2 hours ago, HusseinHolland said:

Looking a little further online for GM 80's versions - there is this brand new old stock one which certainly could be adapted. It has 2 diaphragms instead of one

eBay listing

Whoa!  You’d adapt it by just capping off the other diaphragm right?

Update: I took the entire vapor system apart and pressure tested each hose and the vapor tank by blowing into one inlet and capping the others with my hands; didn't taste great.

The result was finding all of the hoses and the tank hold air perfectly.  I put everything back together and when blowing from the front could still smell gas in the back.  I threw caution to the wind and cranked the belt clamps down to within an inch of their life and problem solved - no fumes.

 

Crank those clamps down boys and girls - case closed

On 4/6/2024 at 9:58 AM, chaseincats said:

Whoa!  You’d adapt it by just capping off the other diaphragm right?

apologies - I didn't see the question - yes, that is what I would do there. EDIT - actually I think you would add a vacuum line. The ports are listed PCV - Carb - Tank, so I think all three would be used. I'd look at a  GM schematic for the model it's intended for.

When you say belt clamps, you mean the hose clamps?

Edited April 26, 20241 yr by HusseinHolland

1 minute ago, HusseinHolland said:

apologies - I didn't see the question - yes, that is what I would do there.

When you say belt clamps, you mean the hose clamps?

Yeah, the hose clamps.  I changed the original clamps to a more modern style gates/belt clamp because you can get more clampage out of them

Edited April 26, 20241 yr by chaseincats

2 minutes ago, chaseincats said:

Yeah, the hose clamps.  I changed the original clamps to a more modern style gates/belt clamp because you can get more clampage out of them

OK - I typically replace line clamps with Oetiker clamps for anything that doesn't require routine service. 

Back on this topic - I pulled out a Volvo Cannister - I was looking at the hose from the vent line on the inner fender to the Cannister, and since it seemed to me there were signs (or rather smells) of gasoline on occasion, I figured I would try the Volvo (GM) Cannister at the same time

Identical fittings on this one - from a mid 90s 960

What I wasn't expecting was actual fuel in that metal vent line coming up the inner fender. When I pulled off the hose there was fuel all the way up at the hose. I presumed fuel vapor of course, but not fuel actually spilling out of the hose. No wonder I could smell gasoline there (given that they were cracks in the hardened hose).

I removed the gas cap and blew back through that hose to the tank to make sure it was clear. It is, so now that it's cleaned out I'll see if fuel accumulates in it as time goes by. Seems odd to me. 

11 minutes ago, HusseinHolland said:

Back on this topic - I pulled out a Volvo Cannister - I was looking at the hose from the vent line on the inner fender to the Cannister, and since it seemed to me there were signs (or rather smells) of gasoline on occasion, I figured I would try the Volvo (GM) Cannister at the same time

Identical fittings on this one - from a mid 90s 960

What I wasn't expecting was actual fuel in that metal vent line coming up the inner fender. When I pulled off the hose there was fuel all the way up at the hose. I presumed fuel vapor of course, but not fuel actually spilling out of the hose. No wonder I could smell gasoline there (given that they were cracks in the hardened hose).

I removed the gas cap and blew back through that hose to the tank to make sure it was clear. It is, so now that it's cleaned out I'll see if fuel accumulates in it as time goes by. Seems odd to me. 

Wow, did you give it a shot?

5 hours ago, chaseincats said:

Wow, did you give it a shot?

Hmm... somehow I forgot to take the pic AFTER I installed it 🤪.  I'll drive it around some tomorrow. The main thing I'm curious about is the fuel in the tank vent line.

Edited May 22, 2024May 22 by HusseinHolland

There should not be liquid fuel in that vent line. Wonder how that happened.

29 minutes ago, Captain Obvious said:

There should not be liquid fuel in that vent line. Wonder how that happened.

Indeed! There should be zero pressure in the vent side, so I don't see how liquid fuel could be drawn / pushed all the way up to the front. That would mean it had to pass through the vent canister also - seems implausible. Equally implausible for fuel to be fed through the charcoal canister, so it must have come from the gas tank somehow.  Also there is no check / rollover valve to be found on my 75.

Have you made changes to the way your tank venting is done? Anything other than replacing failed / leaky hoses?  I don't remember what you have done back there. 

And I think you are supposed to have the "check valve" device installed in the vent line running from rear to front. You're saying you don't have one?

42 minutes ago, Captain Obvious said:

Have you made changes to the way your tank venting is done? Anything other than replacing failed / leaky hoses?  I don't remember what you have done back there. 

And I think you are supposed to have the "check valve" device installed in the vent line running from rear to front. You're saying you don't have one?

So at the end of the day, here's what I did:

- pressure tested all of the hoses/vapor tank (by taking them all off and blowing in one end while plugging the others with hands/fingers

- replaced all of the original style clamps to gates belt clamps

- replaced the short hose that makes a u-turn on the filler neck (no idea why this exists)

- cut the ends of all the hoses off so they have a new tighter fit on the vapor tank

- cut about 6 inches off the main large hose that comes out of the gas tank and bought some new hose, then joined the two with a plastic joiner (a straight piece that you cram both hoses on.  Reason being that the hose held air when straight, but when curved (needed to plug in to vapor tank) there were small cracks

 

One thing I noticed was when you blow into the metal rail in the engine bay, it becomes noticeably more difficult to do so after doing all the above.

 

Hope that helps

-chase