Previous in Forum: New high speed engine?   Next in Forum: Steam Drum PSV Inlet losses
Close
Close
Close
12 comments
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25

Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 5:45 AM

I acquired a small gasoline-powered genset unit from a friend, who as it turned out had neglected it for some time. I worked on it, hoping to get it working during the seven-day power outage that followed the passage of typhoon "Odette." I have (I think) solved most of the problems, but here is a weird one. There is a fitting on top of the fuel tank that connects via a flexible tube to an auxiliary input on the air cleaner, so naturally I thought it was to take fuel vapor and feed it to the engine intake, rather than dissipating it in the atmosphere. But as I discovered when I drained the tank of fuel in order to de-rust it, the fuel filler forms a gas-tight seal, so another function of the fitting must be to break the vacuum above the fuel in order to allow it to flow.

But here's the thing - it doesn't seem to pass gas in either direction.

Before I chisel the damn' thing off and start over, I would like to be sure of what it is supposed to do.

The fitting belongs to a Coleman Powermate 3000 genset, and to anticipate early comments, I have tried to find a service manual on line, with no success.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 30951
Good Answers: 1727
#1

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 6:48 AM

I believe that is the rollover valve connection...supposedly shuts off gas if the generator becomes inverted somehow...

__________________
Break a sweat everyday doing something you enjoy
Register to Reply Score 1 for Good Answer
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#2
In reply to #1

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 11:15 PM

The arrow does point to the fitting that I am talking about, but how does it turn off the fuel? The hose connects to the air cleaner at the other end, and there is no electrical wiring connected with it.

Register to Reply
2
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 30951
Good Answers: 1727
#6
In reply to #2

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 2:26 AM

It's a simple ball and float setup, I suspect the ball has been stuck with gasoline residue in the closed position, maybe some carburetor cleaner would free it up....or possibly a generic replacement, as the part is discontinued....

__________________
Break a sweat everyday doing something you enjoy
Register to Reply Good Answer (Score 2)
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#8
In reply to #6

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 9:16 AM

Sounds like a good lead. I will spray carburetor cleaner into the thing tomorrow and see what happens.

Register to Reply
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#12
In reply to #6

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/30/2021 11:34 PM

No result with carburetor cleaner, no effect when trying to force air through the valve using my tire compressor. Next step is to drill out the blockage, then figure out the best way to fit a conventional breather.

Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 5989
Good Answers: 242
#3

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 11:16 PM

I have a vaguely similar unit (Firman 3600W), and without close examination, the Filler Cap on it also appears to form a gas-tight seal. Since you've brought it to my attention, I'm going to have to investigate how air gets into the fuel tank, but that will wait 'till daylight...

Again, without close examination, I don't see any comparable hose/connection to the top of the tank. This makes me suspect that SE gave the right answer, and mine does not have such rollover protection.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Power-User

Join Date: Feb 2020
Posts: 172
Good Answers: 4
#4

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 11:18 PM

https://www.ereplacementparts.com/powermate-pm0103008-3000-watt-portable-generator-parts-c-117046_130613_327647.html

__________________
The proper hardware will eliminate all theory.
Register to Reply Score 1 for Good Answer
2
Guru

Join Date: Jul 2016
Posts: 1050
Good Answers: 70
#5
In reply to #4

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/24/2021 11:58 PM

Not shown, but present, and obsolete, is Hose, fuel vapor, so I suspect that your vapor vent port is plugged with rust. My Coleman 4000W machine is from 1980s, fuel cap has a pinhole in it, and no vapor vent. I was able to order a replacement tank for it a few years ago, also all rusted, so shouldn’t be a problem. Or change the cap.

Register to Reply Good Answer (Score 2)
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#10
In reply to #5

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 9:23 PM

So, last resort - drill a small-diameter hole through the filler cap.

Register to Reply
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#9
In reply to #4

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 9:22 PM

And, sure enough, part 29 which is the one I'm looking at is called "valve, rollover." Damn' I love this forum.

Register to Reply
Guru

Join Date: May 2018
Location: Under the spreading Bunya Trees, South Burnett, Queensland, Australia
Posts: 611
Good Answers: 57
#7

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 4:37 AM

Maybe it is a breather for the tank to allow filtered air into the tank.

Stihl use a similar idea on their 2 stroke motors, but there the really fine sawdust gets into the fuel tank, good idea bad execution.

__________________
Hare today, goon tomorrow!
Register to Reply Score 1 for Good Answer
Power-User

Join Date: Mar 2010
Location: Negros, Philippines
Posts: 328
Good Answers: 25
#11

Re: Function of fuel vapor recycling [?] fitting for small gasoline engine

12/25/2021 9:25 PM

Funny how working on one piece of equipment reveals problems with others. I wanted to use my compressor (used mainly for inflating tires) to try to force air through the rollover valve. And the power cord is missing, and of course it's a custom type, not an ordinary power cord or extension cord.

It's here somewhere.

Register to Reply
Register to Reply 12 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

dkwarner (1); Haymaker (1); piolenc (6); rwilliams (1); SolarEagle (2); Stef (1)

Previous in Forum: New high speed engine?   Next in Forum: Steam Drum PSV Inlet losses

Advertisement