tank pressure

[james bennett]

I have a 85 corvette and I seem to have to much tank pressure when I remove the cap pressure is released. Is this normal?
I'm wanting to upgrade my laternator to a 120 amp or 140 amp. Which is the best ?
JIM

 

[Ken]

Sounds like you may be having plugging issues with your charcoal canister. I do not have my books with me so I can't troubleshoot it for you. Maybe someone else has experience with this and can help me out here.

 

[WhalePirot]

The charcoal canister

is fed from a vent just left of the fuel tank filler, through a fuel tank pressure control valve. It is NOT the purge valve atop the canister, which is ECM controlled to evacuate the fuel vapors when the engine is warm been running a while, above a certain road speed and throttle opening; then only with sufficient vacuum.

The canister should not be cracked or damaged; the extent of GM's guidance.

Functional test:
1- try blowing air through the lower hose on the purge valve. You should NOT be able.
2- applied vacuum to the upper tube should hold for at least 30 seconds, or the control valve or canister must be replaced. If it holds vacuum, blow again thru the lower tube. An increased flow i okay, else replace as above.

Lttle is said about the fuel tank pressure control valve, including where it is. It IS in line between the tank vent and the lower purge valve on the canister, and is controlled with vacuum from the throttle body. Yours may not operate.
mike

 

[KOPBET]

What do you mean by "too much pressure". Some pressure is normal. Around .7 to 1 psi.

I thought the purge valve and the control valve were both on top of the underhood canister on the '85 and the bottom of the canister is open. Am I wrong?

 

[WhalePirot]

purge valve and the control valve were both on top of the underhood canister

The manual does not state where the control vale is. The logical place would be atop the canister, with the purge valve.

The bottom of it is vented to atmosphere.

 

[james bennett]

tank pressure/alternator

Thanks for the reply on the tank pressure!! The valve is located next to the canister.
I must confess though, It is gone. This car is a Vette/viper with alot of modes on it. (NOTICE I SAID VETTE FIRST WITH CAPITAL LETTERS) I bought it last fall. I am trying to fix alot of BUMMED-UP things on it.
I knew that some pressure is normal but it should not sound like, opening a BEER can after it has been shook-up.
How about the alternator? I have heard that higher amps is needed because of all the electrical components like the MAF/BURN OFF SENSOR. It uses alot of juice.
THANKS,JIM

 

[WhalePirot]

alternator

I don't unddrstand why stock components would require more than a stock alternator.

Does a hi-power aftermarket audio system demand more juice?

 

[james bennett]

alternaor 120 or 140

The MAF/BURNOFF-sensor draws alot of amps and this is why higher amper. is better. with all the other ele. components along with it. I have heard that that the C-4's have had problems with this. Now I'm not an expert,just a tinkerer and I have this thig with making things better and then screwing it all up. That's why I am asking questions. Maybe somebody knows answers. What have you heard????

 

[Ken]

Re: alternator

Does a hi-power aftermarket audio system demand more juice?

Yep. Also, there are more and more electrical-draining devices being installed every day. You are aware that they are planning on upgrading the electricals in all new cars to carry more voltage, aren't you Mike?

The decision that needs to be made before the industry can progress further is how to address the need for more electrical power on-board the automobile. A number of groups such as the MIT Consortium, Forum Bordnetz, and SAE have agreed that 42 volts is a reasonable choice for the voltage of a new automotive electrical system. However, after picking the voltage level, the real choices have to be made.

For more reading, see: Automotive Engineering International Online

_ken