altogether to make room for intercooler piping. For a few years now, the hose from the vent hardline just runs to atmosphere between the inner and outer fender. It's not EPA approved, but I never smell gas fumes.
Ok. I'll disconnect it at that location. Your troubleshooting options make perfect sense now that you've described it. I'll do it tomorrow and respond back with the results. Thanks
Scott we all seem to have this issue now. I've replaced everything on my formula and still have this issue on hot days. On cool days I can run the tank low with no issue, however on hot days I still have no luck. I firmly believe it is today's gas mix. I am at a total loss right now also.
So based on your argument, that explains why living in Minnesota, I never had a problem with their mandated use of ethanol in early 2000-2002. I moved to Florida, where it's obviously much warmer in the summer, and had no issues for many years because ethanol wasn't required. In 2008, ethanol became a state requirement. It was about this time that my fuel pump went out.
I have a picture of my odometer when the car turned 14k miles in January of '07. I took the car on the Hot Rod Power Tour in 2011 and had a little over 15k miles when we left. So in four years, I put a little over 1000 miles on the car. This would explain why I didn't notice these issues until I was on the Power Tour. During the Tour, they take you on back roads and country streets to "see" America. In heavy traffic areas like downtown Nashville and Indianapolis, the car stalled on me. I was required to wait awhile and it restarted. I could smell a heavy gas smell and that's when I noticed the fuel boiling in the tank. I didn't know why it stalled, so I turned around from Indy and headed home. The temps were close to 100* every day of the Tour and my only issues were in slower driving conditions. I replaced my gas cap when I got home because after driving the car, I couldn't get the gas cap secured, so I thought it was somehow defective. What I recently learned is that the gas was getting so hot, the filler neck was expanding, not allowing the gas cap to seat. This is all starting to make sense.
There is a gas station near me that sells 91 octane "pure" gas for $2.99/gal. I've been trying to fill up with that lately, but this last tank of gas is from another station with 10% ethanol. I will try Drew's suggestion for venting and see if that helps. After this tank is gone, I'll see what "pure" gas does.
I've been using 10% Ethanol since the mid-90's. I suppose it's possible that the ethanol in the fuel may have effected a plastic or rubber part, causing it to malfunction, but I'd be just as quick to blame it on low mileage and sitting for long periods of time. Either way, if a part has failed the damage is already done and changing fuels now isn't going to reverse the damage.
The rain finally stopped long enough for me to hike back in my personal junkyard to my spare fuel system. For the record, this tank/pump/sending unit is all from an R6P 1991 Formula LB9/5spd. R6P in the 1991 Firebird is approximately the same as G92 in a 1991 Z28.
Anyway, the vent to the charcoal can runs from the roll-over valve on the bottom side of the sending unit inside the tank. I don't have a way to test the valve, beyond pressurizing the hose off the sending unit. Doing so I could see the valve move, and air would enter the tank. I'm not sure what it'd do if pressurized the other way, since I don't have a great way to test it. However, seeing as how that valve is upstream of the charcoal can, it could be keeping your tank from venting if it's failed in some way.
The plastic breather on this one functions like you mention in your original post, at a certain pressure it vents. I'd be curious to know if it opens and at which point it opens under suction, but I don't have a vacuum pump handy to check. I would assume that either the breather or the gas cap have to allow air into the tank to allow for displacement of fuel, or the tank would crush like sucking the air out of a balloon.
Pics to show what I'm talking about, and just because, since it was already apart. These pics also show that this is an untouched assembly as it left the factory, including the fabled "1LE" "dual fuel pickup" and the "1LE" baffled fuel tank.
Update... I disconnected the vent line just between the tank and the purge valve. I drove the car in upper 80* temps today and didn't notice much temperature rise at the fuel filler neck. After about 20 minutes of driving and 10 minutes of idle, the gas cap came right off, there was no vacuum evacuation at the cap and the cap was easily reinstalled. I also noticed that my purge solenoid was so hot that I couldn't touch it. I was believing the issue could be the solenoid!
I turned the car off while chatting with a friend. I drove home at speeds that varied from 25-55, mostly at the 25-35 mph range (back road/neighborhood speed limits). I let the car idle again for about 10 minutes, all totalling about 35 minutes this time. In the garage, I could hear the gas gurgling and removing the cap, there was some pressure release, but not as much as I've been having. The tank is hot to the touch, as is the fuel filler neck, but I can easily replace the gas cap.
With the gas gurgling in the tank and the tank itself still extremely hot to the touch, my thought of the solenoid being the problem might be wrong. Now, the pressure build up wasn't nearly as bad as it has been, but it also wasn't 90*+ today either. I also didn't drive the car as far as I usually do. Should the fuel tank be getting hot? I don't see any reason why it should except for the fuel pump itself. I wonder if the issue is related to the quality of the materials used or an internal redesign of the new fuel pumps, compared to what was originally in the car.
Like everything else today, EPA and government regulations might have required something be changed and the side effects were not expected, but this is what we get now.
Another status update. I drove the car today about 40-45 miles in all traffic conditions. The temps are about 90* today and typical Florida humidity.
With the vent line open, I drove about 15 miles in slow, stop and go cruising. I had about 1/4 tank of gas left. Filled it up with 89 octane non-oxygenated gas. The cap came off without any hissing, the fuel filler neck was cool and the tank was warm.
Now, with a full tank of gas, I needed to drive! I stopped to get lunch after the majority of the drive, the tank was still hot, filler neck was warm and gas cap came off without any hissing sounds. I had about 27 miles on the new tank of gas at this point.
I reconnected the vent line, and drove about 12 miles home. The gas cap came off without any hissing and the tank was still warm! I could still smell gas really strong in the garage. I don't think my drive test did anything other than blow out the cobwebs!!!!
Scott I am having similar issues except I have major pressure in the tank and hot gas. If I open the gas cap I get a lot of pressure and can feel the heat. if I don't release the cap after a drive and it sits in the garage I will hear a high pitch whine... from the cap I think or the vent valve?The car has a hard time staying at idle due to this and will die at lights. If you open the cap and drive it will drive for a while then have issues after a while. I am concerned since I have a long drive (80 miles) in aug with my son to a car show and the last thing i need is an explosion due to hot gas if I dont stop it will run but again boiling like you have. it looks like to change the pump it a bear of a job... https://www.thirdgen.org/forums/tech...placement.html
I do find if I put in some lucas fuel system cleaner it does well for about half a tank then starts having issues again... it seems like a short term fix.
Last edited by IMissMy86TA; 06-01-2015 at 09:24 AM.
I went to Sunoco yesterday with my 88 and put in 11 gallons of 93 octane to fill it. When I took the cap off a huge amount of venting occurred. This was after driving just 8 miles.Temp outside was 85 and of course humid in Bama.
I have used Pure, ethanol free and could tell no difference other than while pumping it, it smelled like real gas!
IDK, it seems this car did this from day one. I do get the smell of strong odor when it sits in the garage after a drive.
I had the same issue with my 85 bird. One day i was driving around, stopped got out and was chatting with the car running and all of the sudden gas started coming out from the evap canister. Tank had alot of pressure in it, took the sending unit out and the rollover valve was stuck. I cleaned it so it wasnt stuck anymore and havent had a problem since. Hope this helps.
Ok, I'm still working on this. I removed the vent line again. This time, I disconnected the entire setup, vacuum line and all. Started the car and the CEL was on. So, I reconnected the vent line to the charcoal canister and reconnected the vacuum line. I only left the hose disconnected from the hard line. I drove around a bit in 90*+ weather, but didn't go far. I got to my destination and grabbed the gas cap, no hissing and no pressure build. I stayed about 45 minutes.
As I was leaving, the CEL came on again. I reconnected the vent line and drove home. I get home and there is gas all down the side of the car from the filler cap. It was on tight! I removed it with no hissing or pressure buildup. Again, this was a wasted test trip. I have 3/4 tank of gas now. I guess I need to disconnect the vent line and just drive it in traffic and get it really hot and see what happens.
You are not alone with this problem.
I too started off by thinking cap was the problem.
Had a gas tank spew a couple weeks ago do a good number on my paint.
My band-aid so far has been to just not fill more than 3/4 tank.
Have not had issues since doing this and I have driven longer trips on much hotter days using ethanol gas from same vendor as before.
But ... it is also possible that I have an intermittent problem that is just lying in wait to bite me again when I least suspect it.
Question for those who have messed with the roll over valve in tank:
By the way it operates and potential way it could stick, do you think it is possible to back-flush some fuel system cleaner through the line at the canister? If we can find a way to do it do you think it would help?
I have a 92 Z28 that is 100 percent original downto the tires with 21k. I have owned it since day one. I have all the same issues with the hissing tank and gas smell So after checking all the same things you guys did like the evap and restrictions in the lines and so on with no issues I decided to go out and got a infored thermometer and start taking temps. Started with the car cold. It was 72 deg out..engine, fuel rail, tank and lines all at 72 deg. Started the car let it get to operating temp. Measured the temp at the thomostat outlet, fuel rail between the runners, the fuel line at the filter to the eng and the rerun line next to the filter so I could get a clear read on fuel temps away from the engine compartment. Once the engine hit op temp the rail was around 110 deg with the eng at 195. Once the eng got hot after 20 mins or so the fuel rail hit 145 deg..... return fuel was consistently 15 warmer then the fuel going to the engine from the tank...... and both temps rose the longer the engine ran....so after 30 mins of run time the fuel rail was at a constant 145 deg, the return to the tank was about 130 and the tank rose from 72 deg to 120deg. That is when the Hissing and gas smell started. The longer the engine ran the with the rail at 140 deg the return line fuel temps rose. At about 30 mins run time the return line was at 130 deg."...So... I think the stock pump is about 15 gallons an hour so at a full tank it will push the entire tank thru the 140 deg fuel rail in a hour heating the fuel. Half tank 2x an hour......the warmer the day the more the engine heats the fuel and the worse it is. Thinking with today's ethenal fuels with higher volatility this is now an issue where it may not have been back in the day. Any of you have a thermometer and want to see if you see the same? Your ideas? I'm pretty sure there is nothing wrong mechanically with the he car as everything works per the service manual. It has always hissed but I the last 10 years or so it's way worse. About the time ethenal fuels started..hmmmmm. .thinking the design of the TPI and the high fuel rail temps is super heating the fuel. Pump is original. Out of ideas
Well I seem to have cured my hot gas / vapor issue. While I do believe today's fuel is most of the problem, as well as our TPI design along with high under the hood temps. So I took some extra steps to combat it. My AC compressor was on its way out and the condenser cooling fins looked damaged from years of road abuse so I deleted the system, as well as the smog. I added a cooler fan switch from a Grand National, a 180 stat, and
new radiator. Also part of my problem was all the crap packed between the radiator and condenser, along with damaged cooling fins impeding air flow. Went out a few long drives, one was an hour plus of hard driving in traffic. No pump whine, gas tank cool to the touch, and a slight pressure release after opening the gas cap. Best part is plugs will be a breeze to change and when I do my valve stem seals next the job will go much quicker. Car runs much cooler now too.
05-23-2015, 01:46 PM
"1LE" "dual fuel pickup" and the "1LE" baffled fuel tank. 
if I dont stop it will run but again boiling like you have. it looks like to change the pump it a bear of a job...
