Restrictor in vapor line from 72 gas tank?

[Gary S.]

More questions about my 72 vapor canister and line from the fuel vapor separator to the canister itself. I was vacuum testing what I assume are original hose going from the vapor separator on the fuel tank to the hard line and then back to a hose from the hard line to the charcoal canister. I was having difficulty getting a good draw on the vacuum hose from the hard line to the canister so I poked a long rod in there. A very hard obstruction prevented me from getting the rod through there. I managed to pull it out and it is a blue plastic restrictor with a pin hole in it. I am betting that the condition of the canister and hose tells me that they might be original.

Three photos tell the story:
1. shows the size of the blue plastic restrictor
2. shows the restrictor mostly out
3. shows the size of the hole in there.

Is this original and, if so, what is the purpose of restricting the draw on the vapor line from the fuel vapor separator?

Thank you again, and again.

It keeps getting weirder and weirder!

Gary

added. Btw, nothing in the AIM on this that I can see.

[Alan S.]

Re: Restrictor in vapor line from 72 gas tank?

Hi Gary,
It doesn't look familiar to me.
It looks similar to some of the plastic fittings (they're black not blue, but) that come with a Mity-Vac kit that are used as reducers/plugs/connectors for various size hoses that the tool might be hooked up to.
???
Regards,
Alan

[Gary S.]

Re: Restrictor in vapor line from 72 gas tank?

Alan,
I have two Misty Vacs and I have nothing resembling that in either kit. This has been in there for along time fro the looks of things.

[John H.]

Re: Restrictor in vapor line from 72 gas tank?

Gary -

That system (from the canister to the vapor separator at the tank) is a calibrated vacuum leak (somewhat like a PCV system), and I think the size of the orifice in that plastic insert establishes the maximum flow rate Engineering wanted to see in the system.

[Gary S.]

Re: Restrictor in vapor line from 72 gas tank?

Ok, John. That makes sense. This hose certainly appears original with the right amount of aging. I will put that plastic piece back into the hose and let it do its thing. I can see that pulling full vacuum off of the tank, without a restriction in place might cause some problems.

Thank you again,

Gary

[Alan S.]

[Gary S.]

Re: Restrictor in vapor line from 72 gas tank?

Alan, the insert, shaped like a mini thimble, more or less, was in the hose from the hard line to the charcoal canister. I could not tell it was there until I tried blowing on the line and got lots of resriction.

I am ready to reinstall the canister but I am certainly glad I asked the question. I actually thought it was someone's DIY idea.

[Joe L.]

Re: Restrictor in vapor line from 72 gas tank?

More questions about my 72 vapor canister and line from the fuel vapor separator to the canister itself. I was vacuum testing what I assume are original hose going from the vapor separator on the fuel tank to the hard line and then back to a hose from the hard line to the charcoal canister. I was having difficulty getting a good draw on the vacuum hose from the hard line to the canister so I poked a long rod in there. A very hard obstruction prevented me from getting the rod through there. I managed to pull it out and it is a blue plastic restrictor with a pin hole in it. I am betting that the condition of the canister and hose tells me that they might be original.

Three photos tell the story:
1. shows the size of the blue plastic restrictor
2. shows the restrictor mostly out
3. shows the size of the hole in there.

Is this original and, if so, what is the purpose of restricting the draw on the vapor line from the fuel vapor separator?

Thank you again, and again.

It keeps getting weirder and weirder!

Gary

added. Btw, nothing in the AIM on this that I can see.

Gary-------


GM #3993625, and after January, 1983, GM #3992372. Discontinued without supercession January, 1993.

[Gary S.]

Re: Restrictor in vapor line from 72 gas tank?

Joe,
Sorry, but I am a bit confused by your post. Are you saying that the restrictor is that GM part number?

Thanks. I am certain that just about everyone on this board owes you a big thank you.

Gary

[Joe L.]

Re: Restrictor in vapor line from 72 gas tank?

Joe,
Sorry, but I am a bit confused by your post. Are you saying that the restrictor is that GM part number?

Thanks. I am certain that just about everyone on this board owes you a big thank you.

Gary

Gary------


Yes, those are the part numbers for the restrictor.

[Alan S.]

[Gary S.]

Re: Restrictor in vapor line from 72 gas tank?

Alan,
It is nice to know that others are as curious as you and I. I set aside that "original" hose, after pushing out the restrictor, and said "let's just wait and see what the experts say". I got my new hose, after measuring the old and pushed in the restrictor. The hoses are hooked back up and, now that my new Quanta gas tank is here, I may actually fire this puppy up tomorrow afternoon.

Gary