mcrandrz

So I have never had a fuel tank vent valve. And after reading countess posts it seems theres no more production of them. Well. ****.

Everyone has some type of setup for it. What can I ghetto rig / use in place of one? I pulled 3 from a scrapyard and all 3 wouldn't hold any pressure. Right now my fuel is holding 30 psi which is right under spec. No driveability problems but the fact it won't hold pressure after key off is annoying.


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LarryD

How do you know it isn't holding pressure? Are you smelling gas especially when the tank is full?

I did a thread on here about the fuel tank vent valve (not the carbon canister filter vent, that is different). My thread talks about the valve mounted to the brake line bracket right in front of the differential. That valve is a two way valve. It opens very easy with a little suction to allow air into the tank when the fuel pump is drawing fuel. It requires a higher air pressure "blowing" on it to let the tank vent if is sits in the sun and the tank pressure when not running gets too high from the heat. I have gotten several out of wrecking yards and cleaned them with soap (Dawn) and water. They seem to work fine once cleaned thoroughly. I broke the clip getting my original out. I used a 10mm socket to slide over the end of the last one to squeeze the tabs together and slide it out of the bracket.

Mine had very bad gas smell when full. That was a leaking gas tank filler neck (that is a recall from 94 which is still valid). I could not see it leaking because of the heat shield between the muffler and gas tank. That "hid" the leak from view. The best way to check the leak is to remove the gas cap door, then remove the gas neck pocket.. Shine a flashlight down the filler neck and you can see where it joins the tank. That is where it leaks.. Mine was leaking for years and I proved that out when I pulled the tank to replace the fuel pump..

I would say that if you have low fuel pressure at the injectors, either the vent valve is plugged creating a "vacuum" in the tank that the fuel pump struggles against, your fuel filter inline forward of the differential is plugging up, or your fuel regulator mounted in the fuel rail is weak or failing. This info is just based upon what my car 92 3.1L has experienced.

Hope this helps..

mcrandrz

Thank you for the response but in the first 4 words I say I do not have a fuel tank vent valve. So. Its not the tank I replaced the tank myself. The lines have been flushed and tested. Brand new injectors. New pump.

Ohhhhhhh and I tested it using a pressure gauge. yes I smell gas at a full tank because its comes out of that damn line.

I have no vent valve so the line where its supposed to be is venting all my pressure.


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project89

iTrader: (1)

cap the vent line and buy a vented gas cap

LarryD

Ok, I just wanted to clarify about the vent valve and share what I learned and what I did after hours of research.... If it were me I would go get a used one out of a wrecking yard, clean it, test it, and put it on... That's what I did and it works fine on my car 92 RS 3.1L.. Cost me $2.00 at a Pull A Part yard.. I checked Camaros from 84 through 95 and they all had the valve or similar one.. They all seemed to work the same way as I pulled several (87, 89, 91 and 95).. They were all two way valves as I described and again are not designed to hold much pressure in either direction... I guess you could also try capping it and putting on a vented cap as suggested above.. Either would probably solve your fuel smell since you say you replaced the tank.. It likely will not solve your fuel pressure problem (I could be wrong and will stand corrected if that is the case).

As to your fuel pressure problem, I do not believe that the tank should be pressurizing to keep fuel up to pressure.. My car runs 38 psi on fuel pressure with the cap removed and no pressure what so ever in the tank (open to the air)... I don't claim to be an expert but when I seemed to have a problem with fuel pressure, it was the Fuel Pressure Regulator valve. Mine still wasn't holding the pressure for the spec 20 min but that might be due to the pump or the Pulsator (see below).

There is another possibility (again based upon my experience) relative to the fuel pressure issue. When I replaced my fuel pump I noticed that the instructions said there are two types of fuel pump. One uses a pump with a pulsator and one that uses a turbine pump without a pulsator. The Pulsator is supposed to stop fuel from surging back and forth in the fuel line with the injectors opening and closing. My car has a Pulsator. It is a box looking thing that sits between the fuel line and the fuel pump, inside the tank and directly on top of the fuel pump. It is a press fit on both the fuel line and fuel pump. I replaced mine at the same time as the fuel pump since it didn't seem to couple together tightly (possible fuel leak back into the tank dropping pressure?). I also noticed that the instructions said if you replaced the pump with a turbine style, that you are supposed to remove the Pulsator and replace it with a short piece of tubing.. I have no idea what the difference is between the two pumps.

Each person needs to make their own choice and decision as to how to deal with these issues since GM doesn't make the vent valve and neither does aftermarket.. As to the Pulsator, I was able to get a new one but those are starting to disappear as well...

caffeine

iTrader: (2)

I've replaced the pulsator with regular fuel injection hose on two cars with no issues. Supposedly it makes the pump a little louder.

fasteddi

iTrader: (2)

I did the same in my car also. No issues here, i could hear the pump a tad when i had the full exhaust on but it wasent much louder then before.

mcrandrz

replace a pulselator (lol I can't spell) when I changed fuel pump. Ill try the vent gas cap thing. Because right now I have a 24/7 vent that could be getting moisture in the new tank.


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LarryD

Yeah, I replaced my Pulsator since I could get a new one.. The new one was much harder to push on so maybe the old one was loose and was leaking causing the loss of pressure when the engine was off.. I should be able to check that by this weekend as I am putting it all back together so it can go to the Chevy dealer to replace the tank on the recall for free.. I suggested they just give me the new tank and I would put it in but they said due to liability, they have to put the new tank.. Oh well at least I am getting rid of the leaking tank.....

Marcos123

So I need to replace vent valve to and pick up a couple at the junk yard but how do you find out there working to you blow into them and the air is suppose to go through or it not suppose to go through please help

LarryD

When the car is running and drawing fuel out of the tank, the vent valve opens real easy. So, when I suck air through it, I got air through it with little effort. Going the other way, if the tank overpressures, then the valve will pop open.. Since it needs high pressure, blowing through it took some effort and then it suddenly popped open and vented.. Hope that helps... BTW, be careful not to get gas in your mouth if you do what I did to test it...

91rs-t-tops

I pulled my tank down the vent was already broke off and hanging there i just left it that way didnt figure it would hurt anything but i do smell gas all the time. So im gonna try blocking it off its got a vented cap on it already i bought it to replace the gas cap that was not there when i bought it. where is that bolt and the hose clamp ha ohhh i wonder if that has anything to do with having to crank it so many times in the morning to get to fire up after that starts every time you touch the key.