Canister Purge Valve ?

[Blt2Lst]

Can anyone tell me how to check the canister purge valve?

I have been getting gas odors under the hood recently and there are no external leaks. Also the car has been hard to start in the morning since getting my carb rebuilt.
I had the carb back to the shop that did the rebuild thinking the seat was leaking thus draining the fuel bowl overnight. It still has the problem.
I called the carb shop and he said it may be the purge valve or canister.

Anyone have any ideas?

[j cAT]

Originally Posted by Blt2Lst

Can anyone tell me how to check the canister purge valve?

I have been getting gas odors under the hood recently and there are no external leaks. Also the car has been hard to start in the morning since getting my carb rebuilt.
I had the carb back to the shop that did the rebuild thinking the seat was leaking thus draining the fuel bowl overnight. It still has the problem.
I called the carb shop and he said it may be the purge valve or canister.

Anyone have any ideas?

locate the cannister control valve ..gas in it or smell very strong gas odor ? take it off then check the lines esp the one that goes to the carb see/ smell gas ? this means its bad..diaphram ruptures causes flooding and will melt down the cat converter !


check the cannister if its loaded with gas that will also need replacement...

[Blt2Lst]

Originally Posted by j cAT

locate the cannister control valve ..gas in it or smell very strong gas odor ? take it off then check the lines esp the one that goes to the carb see/ smell gas ? this means its bad..diaphram ruptures causes flooding and will melt down the cat converter !
check the cannister if its loaded with gas that will also need replacement...

Sounds like a good place to start.
It just seems a little odd that this problem started after the carb was rebuilt.
Could just be a coincidence, stranger things have happened..

Thanks

[caffeineaholic]

If it's non-ecm controlled then I may have the illustration you need in order to test it. Mine actually went bad a few months back. I had to replace the evap canister and also the valve. The shop manual for my car calls it a Canister Control Valve. It has four ports on it.

[Blt2Lst]

Originally Posted by caffeineaholic

If it's non-ecm controlled then I may have the illustration you need in order to test it. Mine actually went bad a few months back. I had to replace the evap canister and also the valve. The shop manual for my car calls it a Canister Control Valve. It has four ports on it.

My car also has the CCV with four ports.
I just found the diagnostic procedure in my factory service manual for those components and will test.
What were your symptoms that led to you checking yours?
Did it trigger a CEL?

[caffeineaholic]

A CEL was not triggered (probably because I caught the problem soon and did not drive for extended periods which may cause the ECM to detect a rich mixture via the o2 sensor).

I also could smell the strong odor of gas and my evap canister was ruined (felt nearly ten times heavier than a new one). I tested my CCV and the diaphragms were broke just like j Cat said.

I also had some driveability issues -- I think the car just ran rough and surged (more than normal).

It only cost me 36$ for a new evap canister (Autozone) and I believe 15$ for a new CCV (amazon.com I think).

[Schrade]

Over-filling the gas tank can cause gas to draw into the cannister.

The purge cycle is not electronic on a '75 I don't think - vapor accumulation is passive. That means tank pressure makes vapors travel the tube to the cannister charcoal and get stored til the intake decides to purge. I don't know what triggers the purge, unless it's continuous, as the motor runs.

IF IT IS continuous, then you can pull the vac line from the intake that goes to the cannister, and see if you can draw on it. If you cannot, disconnect the other end from the cannister, and see if THAT hose is blocked.

If it is, then the cannister ain't purging, and the gas is stuck not purging, and that's what you smell.

2 'IF's there - that's all I know on that one...

[Blt2Lst]

Originally Posted by cbec1999

Over-filling the gas tank can cause gas to draw into the cannister.

The purge cycle is not electronic on a '75 I don't think - vapor accumulation is passive. That means tank pressure makes vapors travel the tube to the cannister charcoal and get stored til the intake decides to purge. I don't know what triggers the purge, unless it's continuous, as the motor runs.

IF IT IS continuous, then you can pull the vac line from the intake that goes to the cannister, and see if you can draw on it. If you cannot, disconnect the other end from the cannister, and see if THAT hose is blocked.

If it is, then the cannister ain't purging, and the gas is stuck not purging, and that's what you smell.

2 'IF's there - that's all I know on that one...

Good point on over filling gas tank, no more topping off like i started doing..

I just tested the CCV and it was faulty, there was also some fuel inside the valve as jcat mentioned.
The Vapor Canister seemed a little heavy also and the filter underneath was caked with crud although no external gas leaks.
Just ordered new parts, hope it fixes the problem.

[j cAT]

Originally Posted by Blt2Lst

Good point on over filling gas tank, no more topping off like i started doing..

I just tested the CCV and it was faulty, there was also some fuel inside the valve as jcat mentioned.
The Vapor Canister seemed a little heavy also and the filter underneath was caked with crud although no external gas leaks.
Just ordered new parts, hope it fixes the problem.

they fail every 40,ooomi...got to check this , when you tune up every yr...

[mike561]

makes me wonder why they disconnected the line to my canister on my '83 that went to the CCV, pretty much all the emmisions stuff like that was removed before i bought the car (ccv, air pump, air injection tubes that went into the headers) i still get a slight odor of gas every now and then. you think its worth checking your canister even though its only connected to the gas tank now? thats really the only thing i've never checked since ive had the car for three years now lol

[j cAT]

Originally Posted by mike561

makes me wonder why they disconnected the line to my canister on my '83 that went to the CCV, pretty much all the emmisions stuff like that was removed before i bought the car (ccv, air pump, air injection tubes that went into the headers) i still get a slight odor of gas every now and then. you think its worth checking your canister even though its only connected to the gas tank now? thats really the only thing i've never checked since ive had the car for three years now lol

these were disconnected,,, even I disconnected my CCV for a time because this part WAS a dealer only part [expensive ] ...until the new/good CCV could be installed..

also the ccv is used to purge the cannister of gas vapor...
as long as you don't overfill the fuel tank and then quicly park the vehicle this vapor should not be that great...

if that CCV fails good by cat converter/ ...melt down ..
you won't pass emissions test if CCV is ruptured..

[Blt2Lst]

Originally Posted by j cAT

you won't pass emissions test if CCV is ruptured..

It's funny, but my car did pass emissions recently with the bad ccv and vapor canister.
I only checked it because of the fuel odor and hard cold starting problem i was encountering after having the carb rebuilt.
Go figure..

[j cAT]

Originally Posted by Blt2Lst

It's funny, but my car did pass emissions recently with the bad ccv and vapor canister.
I only checked it because of the fuel odor and hard cold starting problem i was encountering after having the carb rebuilt.
Go figure..

thats because you have the olds 307cu ....this is different ...not as bad as the 305 cu chevy engine vapor control ....when that ruptures it is a lot of liquid fuel sucking into the carb base ...black smoke ....the engine will shake when running ..

[EngineandJuice]

I had a heavy gas odor coming from my car that i smelled a lot when sitting at lights and when i would get to my destination and get out the car. I couldn't find any trace of a leak replaced teh canister and valve and all that stuff even replaced the rubber hoses on the fuel pump. The reason i was missing the leak is because when i would shut the car off by the time i got out and started to check the leak all the fuel had evaporated. it wasn't until i changed the hoses to the fuel pump and started the car and checked with the car running that i realized the leak wasn't coming the pump but from the hard line leading from the pump to the carb. Come to find out the line was vibrating against the alternator bracket which had cut straight through it. Replaced that and no more fuel odor.

If the fuel line wasn't suppose to be running near the alternator then don't ask me how it got there probably from the Edelbrock install. The slit in the line was pretty much halfway down the line making even harder to locate until i seen the fuel leaking back to the fuel pump.

[caffeineaholic]

My fuel line also ran behind the alternator, I eventually had to just replace it with a good fuel/emissions rubber hose instead -- although I should probably get it done right and bend a new metal pipe for it...

As far as I know it was never replaced or moved before; it probably was always set up behind the alternator.