alan91z28

Like many people, I have experienced during hot days issues with several of my 3rd gens (I have many as noted in my sig)...

- 1988 Camaro completely rebuilt last year including new GM ZZ5 crate engine, tpi top end components, fuel, evap, etc, etc... now will not take fuel into tank except as a dribble without spilling all over, obviously not venting

- 1988 Trans AM with 30K miles original 5.0 TPI 5 speed... on hot days once warmed up will stumble / stall at stop and has extremely loud fuel pump whine

- 1988 Camaro 75K miles with original 2.8 MPFI auto... on hot days will stall at stop signs or sometimes even coasting at low speeds... have to put in neutral while coasting / stopping to try and avoid stalling

All of these 3rd gens also have common issue of significant fuel pressure in tank on warm days as exhibited by large hot pressure exiting tank when removing fuel cap

Needless to say it is no fun worrying about this and I would even get to the point of not driving one of these when hot and picking one of my other 3rd gens that didn't seem to have the issue

Since I have a large amount of 3rd gens I can also say that while I do believe today's fuel might be causing issues with the ethanol, it is more of an aggravator I believe as I have several of my 3rd gens with the same fuel that don't have the problem

Also while having a strong new fuel pump clearly helps, even on my newly rebuilt 1988 with new USA walboro while not stalling has the fuel fill issue now and on occasion can be hard to start immediately after a warm shutdown on a hot day

Therefore I concentrated on how do I avoid pressure build up in the tank, in my view should avoid all these issues on vapor lock, fuel fill issues, etc

While I know that if I went through one by one I eventually would find the canister or ECU driver or check valve, or on and on that if corrected should resolve it... however what put me over the top was my new rebuild that already has issues... I have had enough of this so I went on to try something else

Note I was planning on driving all summer on what I have done, but since results on all three 3rd gens have been completely positive I figured I would share what I have done

Also I live in NW PA so we don't have 100 deg days, but pretty much 80 deg and up I was having the issues...

You are responsible for your own 3rd gen so I am not telling you to do this if you have this issue, you decide for yourself

alan91z28

The solution I drove to had the objective of keeping the Fuel Tank Pressure the same as atmosphere... ie no pressure difference. When you take the fuel cap off you hear / feel nothing

To do this I needed to have a way of letting both air in and air out

Also I wanted to do it in a way that I felt was safe

After researching venting on older car fuel tanks and retrofit tanks I found a nice vent valve made by Tanks. It is their VVR valve and available from summit for $15. This valve allows air in and out and also has a roll over check ball

I decided to eliminate the "UFO" valve and mount this vent in place. The pics attached show how easy it is to do. I only needed to drill open the UFO bracket slightly with a step drill to mount this new vent

A 3/8" fuel line hose connects the new vent to the original "UFO" hard line coming from the tank

Remember this hard line is right at the top of the tank, ie does not extend into the fuel supply in the tank

alan91z28

To date I have installed this on all three of my "troubled" hot weather 3rd gens

With about 3 weeks of run time I now have had zero issues on all three 3rd gens that I equipped with this modification

- No fuel up problems
- No cut outs while coasting at low speeds
- No stalling at stops.
- No whining fuel pump
- No need to try and shift into neutral and keep the foot on the gas in attempt to avoid stalls like previously...

In fact I have now gotten to the point I have intentionally been trying to make a stall happen by trying to do a lot of start stops in low speed traffic (I use to do everything to avoid this traffic on hot days)

Also no matter how hot it is, how long I drive, etc, taking the cap off the fuel fill immediately after stopping results in absolutely nothing... ie no pressure

My testing has been limited but positive so I share this earlier than I was planning to for the sake of knowledge to this frustrating issue

Also I am sure someone will want to know about do I get any fuel smell, etc... to date I have not had this issue either. While I don't expect it to be vapor free as obviously it is breathing, fuel vapor is also heavier than air so unless there is a fuel pressure difference it isn't going to just naturally be letting vapor escape.

chazman

iTrader: (4)

Interesting, thanks .

fervernt

Just wanna add my 2 cents on this, because I had the same problem for awhile, stalling/fuel pump whine on hot days. I had a new fuel pump put in due to low fuel pressure, started making a lot of noise within a couple weeks. Had it warranteed out for a new one. Same thing happened to that one a couple weeks after. In that time I found out my 91 had a recall out for the gas tank filler neck having pinhole cracks in it. Went and had the gas tank recall taken care of, completely new tank. Then had the new pump put in. This was 4 years ago, hasn't been an issue since the new tank went in. The interesting thing to me is that most people say the problem seems to be excessive tank pressure, but my new tank still does the whole hot fumes and pressure on a hot day when I take the cap off. But no drivability issues or fuel pump noise. I think the cracks in the neck causing it to depressurize was actually causing the problem.

greenyone

iTrader: (1)

Can I buy you a beer? I've been all over the Grainger and McMaster catalogs looking for something like this to solve the same problem. With all of the googling of tank venting I can't believe I never came across an actual automotive part solution. I currently have 2 gas caps. One for hot weather with tiny holes drilled in it and another without for the colder weather. I guess after this fix I can toss the modified cap.

Bob88GTA

iTrader: (2)

Thanks Alan
Well........sounds really promising. I cleaned my original tank valve last weekend and it was found to be stuck closed. I then added 14gallons of 90 octane pure gasoline from Texaco. Been driving all week, 170 miles so far, in 90+ heat. No abnormal issues,fumes, pressure, or any of the problems that we all been seaching for solutions.
IDK.......I'll order one of those from summit and try it.........it sure cant hurt!
Thanks for your tip.
Now.....go buy a beer on me!!

thtanner

iTrader: (1)

The car does this by design, unless you ripped out the smog stuff, capped the vent, or have some faulty components.

Valve under the tank: lets air into the tank to prevent negative pressure. If venting into the tank is not functional you can clean that valve, or add a vented gas gap (they only let air in).

Vent to charcoal canister: tank then vents positive pressure to the charcoal canister. There is a valve in the engine compartment that opens after a few PSI to allow the pressure to release. If it is not venting properly I would check the valve by the charcoal canister, verify the canister is not clogged (can blow through it easily), and ensure the vent line running from the back of the car is not clogged.

I have a new fuel tank, all my lines/vents are clean, and I can drive through any temperature without building up too much pressure. There is always positive pressure, which is by design, just not an alarming amount.

Bob88GTA

iTrader: (2)

thtanner...you're 50% correct.

Those valves typically serve TWO purposes. 1. As a vacuum relief- allowing air into the tank if a vacuum should develop, like you mentioned, and 2, as a tank pressure control valve- holding in some pressure to work the charcoal canister system, but with an overload valve to allow it to vent to atmosphere if that pressure becomes excessive, around 6-7psi, it opens so as not to damage or rupture the thin sheet metal gas tank. I had mine apart last weekend and tested it both ways...it's working now.

EDGE

Thanks for this. Just ordered it. I've been dealing with this for years. Been trouble free for two years now since all the mods and repairs but I still occasionally build pressure so I figure if this works, then why not. I know the UFO works but It may be getting old and sticking.

thtanner

iTrader: (1)

If you want to be pedantic I would say I was 66% correct overall, but I guess D's don't count anymore.

Honestly did not know they acted as a fail-safe as well. Great info

So, in short, as long as stock components are in working order, you should not experience an over-pressure situation in the tank.

alan91z28

Yes this is correct, my point though in doing this is I have had enough of these issues and am aiming for correction of the issue once and for all... a couple things that pushed me over the edge on this as I mentioned:
- my all newly rebuilt '88 began getting symptoms only a year after full rebuild
- you can't buy all new components anymore, ie the UFO valve you need to try and clean, I have done several of these but the plastic is fragile
- I believe today's gas mix is making it worse if you have issues already and trying to buy pure 100% gasoline in my area without ethanol is hard to find

while again I think it needs more time, the vent I added is simple and eliminates pressure and reduces heat without really compromising anything in my view except some direct venting vs going through the charcoal can back to the throttle body... high tank pressure is going to affect the fuel flow/pressure function of the pump and regulator so my desire was to fully eliminate that potential

thanks for the feedback, if anyone else tries it keep us posted on your results as I will with my modified 3rd gens

thtanner

iTrader: (1)

Just a note for posterity, since this thread is likely to be useful for others in the future..

This would cause a smog test failure in California, due to the EVAP test. (boo).

I don't know how much PSI is required to pass...

alan91z28

while of course just from an academic standpoint i would speculate a piece of duct tape temporarily put in place on the vent would resolve this unfortunate lack of practical discretion by CA on our classic 3rd gens!

alan91z28

just a quick update, it has been very hot and muggy (relative to my neck of the woods) all week and in particular over the past couple of days.

i have driven all 3 of my modded 3rd gens during this time with good performance out of all three. i have been trying to go out of my way to really be in stop and go during this time to get the engine temps up and no issues so far... on a day like today i would have been stalling all over coming to a stop without trying

alan91z28

i have had continued good success with this with no recurring issues to date on any of the 3 camaros i have installed this on.

if anyone else has tried this i would be interested in hearing your results

EDGE

I've since installed the new valve and have zero pressure issues in the tank, even on the hottest days. My sending unit is new, and so is my charcoal canister. Prior to this my tank was building pressure but since repairs to vacuum control lines the pressure wasn't to the point of blowing off the gas cap as it once was. But I was noticing on the really hot days there was more pressure than there should be. A good 3 second release of air when removing the cap. And hot air at that! Since this new Summit valve I now have none. I don't know if it's in my head, but I swear the car is running noticeably better. The acceleration has improved. At least that's what it feels like. I don't know what this new valve releases at or if it's just open all the time. Regardless, car seems to run better now. There is no way there should ever be a defined blast from the gas tank when removing the cap. I know of no other car that does that. Like I said, it was better after I did the repairs prior to this new valve, but I believe there was still to much pressure in there.

greenyone

iTrader: (1)

It's a tip-over valve, so it's open as long as it's oriented in the upright position. I put one in too and have ad zero issues since. I do sometimes notice a bit of fuel smell from the rear drivers wheel well where it's venting, but it's not any more noticeable than one of my old carb cars.

Honestly I think the main point of failure here is the vent valve that we are replacing with this tip over valve. I've tried two and get inconsistent results from both. I think the issue is that flimsy little plastic valve can stick sometimes depending on things like heat and humidity. Taking them apart and cleaning them sometimes seems to work from what I've read here on TGO, but perhaps they are just old and slightly deformed and somewhat past the point of working as originally intended.

EDGE

I think the idea of the old valve was to permit a certain amount of head pressure in the tank. A little bit is good as it serves to help control slosh and aid the pump a little. Problem is when it becomes excessive it starts to cavitate. That's ultimately what is causing the failure.

battman

iTrader: (2)

I'm going to give the tank vent a try. I went out for a cruise yesterday in my 88 GTA and the pump was whining most of the trip and when I was about 4 miles from my house the engine just shut down completely with no warning. I removed the gas cap and it was under a lot of pressure.

Thanks for the info on the vent!

Camaro86IrocZ

iTrader: (1)

The only problem I see is that they say to not (copied and pasted) -- Creating a trap within the vent line between the tank and vent valve. “When routing the vent line from the tank to the vent valve you must avoid running the vent line down and then back up again,” Somerville said. “Like a P-trap under a sink, this is a place that condensation or fuel can become trapped in the line. This trap will then block off your vent line and your tank will build pressure or vacuum until there is enough pressure to purge the vent which will cause gas and/or odor to come from the vent line.”

Why wouldn't simply drilling a small vent hole in the Gas Cap not do the same thing?

Bob88GTA

iTrader: (2)

[QUOTE=Bob88GTA;6066080]Thanks Alan
I cleaned my original tank valve last weekend and it was found to be stuck closed. I then added 14gallons of 90 octane pure gasoline from Texaco. Been driving all week, 170 miles so far, in 90+ heat. No abnormal issues,fumes, pressure, or any of the problems that we all been seaching for solutions.

UPDATE.......It's been 3 weeks since cleaning the vent, and running 90 Octane Pure Non-Ethanol Fuel.

No issues. and its been freak'n hot and humid here.
I think it's a combo of vent valve and Pure Gas. I like the results!

thtanner

iTrader: (1)

It would, but provide no protection from gas spillage in a roll-over.

The valve he used closes in the event of that, making it safer.

battman

iTrader: (2)

[QUOTE=Bob88GTA;6072920]Bob, Were you building a lot of pressure in your tank during hot days like this?

Do you think it was more pressure or fuel related in your case?

This problem sucks..

Bob88GTA

iTrader: (2)

It was building a lot of pressure. Then I cleaned the valve and been running 100% Pure Gas and it's been fine

The problem to me seems worse since the ethanol gas was introduced. I drove my 88 GTA in the California Mojave Desert for 20 years, on non-ethanol fuel, and NEVER had this kind of pressure. I had a little when I took the cap off, and I mean a little. Then moved here 7 years ago and been running this 10% added Ethanol, and I get pressure build up. So, I changed to Pure real gas and seems to me the issue is 75% better.

I could be crazy too! IDK..

alan91z28

yes I did also consider this, but I don't think it is really much of an issue. as long as you don't have much of trap even if you get something to settle in that area the pressure is going to evacuate it. if you think about it the "trap" in the standard evap line is much more significant than the way I ran this

so far so good, been giving these 3 that I modified good workouts and no issues to date including never having any pressure taking off the cap anymore

Bob88GTA

iTrader: (2)

We will be fighting this forever. Here's the thing......when I bought this 3rg gen new in 88, it had no issue. GM did not put "vented or drilled holes" in the gas cap. The car ran fine. The ONLY thing that changed was the added Ethenol in the gas. It was THEN that I personally started having the issue. Just my nickle!

battman

iTrader: (2)

Well I got my new Walbro pump installed and have been driving it for over 250 miles today. Driving conditions were mixed stop and go traffic and highway all with AC on and had absolutely no problems whatsoever with fuel delivery with 90°+ outside Temps.

Before the pump change I couldn't make a thirty mile trip during the day without fuel delivery problems.. I'm keeping my fingers crossed and hoping this fixes it permanently.

ZZ42Fast

iTrader: (2)

Thinking of doing this mod, thanks Alan.

I have serious tank pressure and so am thinking of this or cleaning out the ufo valve.

ZZ42Fast

iTrader: (2)

I have now also done this fantastic mod. No more worrying about the plastic UFO valve failing again. Thanks!

Swingblade

Well, I was putting a new sending unit in my tank this week and saw that my vent valve is completely gone! I guess whoever owned this car before me took it off and failed to put it back on, the hose is still there... Ordered the VVR valve since that is one of my only options at this point.

OddJack

iTrader: (1)

Nobody answered the question why not using a vented tank cap or drill a hole through it.

chazman

iTrader: (4)

I tried a vented cap on my '85. After 40 minutes of driving or fuel level below half the pump still screams.


I haven't removed and inspected/cleaned my vent valve yet.

GeneralDisorder

iTrader: (1)

The vent valve on mine was brittle and cracking. I just tossed it. Originally had the intention of finding something to serve that purpose. Never got around to it. The open line doesn't seem to be a problem. Nothing is going to get in there unless it crawls up the hose and into the vent pipe. Mine has "gone missing for several years now. To no detrimental effect. I plan on leaving it that way.

All my canister junk and purge junk is also deleted. Rubbish.....

Surprise....... I have no issues. And a cleaner engine bay.

GD

scottmoyer

The vent valve is not a purge valve. It's a one way valve to allow air in, but not allow vapor out. The vapor is supposed to be routed up to the charcoal canister in the engine compartment. So, by you not having the valve, you are intaking air and venting through that hose. You also don't have a vapor canister any longer, so your tank is venting to atmosphere.

For those of us with original cars that want to keep it original in appearance, we can't do what you did.

battman

iTrader: (2)

[QUOTE=chazman;6145560]I tried a vented cap on my '85. After 40 minutes of driving or fuel level below half the pump still screams.

Same here, vented cap does nothing..

Bob88GTA

iTrader: (2)

Scott..As mentioned MANY times before, it's a 2 way valve. Not being the "correction police" Just mentioning it

scottmoyer

Ok, let me be specific then. The valve is not a vent valve in that it's open to the air to vent fumes under the car. It's primary operation is to allow air in to displace the fuel that gets pumped out. The "venting" of the tank is via the charcoal canister under the hood. The valve has a simple feature built in for excessive pressure and will allow pressure out, but only under certain circumstances. Under normal operation, it's a one way valve to let air in.

GeneralDisorder

iTrader: (1)

I get what you are saying but who is going to look up there above the rear axle? The original valve is discontinued. Given that it would be trivial to swap *back* to stock (assuming you could find one) why not just keep the stock one under the stairs. It will stop deteriorating if it's not in operation and then when you want to turn the car into a museum piece then put it back on and park it on some carpet.

Also - life is WAY too short to stay stock. Even when these cars were in production GM was continually updating parts and changing things to address problems. Now that's our job. If you can't drive the thing or enjoy it for the sake of it being exactly as shipped from the manufacturer then what's the point?

GD

scottmoyer

Life isn't too short to remain stock if that's what you enjoy. Who said we can't enjoy a car for what it was originally?

GeneralDisorder

iTrader: (1)

But does this valve, that no one will ever see, destroy the essence of "what the car is"? If it solves a problem, and I would argue that the discontinued valve IS a problem, and allows the vehicle to still be enjoyed.....

Original parts for the sake of original parts is fine unless they are flawed in some fundamental way. Reliving the 1980's of discontinued plastic emissions equipment is like.... complete torture.

There's like a whole world of sunshine, hot babes, and cool cars to enjoy. Worrying about having the factory plastic emissions valve seems kinda silly doesn't it?

I'm a mechanic, machinist, shop owner..... as such I guess my perspective is just different. Original appearance is all well and good and I understand that. But original function is sometimes just not worth the trouble or no longer applicable to the car's modern life.

Perfect example - I have a 1956 Buick Roadmaster. The factory generator is not suitable to its life in parades, car shows, and other slow speed operation. Not to mention traffic. So it has an alternator the looks like a generator. Numbers matching replica nameplate, etc. From a company called Genernator. Sometimes you just need to put some modern technology in play.

GD

scottmoyer

This thread is not the place to argue the details you are mentioning, but I have to follow up with the response that I never said that removing this valve under the car is a problem. I said that people maintaining originality can't do what you did. You said you removed all the "canister junk and purge junk". I was referring to that! Can we get this back on topic?

GeneralDisorder

iTrader: (1)

I understand what you mean. I did say that and yes it would alter the under hood appearance.

Personally I would "delete" it regardless if it caused a problem. Just leave the stuff for decoration, shove dowels into the vacuum lines and hook them back up. Leave the bits and bobs for decoration and silently delete their function.

There's ways to accomplish both. Just takes a little ingenuity.

GD

NoEmissions84TA

iTrader: (1)

I agree with the way you think. Not just this post, but many others.

alan91z28

so far my experience continues to be very good with this mod on my F bodies

if you do not want to do this mod and what to remain stock it is essential that you have the UFO valve and the valves by the vapor canister along with the associated vacuum lines, canister solenoid, vapor fuel lines, etc all in good working order. if everything is working the system will work, i have done that too-

i restored my first car an 88 Sport Coupe that i found in a salvage yard. to get it re-titled i had to go through an inspection that basically verified it was safe and all emissions equipment was operational in stock form. i used all new parts in the emissions circuit other than the UFO valve of which i found a reasonably good one and took it apart and cleaned it... that being said this system has so many potential failure points just due to the number of parts that are affected by wear and tear i have already put my mod on that camaro as well as after 2 years of running it started having issues with fuel tank fill, etc... i would bet the diaphragm valve by the canister is bad but i just don't want the hassle so i went to my mod and problem solved

NoEmissions84TA

iTrader: (1)

Thanks so much for this. I will be keeping the valves by the vapor canister along with the associated vacuum lines, canister solenoid, vapor fuel lines, etc as you said, but replacing the UFO valve with the Tanks VVR valve. I don't want to be chasing any future problems. My 84 TA came with the LG4 CCC carb system with block mounted mechanical fuel pump and I added a small electric FP near the tank to give the fuel a push - the carb was running out of fuel during 1/4 mile runs. The car is over 25 years old, so no more emissions testing for me. I will be removing the ECM and associated components, but I will be keeping proper fuel tank venting.

Mr. IROC-Z

iTrader: (1)

I seem to have this issue as well. My car will randomly loose power and stall during hot weather. In the past year or so I have noticed more odor coming from the charcoal canister, and pressure release when I open the fuel cap. I cleaned out the fuel vent (UFO) and replaced the purge valve near the charcoal canister but I am still getting a fuel vapor scent from the charcoal canister. I will order this new fuel vent and hopefully it will resolve the issue! Thanks for letting us know about it!

Abubaca

iTrader: (3)

I was also getting a build up of pressure in the tank. I'll spare you the ongoing trials of what I tested, when, how, blah blah blah, but I had always intended to keep it all working. Ultimately my new Holley EFI set up won't control it, so I decided to remove it all . Found a few ideas on some kit car forums. Ultimately I took apart and cleaned the valve by the tank, and whipped up a home made charcoal filter and attached it to the line that went to the original charcoal canister. It just vents to the atmosphere, but the charcoal keeps the smell down. Since doing this I've had no "extra" pressure build up, no pressure purges, and no fume smell.

I know it's not for everyone, but I thought I'd throw it out there.

walnikj

I did this mod over the weekend. Seems to help but I still get a pump noise and some pressure release when I open the gas cap but not as bad or as much as before. However my car did stumble and shut down this morning on the way to work. It started up afterwards. I fear my year old Delco pump is going out.

walnikj

Did not workout so well for me. After 4 days with the tanks valve installed I removed it last night after the car shut down on me yesterday. It had fuel in the hose and on the valve itself.