i have a 69 camaro 350. the car has been running bad sometimes and other times it runs good. i've been told its the timing, vacum modulator or the torque converter. i had a lot of pressure in my gas tank. when i took off the gas cap it sounded like i just unhooked a air line from a compressor. could a non-venting gas cap make my car run bad? when i release the pressure the car runs fine. thank you for any advice!
That's too much pressure. Get a new cap. My 69 makes the sightest hiss when I open it regardless of how much driving. I once had a car that I mistakenly plugged the vent. The tank started collapsing. You don't need that!
I figured I'd resurrect an old post instead of starting a new one...
I'm noticed the same problem with my 69 and a lot of pressure in the tank. I took off the cap and gas sprayed everywhere...I probably could have shot the cap out into the driveway the pressure was so great. It says it's vented but it's probably worn out.
My motor is a pre-87 with TPI and an external electric pump. Is there anything else that could cause something like this? I've heard of gas boiling if the exhaust is too close, but I'm pretty sure I'm alright there.
I guess I'll buy a new cap this weekend...and try not to be paranoid. I swear every spring something always goes wrong.
I would love to know why my "vented" gas cap does not vent. If I drive it around, the suction gets high enough to partialy collapse the tank. It has done this even with a new vented cap. I might have bought a defective cap but it was that way from the start and I drove it for years that way. Not sure what to do about it.
Torker just had his tank implode due to a faulty repro gas cap.
It bent the sending unit tube and float arm. A little air pressure fixed the tank but the sending unit needed to be removed for repairs.
We ended up brazing in a small galvanized tube (3/16" brake tubing) at the top of the filler neck so it faces rearward, and the end of the tube goes out behind the tank. The tube fits inside of the rubber sleeve. I'll likely to do the same thing to mine.
A vented cap allows for air to replace fuel. For emission reasons, the cap is designed to only allow air into the tank, but not allow fumes out. Atmospheric pressure plays a role...for instance if the atmospheric pressue drops a couple of points, the fuel tank can really burp when you remove the cap. Nothing to be alarmed about though...IMO.